M390 is a durable steel with better corrosion resistance and toughness than K390, due to its higher chromium content and lower hardness. However, K390 is a harder steel with far better edge retention than M390. If you want an everyday knife that can handle abuse and infrequent care (besides sharpening), M390 is the best choice. For a very strong steel that retains an edge no matter whether you’re billeting wood or butchering while hunting, K390 is the superior choice.
What are the Differences Between M390 and K390 Steel?
M390 and K390 are steel alloys with very different compositions. While M390 is considered a stainless steel, K390 is a semi-stainless steel. The “stainless steel” classification means that M390 has a higher chromium content in the alloy. The chromium content in M390 is 20%. For K390, the chromium content is 4.25%. This contributes to K390 being a harder steel, but more prone to rust and discoloration than M390.
- M390 is a stainless steel.
- K390 is a semi-stainless steel.
- M390 has almost 5 times as much chromium in its alloy, compared to K390.
- K390 contains more than twice as much vanadium, compared to M390.
Because M390 steel has a higher chromium content, it has a lower vanadium content in the alloy. M390 contains 4% vanadium, while K390 contains 9% vanadium. Vanadium is added to steel alloys to increase the strength of the steel. The different alloy formulas of M390 and K390 result in very different performances, as we’ll cover in depth below.
Head-to-Head Comparison: M390 Vs. K390 Steel
If you’re trying to decide whether an M390 or K390 knife is the better choice, it’s essential to know the pros and cons of both steel alloys. We will cover all the important comparisons below, plus our recommendations based on how you wish to use your knife:
Stainless steel resists rust and discoloration better than other knife steels. So, M390 outperforms K390 when it comes to corrosion resistance. The high chromium content in M390 makes it a stainless steel that is extremely resistant to rust and discoloration. K390, on the other hand, is a semi-stainless steel. Because of its low chromium content, K390 is more likely to rust or discolor after use, or during storage.
The Rockwell hardness scale for K390 steel is 64–65 HRC. This puts K390 into an elite class of hard steels that resist scratching, deforming, and abrasion. In comparison, M390 has a hardness rating of 60–62. While a lower hardness steel is less likely to chip or crack, it also won’t be able to be honed to the razor edge capable of a harder steel. Elite knives used by top chefs and butchers have a hardness similar to K390, putting this steel in great company.
Although hardness measures the ability of a steel to resist scratching and deforming, toughness measures how well a steel resists fracturing and chipping. Typically, harder steels are less likely to deform, but more likely to fracture. This is the case with K390. Because K390 is such a hard steel, it is more likely to be chipped or fractured than M390. As a softer steel, M390 is more likely to bend, deform, or scratch than K390. This means that M390 is a tougher steel than K390, since it can withstand more punishment without breaking.
K390 is a big winner when it comes to achieving a sharper edge than M390. K390 also retains a razor-sharp edge longer than M390. The tradeoff is, K390 is a bit more challenging to sharpen than M390. If your priority is an extremely sharp knife that holds its edge through a grueling hunting or camping trip, K390 is the better choice. M390 simply can’t get as sharp as K390, and it needs more frequent sharpening to retain an edge.
Better for Hard Use
If you need the best possible blade for the job, choose K390 over M390. What you lose in corrosion resistance and toughness, you more than make up for by having a sharper blade that won’t dull halfway through butchering game or tackling campground tasks. As long as you properly clean and care for the blade, you’ll be able to avoid any serious corrosion that could impact blade performance.
Better for Everyday Use
If your priority is a knife that can take everyday abuse and exposure to the elements without corroding or cracking, M390 is the superior choice. M390’s corrosion resistance is excellent. So, you can carry a folding knife with an M390 blade to work in all weather without fear of rust or corrosion. You won’t get the same top-end performance from M390 steel that you will from K390, but you won’t have to worry about corrosion and chipping.
Is M390 Better Than K390 for Knives?
M390 and K390 steel are both high-quality choices for knife blