When progressive political commentator Keith Edwards recently turned the New York City Pride March into a two-hour livestream of queer joy, he put a name on what he was doing. The GLAAD-backed broadcast was built, in part, for people watching alone in states where Pride can feel dangerous. “One of the most radical things you can do in a moment of extreme fear and a moment of authoritarianism,” he told The Advocate, “is to experience joy and happiness.”

Weeks earlier, RuPaul had posted that the only response to fascism was to party and dance, and was sharply criticized for it. Two moments, weeks apart, but the same uneasy question beneath both of them: Is joy resistance? Or is it what we call avoidance when we want avoidance to sound principled?

In a country where LGBTQ+ people are watching their rights stripped away in statehouses, drag performers turned into political targets and trans people used as campaign-season fuel, “go dance” can sound almost heartless. But queer people have had this argument before.

In a 2013 Washington Blade essay about coming out during the AIDS crisis, Dave Purdy remembered older gay men telling him it was wrong for his generation to dance, party or enjoy themselves while their gay brothers were sick and dying. He and his friends rejected that view. For them, the dance floor was not an affront. It was survival, self-love and something close to church.

During the AIDS crisis, gay nightclubs were not merely places to escape. They were informal mutual-aid networks, grief rooms and information exchanges. They were places where bodies marked by fear could breathe, move, touch and feel alive again. When the state was slow to act, conservative preachers’ sermons were cruel and much of the country looked away, these spaces helped people endure.

I know because, in the early 1990s, I ran one of those clubs on Long Island.

The club was loud, crowded and alive in the way only a queer room can be when the world outside has made everyone inside feel disposable. People arrived carrying the private weight of family rejection, HIV panic, religious shame, police harassment and the everyday terror of being seen too clearly in the wrong place.

Then the bass would start. The lights would move. Someone would laugh loudly near the bar. A drag queen would cut through the room like a flare. For a few hours, fear did not vanish. It changed shape. It became bearable.

To outsiders, nightlife often looks like escape. Sometimes it is. There are worse things than needing to escape a world trying to crush you. But queer clubs were never only about forgetting. They were places where people remembered each other: who was sick, who had disappeared, who had a new doctor, who was pretending to be fine.

I saw that attention at work every night. Power did not only sit in the office or behind the bar. It lived in the queens who could read a face from across the room, the regulars who noticed an absence and the staff who could feel the room change before anyone else did. That was vigilance. Not paranoia. Not panic. A communal intelligence.

The dance floor was not where the crisis disappeared. It was where the living found one another inside it. That is the part America often forgets. Survival is not only the refusal to die. It is the insistence on remaining human while threatened.

Bars hosted fundraisers. Drag performers passed hats. DJs, bartenders, door people, lovers, ex-lovers, activists and friends formed networks that were not always formal but were often lifesaving. In Orlando, the Parliament House Motor Inn, a gay resort and nightclub, became a common site for AIDS fundraisers in the 1980s and 1990s. This detail matters because it collapses the false divide between pleasure and care. A place outsiders might dismiss as decadent was also where money was raised, grief was gathered and a frightened community turned nightlife into a lifeline. Chosen family was not a slogan. It was logistics.

Research has linked synchronized movement with social bonding and increased pain thresholds, while studies of dance and movement therapy have found benefits for depression, anxiety and interpersonal functioning. What outsiders now call resilience was, for us, simply the nightly practice of keeping one another going. 

That is why the word “joy” can be misleading if we make it too soft. Joy in queer nightlife was and is sweaty, sexual, improvised, defiant, sometimes reckless, sometimes holy. It did not erase grief. It gave grief somewhere to go.

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None of this means dancing is enough. A party will not stop authoritarianism. A drag show will not repeal anti-LGBTQ legislation. A nightclub cannot replace courts, organizing, voting, or protest. Joy without vigilance can become anesthesia. Joy without community can become branding. Joy without politics can become escape for those privileged enough to leave others behind.

But the answer is not to dismiss joy. It is to understand what kind of joy has power — a lesson America needs now.

The country is confronting a crisis. We are politically exhausted, increasingly isolated, distrustful of institutions and surrounded by reasons to be afraid. More people are discovering that they can follow every headline, understand every threat and still have nowhere to put the fear.

Queer nightlife offered one answer, imperfect but profound: Put the fear in a room. Let it breathe alongside other people’s fear. Let the body remember that it is more than a battleground.

The joy created in queer nightlife was collective. It required a room. It required witnesses. It required people watching the door, watching each other and noticing when the mood shifted before trouble arrived. Pleasure and protection had to coexist.

That was the real survival infrastructure; not joy by itself, but joy attached to community and vigilance.

To survive a hostile world, people need pleasure and community, yes — but they also need history. They need to know what they are up against and what others survived before them. They need to care for each other while they watch the door. They need to build systems that do not depend on the benevolence of institutions that may never come.

The pushback against “party and dance” landed because it sounded like the whole plan. It cannot be the whole plan. But it can be part of one.

We did not dance through the AIDS crisis because things were fine. We danced because everything was not fine, because the body needed proof it still belonged to the living. We danced because grief without community becomes isolation, and isolation is where despair does its best work.

Dancing didn’t solve the crisis, but it helped us survive long enough to keep fighting.

This is not nostalgia. It is instruction.

The post When joy was resistance on the dance floor appeared first on Salon.com.

Wide Release Date for MagnaMax for Small Knifemakers

MagnaMax will be on sale May 1st, 2026 at 9am on Niagara Specialty Metals’ online store: https://nsm-ny.com/shop/

You can create an account beforehand so that you are ready to buy once the steel goes live. We made the following commercial to get pumped for the release:

Intro

I wrote an article (and created a video) about MagnaMax properties a few months ago. So I won’t be rehashing all of the properties here. Basically, MagnaMax is designed to have enhanced wear resistance and edge retention vs MagnaCut with similar corrosion resistance and hardness potential.

You will also see in the chart above that MagnaMax offers superior toughness and edge retention to the popular M390 and 20CV. It is very difficult to improve both of these properties at the same time, so this is a big improvement. It also maintains similar toughness to grades CPM-154, S35VN, and Vanax, which were formerly the toughest PM stainless steels prior to MagnaCut. So it offers a significant edge retention improvement to those grades, which have had a reputation for good properties in the past.

That property summary article did not have specific heat treatment recommendations because I was waiting on the final material. The initial heat of steel had carbon on the low end of the specification, so it wasn’t as representative of the average material as I wanted. No change was made to the target composition or the specification, it just landed at the lower end for carbon. So now that I have received and tested material closer to the midpoint of the specification I performed a more comprehensive set of tests. Knifemaker Matthew Gregory helped to make the majority of the toughness coupons.

High Level Heat Treatment Summary

Before we get into all of the details I can give a simple summary so you don’t get lost.

With Cryo:

Austenitize 2100-2250°F (1150-1230°C). The baseline temperature for good properties is 2150°F (1175°C).

Plate quench for faster cooling and slightly higher hardness.

After cooling to approximately room temperature, place immediately in liquid nitrogen. The amount of time it sits in the liquid nitrogen doesn’t matter that much, it just needs to reach the temperature. An hour is fine. What does matter is not wasting time before putting it in the liquid nitrogen. You don’t need to check the hardness beforehand.

Temper 300-450°F (150-230°C) twice for two hours each time. 350°F (175°C) is a baseline temperature for good properties.

Without Cryo:

Use your household freezer. It is a myth that it doesn’t have any effect. There is no reason to do no cold treatment. Everybody has or can get a freezer. Dry ice is even better, but despite being about 100°F colder than a freezer often behaves closer to a freezer than to liquid nitrogen.

Austenitize 2050-2100°F (1120-1150°C). 2100°F (1150°C) is a good temperature. It might be possible to go somewhat higher but I worry about excess retained austenite.

Plate quench for faster cooling and slightly higher hardness.

After cooling to approximately room temperature, place immediately in the freezer or dry ice. The amount of time it sits in the freezer doesn’t matter that much, it just needs to reach the temperature. An hour is fine. What does matter is not wasting time before putting it in the freezer. You don’t need to check the hardness beforehand.

Temper 300-450°F (150-230°C) twice for two hours each time. 350°F (175°C) is a baseline temperature for good properties.

Austenitizing hold times:

The required hold time changes with temperature. This is the soak time required after the piece reaches the temperature. It rarely hurts to add extra minutes, it is more common to have an issue with undersoaking.

2050°F (1120°C): 20 minutes

2100°F (1150°C): 15 minutes

2150°F (1175°C): 10 minutes

2200°F (1205°C): 5 minutes

2250°F (1230°C): 5 minutes

Hardness and Cryo

I first made a series of coupons to test the hardening response, including with the addition of a freezer or liquid nitrogen treatment after quenching. I used the soak times in the section above.

You can see that with no cold treatment the peak hardness was 2050°F (1120°C) after tempering at 300°F (150°C). Hardness drops with higher temperatures from excess retained austenite. Hardness rose when using liquid nitrogen all the way to 2250°F (1230°C). It would be unlikely to keep rising much beyond this temperature and the possibility of melting grain boundaries starts to become more of a danger. The freezer also rose all the way up to 2250°F but to a lesser extent. Because the increase was small beyond 2100°F (1150°C) this is why I limited my recommendation for the freezer to that temperature. That makes me think both the retained austenite and hardness of the martensite were increasing beyond that temperature, leading to relatively flat behavior. Excess retained austenite can lead to worse sharpening behavior when deburring. Overall this hardening response is not radically different than MagnaCut.

Nothing too crazy showed up in the tempering. You can see that a cold treatment leads to less hardness loss in tempering. Compare 2050°F with and without a cold treatment, or 2100°F with liquid nitrogen vs the freezer. Note that I have a single curve for both freezer or liquid nitrogen from 2050°F, and this was because the two were sufficiently similar to have a single line. Plus don’t want to make the chart too busy.

You will also notice that the hardness reaches an initial minimum at 600°F (315°C) and then rose to a secondary peak around 900°F (480°C). This is known as “secondary hardening.” I don’t recommend tempering in that range, especially with stainless steels, because it reduces corrosion resistance. For example see two Vanax coupons below, both sprayed with 1% saltwater. The one of the left was tempered at 400°F (200°C) and the one on the right was tempered at 1000°F (540°C).

Toughness

We also tested a series of charpy toughness coupons for this heat of MagnaMax. I used my standard coupon which is quarter size (2.5 x 10 mm) and unnotched. Three coupons were tested for each condition. We used liquid nitrogen in the heat treatment of all of these coupons directly after the quench. We used austenitizing temperatures of 2000-2250°F (1095-1230°C) and tempering temperatures of 300, 350, and 450°F (150, 175, 230°C).

The hardness was slightly lower than the small hardness coupons I showed results from before:

Looking at the resulting toughness, it rose from 2000 to 2050°F (1095 to 1120°C), was relatively flat up to 2200°F (1205°C), and then dropped somewhat up to 2250°F (1230°C). This is why I recommended a baseline austenitizing temperature of 2150°F (1175°C) as this appears to be roughly the peak hardness-toughness, though an argument could also be made for 2200°F (1205°C), in part due to a couple of the 2150°F results being on the low end and a couple of the 2200°F being on the high end. This is likely due to statistical variability of testing.

You can also see that toughness increases with tempering temperature as we would expect, which also corresponds to a hardness decrease. Lower hardness generally correlates with higher toughness.

There was a greater increase in toughness between 300 and 350°F (150-175°C) than between 350 and 450°F (175-230°C), which is why I recommended 350°F (175°C) as the baseline tempering temperature.

Hardness-Toughness Balance

But what we would like to maximize is the highest toughness for a given hardness. So I plotted hardness vs toughness below.

You will notice that the maximum hardness-toughness combinations were generally 2150-2200°F (1175-1230°C) and tempering at 350-450°F (175-230°C). The exceptions include: 1) 2100°F (1150°C) with 450°F (230°C) because that combination gave the best properties for lower hardness. And 2) For maximum hardness you need 2150-2250°F (1175-1230°C) in combination with the minimum tempering temperature of 300°F (150°C). I next overlaid those best heat treatment conditions on top of the similar non-stainless steels K390, Vanadis 8, and CPM-10V:

Erasteel MM#1 is the first heat that was shown in the prior article about MagnaMax properties, and Erasteel MM#2 is the final tested material above. You can see that both have a similar hardness-toughness balance, though the new one is skewed to somewhat higher hardness, as expected from more carbon. You will also see that the toughness is very similar to K390 and Vanadis 8, an excellent result given that MagnaMax is a stainless steel with similar wear resistance. So we greatly improved corrosion resistance over those steels while maintaining their other properties. I next plotted those hardness-toughness values vs other stainless powder metallurgy steels:

You can see that MagnaMax has superior hardness-toughness than virtually all of the powder metallurgy stainless steels apart from MagnaCut. This includes steels with a good reputation for toughness including Vanax, XHP, S35VN, and CPM-154. And below I have the more complete graph of stainless steels which is a bit busy:

Corrosion Resistance

I compared the final higher carbon version of corrosion resistance to the earlier and both passed the 1% saltwater corrosion test. Showing a picture of two clean samples isn’t very interesting, so here is the earlier image of MagnaMax vs other steels:

Each of those was austenitized from 2150°F (1175°C). MagnaMax (and MagnaCut) were designed for all of the chromium carbides to be dissolved around 2050°F (1120°C). After the chromium carbides are dissolved the corrosion resistance doesn’t appreciably change with even higher temperatures. This is different than most other stainless steels which have chromium carbides all the way up to the melting temperature. But using even higher than 2050°F does provide some factor of safety, better ensuring the chromium carbides are fully dissolved.

The other main factors for corrosion resistance are quench rate and tempering temperature. I mentioned in the tempering section that tempering above about 750°F (400°C) leads to a reduction in corrosion resistance and I showed a test with Vanax to illustrate that. Quenching isn’t an issue unless it is very slow, which leads to carbides precipitating on the grain boundaries which can reduce corrosion resistance.

Edge Retention

The primary factors for edge wear resistance are carbide volume, carbide hardness (controlled by type), and steel hardness. While the carbides are very important when comparing different steels, there is less of an impact within a given steel. It is true that austenitizing higher dissolves a bit more carbide but this effect is generally drowned out by the increase in hardness. So in general, achieving a higher hardness results in greater edge retention, and there isn’t much point in worrying about the exact austenitizing and tempering temperatures that were used to get there. I have the graph below of CATRA results I tested previously to show where MagnaMax lands and the effect of hardness on the results:

Summary and Conclusions

So I have shown the majority of the heat treatment data that I generated and my reasoning for the different recommendations. I am overall happy with how the heat treatment response ended up. If you want to see the simplified heat treatment recommendations, scroll back near the top where it said “High Level Heat Treatment Summary.” Hopefully that is simple enough for everyone. If not then ask questions in the comments. MagnaMax will be on sale May 1st, 2026 at 9am on Niagara Specialty Metals’ online store: https://nsm-ny.com/shop/

The post How to Heat Treat MagnaMax Steel appeared first on Knife Steel Nerds.

Crucible, Niagara, Erasteel, and MagnaCut

In case you haven’t been following steel news, Crucible Steel went through a bankruptcy and no longer exists. I interviewed Bob Shabala of Niagara Specialty Metals about this transition several months ago. Niagara is the company that purchased ingots from Crucible and would hot roll, anneal, and distribute them to knife companies and steel suppliers. They have also recently started a new online store to better sell directly to individual knifemakers. Niagara has managed to keep production going for a wide range of Crucible (and other) knife steels, including:

MagnaCut, CPM154, S30V, S35VN, S45VN, S90V, 3V, 4V, CruWear (NSM Wear), 154CM, 20CV, M4, CPM D2, D2, 440C ESR, 416SS, 6-4 Titanium. MagnaMax should be available in early 2026.

Erasteel purchased the rights to Crucible Steel trademarks. Erasteel is headquartered in France, but its powder metallurgy production is in Sweden. Niagara worked with Erasteel to retain the exclusive rights to purchase MagnaCut ingots and sell the steel to knifemakers and knife companies. Erasteel produces very high-quality powder metallurgy steel. Bob Skibitski was the head of the powder metallurgy steel production at Crucible Steel for 20 years and was hired by Erasteel. He reports that Erasteel production yields higher-quality, “cleaner” steel. You can read his thoughts in an article on Niagara’s website.

Video

There is a video version of this article:

Previous Testing of European Powder Metallurgy Steels

I have published two studies before comparing manufacturing from different powder metallurgy companies. One compared M390, 20CV, and 204P (with the somewhat different Elmax thrown in). The other compared Z-Wear (same as CPM-CruWear) between Crucible and European production. With the M390/20CV/204P study I found the biggest difference between manufacturers was the oxygen content. Oxygen is an impurity and it leads to oxide inclusions that are detrimental to properties. This is something advertised by companies like Bohler-Uddeholm, that their process is “cleaner” and leads to fewer oxides. However, the toughness of the grades was identical, perhaps in part because the carbide content is quite high and carbide size of M390/20CV/204P are basically the same. Even though Bohler advertises a finer powder size, the carbide size is mostly a result of carbide “coarsening” during high-temperature processing after the powder is made, rather than differences in powder size.

M390

20CV

So the carbide volume, carbide size, and resulting toughness are primarily controlled by the composition and method of manufacture (powder metallurgy) rather than the quality of the production. If the oxides are smaller and in a lower volume than the carbides, then the limiting factor for toughness is the carbide, and so oxide inclusion content doesn’t much come into play.

In the Z-Wear study I thought there might be more of an effect of oxide inclusions than the M390 because it has significantly lower amount of carbide. However, the two steels tested relatively similarly in terms of toughness:

In this case the European-produced version of Z-Wear had slightly higher toughness but it was also at a lower hardness, giving it a slightly worse hardness-toughness balance. In general I called them equivalent in the article. I actually suspect that Zapp had accidentally mixed up the labels of the steels because the oxygen content was lower in the steel that was labeled as “USA” once it was delivered to me. That would mean the European steel had a slightly better hardness-toughness balance, rather than the USA Crucible version.

USA vs European Z-Wear that might have been mislabeled before they were sent to me

Dialing in the Composition for Erasteel MagnaCut

With switching over to Erasteel for MagnaCut production we had several things we needed to figure out. One that might be surprising to people is that steel composition testing is highly dependent on calibration of the instrument and which technique is used. For example, there were significant differences in composition measured between grades in the M390/20CV/204P study and the Z-Wear study. This is not always clear because there is some distribution of composition in manufacturing. If the target is 10% chromium, there is some acceptable range by the manufacturer like 9.5-10.5% Cr. So you can’t measure just one example from different manufacturers and know what the offsets are. So we took pieces of MagnaCut from multiple Crucible “heats” and sent them to Erasteel so that they could have appropriate offsets to match the Crucible material. We will continue to monitor the performance of the new MagnaCut material because of the distributions. If heats on the low end or high end of certain elements are not performing well in one performance category or another we could shift the target or tighten the acceptable ranges. This is the side of development and quality control that is often not seen by the end customer and is probably not very exciting.

Erasteel vs Crucible MagnaCut

One very important part of MagnaCut is its high corrosion resistance. So I tested with my standard 1% saltwater spray test. Most stainless knife steels will see some rust spots with this test. In this case neither the Crucible or Erasteel material showed any rust spots:

I also tested the hardening response. For a given heat treatment the hardness was very similar, perhaps the Erasteel material was slightly higher:

Surprisingly (based on the Z-Wear and M390 results), the toughness of Erasteel MagnaCut was significantly higher:

You can see that the Erasteel MagnaCut was significantly higher, matching AEB-L at ~62 Rc, and exceeding it at ~64 Rc. I wouldn’t necessarily extrapolate that up to AEB-L levels at 60-61 Rc but in that hardness range it was very good. Comparing with non-stainless steels this also makes Erasteel MagnaCut look more competitive:

While Crucible MagnaCut was a bit below the best results of CPM-CruWear and Z-Wear, the Erasteel version matches or exceeds it. In my knife steel ratings I had given MagnaCut a “7” for toughness and CPM-CruWear an “8,” so this is exciting. MagnaCut has a similar carbide volume to CPM-CruWear but has even smaller carbides so it was always a bit disappointing that the measured toughness wasn’t matching it. Perhaps this was a case where oxide inclusions were reducing toughness slightly in the Crucible version. Erasteel MagnaCut even roughly matched the new Bohler K888 steel, advertised for its high toughness, and tested better than steels like Vanadis 4 Extra. One thing to note is that toughness differences are basically on a “log scale,” meaning that differences at small values are bigger than those at large values. So the difference between 5 and 10 ft-lbs is about the same as between 10 and 20 ft-lbs.

One difference I noted in toughness testing is that using an austenitizing temperature of 2150°F (1175°C) and then tempering to desired hardness led to better toughness than lower austenitizing temperatures. With Crucible MagnaCut the optimum property balance was with 2050°F (1120°C).

You can see that for a constant toughness of ~20 ft-lbs that the hardness can be higher for that same toughness with a higher austenitizing temperature, about a 2.5 Rc increase.

Summary and Conclusions

The MagnaCut now being produced by Erasteel matches or exceeds the properties of the previous Crucible version. Specifically the toughness showed an improvement. We will continue to monitor the properties of the new material to ensure the performance meets expectations with the new manufacturing partner.

The post Testing Erasteel MagnaCut (vs Crucible Original) appeared first on Knife Steel Nerds.

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Video

Here is the video version of the following information:

Misunderstandings about Hardness and Corrosion Resistance of MagnaCut

I have been seeing a disturbing number of comments around the internet saying something like the following: “Larrin says that 60 Rc MagnaCut has better corrosion resistance than 64 Rc MagnaCut, so there are different hardness levels for different applications.” I have never said such a thing. It is true that there are different levels of hardness for various applications, but hardness does not dictate corrosion resistance; therefore, it is not one of the parameters by which they would make this decision. I have a video where I have talked about the pros and cons of higher and lower hardness. How you heat treat a given steel can affect its corrosion resistance but a whole range of hardness values can be achieved with both good or bad heat treatments. I will give a variety of examples for this. A separate but related topic is about how hard different steels can be heat treated to when related to their corrosion resistance. For example, the very corrosion resistant Vanax and LC200N top out around 59-61 Rc. I will explain why they don’t get any harder and why this is partially due to those steels having very high corrosion resistance.

Chromium and Corrosion Resistance

When iron is in a corrosive environment it forms rust – an iron oxide. If you add chromium to iron, the corrosion resistance is increased the more chromium you add. The chromium forms with oxygen to make a passive film at the surface which prevents rust from forming:

The following chart shows an old classic study [1] of corrosion rate of steel in high humidity environments. You will see that the corrosion rate went down with increasing chromium until about 12% Cr. Sometimes the cutoff for a steel being “stainless” is given as 10.5, 11, or 12% chromium. There isn’t any real agreement as far as I can tell. But corrosion resistance will increase with even greater amounts of chromium; it isn’t an on/off after some arbitrary cutoff.

Data adapted from [1]

Heat Treating and Corrosion Resistance

In the annealed (soft) state stainless steel is not yet stainless. When a knifemaker or manufacturer receives steel it is in this annealed condition so it is easy to drill, grind, machine, etc. Most of the chromium is in the form of carbides in the steel. When the chromium is tied up with carbon as a carbide it cannot form the chromium oxide layer at the surface.

There are three major steps to heat treating: austenitizing, quenching, and tempering.

Austenitizing

During austenitizing the steel is heated up to a high temperature and then held, allowing the chromium carbides to be dissolved (or partially dissolved) to put more chromium in solution so that the chromium oxide passive layer can be formed. Below shows the increase in chromium vs austenitizing temperature for Elmax and Vanax:

So one of the key variables for corrosion resistance is the austenitizing temperature because heating it hotter means more chromium in solution. However, the amount of chromium in solution is also controlled in part by the composition. The chromium in solution for Elmax at a very high temperature of 2200°F (the datasheet recommends no higher than 2010°F) is still below Vanax when it is austenitized at 1800°F (well below what the datasheet recommends). Austenitizing at a higher temperature also leads to increased hardness, so in that way higher hardness can sometimes mean improved corrosion resistance.

Quenching

During quenching the steel is rapidly cooled to form the hard phase of steel, martensite. Martensite formation is controlled by temperature rather than time. There is a “martensite start” temperature and a “martensite finish” temperature. In some cases martensite finish can be below room temperature and in that case the steel does not fully transform, meaning some austenite remains in the steel. This is called “retained” austenite. If there is too much retained austenite the hardness is reduced in the steel, and also the edge performance is bad and the knife would be very difficult to sharpen. One of the major factors for martensite start (Ms) and martensite finish (Mf) temperatures is the carbon content, as shown in the chart below.

With higher austenitizing temperatures and more carbide being dissolved, this does not only put more chromium in solution but also more carbon, as seen in this chart of Vanax and Elmax. Or in the case of Vanax, I included the carbon and nitrogen, since nitrogen also contributes to hardness in a similar fashion to carbon.

All of the above happens as long as the quench is sufficiently fast to avoid other competing transformations that will occur with slow cooling. Carbides can precipitate during slow cooling which would also reduce corrosion resistance. This can happen with the relatively common gas quenches that are used in large vacuum furnaces by many knife manufacturers. I covered this in a previous article/video about custom vs production heat treating.

Cryo and Cold Processing

You will notice that the Vanax hardness dropped at 2025°F while the Elmax hardness increased all the way up to 2150°F. These heat treatments included a cryo step in liquid nitrogen after the quench. If cryo had not been used the Vanax would have seen a drop below 2025°F and the maximum hardness would not have been as high. The Elmax likely also would have seen a hardness drop in this tested range. As an example, the following chart shows AEB-L steel when quenched to room temperature vs placed in a freezer or in liquid nitrogen:

AEB-L steel vs austenitizing temperature

The AEB-L achieved its peak hardness around 1975-2000°F just like the Vanax and then dropped in hardness with further increases in austenitizing temperature. It reached a max hardness of around 64 Rc, though when no cold treatment was used it maxed out around 62 Rc. The reason for the drop in hardness above a certain temperature is because of retained austenite. In other words, the martensite finish temperature was below room temperature. Using liquid nitrogen after the quench means cooling the steel to a lower temperature getting closer to martensite finish. However, some retained austenite will stabilize and not be transformed even with the very low temperatures of liquid nitrogen, which is why the hardness still drops with an austenitizing temperature that is too high.

So the use of cryo can allow both higher hardness and corrosion resistance if the austenitizing temperature is increased. For a fixed austenitizing temperature, typically there is a 1-2 Rc increase but the corrosion resistance would not be affected.

Tempering

After quenching, steel is tempered to improve its toughness. The tradeoff is that hardness is also reduced through tempering. Below shows a tempering chart for MagnaCut with different austenitizing temperatures.

Different austenitizing-tempering combinations can be used to achieve the same level of hardness. For example, to achieve ~60 Rc, you could use 1950°F and 300°F, 2000°F and 400°F, or 2100°F and 500°F. Because the higher austenitizing temperature potentially means more chromium in solution we would expect the 2100°F and 500°F combination to achieve the best corrosion resistance for that hardness. A unique aspect of MagnaCut is that all of its chromium carbide is dissolved around 2050°F, as shown in the chart below. So if instead we were heat treating to ~63 Rc, 2050°F and 300°F, 2150°F and 400°F, and 2200°F and 450°F would all have approximately equal corrosion resistance. So austenitizing above 2050°F still leads to an increase in hardness for a fixed tempering temperature but the corrosion resistance would be unaffected.

There is an important aspect to tempering and corrosion when it comes to a different regime of tempering, however. Stainless steels and other high alloy steels see a bump in hardness by tempering above about 750°F, as shown in the following chart for Elmax:

You can see that the hardness sees a peak with tempering around 500°C (930°F). This increase in hardness comes from precipitation of small chromium, molybdenum, tungsten, and vanadium carbides. Because chromium is coming out of solution as a chromium carbide this “secondary hardening” also leads to a decrease in corrosion resistance. Below shows Vanax steel that I tested with a 1% saltwater spray test for 24 hours where one was tempered at 400°F and the other was tempered at 1000°F. The 400°F temper Vanax showed no corrosion while the 1000°F temper led to significant rusting.

Vanax tempered at 400°F (left) or 1000°F (right) before a 1% saltwater spray test

It is relatively common for knifemakers and knife manufacturers to temper at 950-1000°F. They do this for several reasons, though the main one is that the higher tempering temperature means the steel is less sensitive to overheating. This allows them to apply certain coatings to steel (that require higher temperatures to apply than a typical “low” temper of 400°F). It also means they don’t have to be as careful with grinding because the steel can be heated up much higher before approaching the tempering temperature (where the steel would soften).

The high tempering temperature can be used with many stainless steels to achieve similar levels of hardness as the low tempering temperature. In other words, you can have two knives at 60 Rc, 62 Rc, etc. with very different corrosion resistance depending on whether they tempered in the low range or the high range.

Hardness vs Corrosion Resistance for Different Steels

So after all of that we can return to our discussion of what makes one steel more corrosion resistant than another. Below shows Vanax and Elmax after a 1% saltwater spray test for 72 hours:

The Elmax rusted while the Vanax did not. Both were austenitized at 1975°F which is the recommended temperature for both steels according to their datasheets, and both were given a temper in the low range (400°F). As shown in the earlier chart, the difference in corrosion behavior is primarily due to higher chromium in solution for Vanax, which would roughly be 11.5% for Elmax and 14.5% for Vanax. As seen in the hardness chart, Vanax would actually be a bit harder than Elmax for this identical heat treatment. However, Elmax can be austenitized at higher temperature and achieve significantly higher hardness than Vanax which reaches its maximum around 61 Rc. The reason is because chromium also reduces martensite start and finish temperatures. Vanax has more chromium in solution for a given carbon/nitrogen in solution:

This means that for a given austenitizing temperature, Ms and Mf are lower in Vanax than in Elmax. So as seen below with an austenitizing temperature of 2025°F, the Ms was about 150°C. The Mf is sufficiently low that even with liquid nitrogen not all of the austenite is transforming to martensite, and thus hardness was lower with 2025 than 2000°F. Elmax, however, still has a predicted Ms above 150°C all the way to 2200°F, which is why its hardness increased all the way to 2150°F (the highest temperature I tried).

Thus an approximate relationship is created when comparing different steels to each other for their maximum hardness vs their corrosion resistance:

This trendline is usually correlated with chromium in solution. For example, Vanax and LC200N have >14% chromium in solution, which gives them a very high corrosion rating but also limits their potential hardness. On the other end of the spectrum is ZDP-189, which achieves very high hardness and is advertised as a stainless steel, but I discovered a few years ago that it is not, in fact, stainless. I measured only 8.6% chromium in solution with ZDP-189, which is quite low. D2, for example, I measured at 7.7% with a relatively conventional heat treatment, which is famously called a “semi-stainless” steel.

There are other complicating parts to this trendline, however. It does not always perfectly correlate with chromium in solution. Molybdenum, for example, is an element known to improve pitting resistance and to strengthen the chromium oxide passive film. In tests I did with 1% saltwater there was an improvement in corrosion resistance for a given chromium in solution if the Mo was increased:

CPM-154 with its high molybdenum content (4%) had acceptable corrosion resistance even with only 9.5% chromium in solution. (Note: the “corrosion ratings” in this chart are a rating of how much the samples rusted and not the same as the “corrosion rating” in the hardness trend plot which are from my knife steel ratings).

You may have also noticed that S90V, S125V, M390, and S110V are all above the hardness-corrosion resistance trendline. In other words, they have unexpectedly high maximum hardness for their corrosion rating. These steels all have a very high volume of carbide (>20%). Carbides are very hard particles and when the volume of them is reaching these high levels it can affect the bulk hardness that is measured. You can see that for the following two charts comparing non-stainless tool steels with different amounts of carbide (Vanadis 4 Extra, 10V, and 15V):

So while M390 and 14C28N both have similar Cr in solution (depending on austenitizing temperature), the M390 reaches higher hardness because it has so much more carbide:

M390 has a lot of carbide

14C28N not much carbide

The other steel above the trendline for hardness-corrosion resistance is MagnaCut. It does not have particularly high carbide volume, about the same as Vanadis 4 Extra:

MagnaCut also does not have particularly high chromium in solution, around 11%. Instead, MagnaCut has superior corrosion resistance to those other steels because all of its chromium carbides are dissolved in heat treatment. With typical stainless steels they have many chromium carbides, and the chromium in solution is lower around each carbide:

Thus the chromium carbides act as corrosion initiation sites. This is somewhat similar to the phenomena called “sensitization” in low carbon stainless steels that are cooled too slowly.

Image from [2]

Instead, all of the carbides in MagnaCut are vanadium or niobium carbides (after heat treating). Therefore those corrosion initiation sites are missing and so it has superior corrosion resistance for a given level of chromium in solution.

Comparing Steels vs Comparing Heat Treatments

Perhaps it is the above discussion that confuses some people, and they mix the low potential hardness of Vanax and LC200N with heat treating of other steels and assume that lower hardness means better corrosion resistance. However, as I have discussed, hardness and corrosion resistance don’t really correlate for an individual steel. If anything, higher hardness sometimes correlates with higher corrosion resistance. If you use higher austenitizing temperatures in combination with a fast quench and cryo, and temper at a low temperature, you get maximum corrosion resistance. That is also a recipe for high hardness (as long as the austenitizing temperature isn’t too high). However, tempering can be increased without detriment to corrosion resistance to heat treat to lower hardness levels (as long as the >750°F range is avoided).

Summary and Conclusions

Austenitizing temperature, quench rate, and tempering can all affect corrosion resistance. Austenitizing higher leads to both higher hardness and better corrosion resistance. Beyond a certain temperature cryo is necessary to get higher hardness, and even then there is a temperature beyond which hardness decreases. Quenching too slowly, as happens often in industry, can lead to a reduction in corrosion resistance. Tempering in the high temperature range (>750°F), also relatively common, significantly reduces corrosion resistance. Combinations of heat treating variables can be used to achieve a range of hardness values while maintaining high corrosion resistance. In other words, hardness does not correlate with corrosion resistance for a given steel. However, when comparing different steels to each other, there is a trend where more corrosion resistant steels typically have a lower maximum hardness. Molybdenum alloying, avoiding chromium carbides (such as in MagnaCut), and having a high volume of carbide all lead to higher potential hardness for a given level of corrosion resistance when comparing different steels to each other.

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[1] Binder, W. O., and C. M. Brown. “Atmospheric Corrosion Tests on High-Chromium Steels.” In Proceedings of ASTM, vol. 46, pp. 593-606. 1946.

[2] https://newzelindustries.com/what-is-sensitization-in-austenitic-stainless-steel/

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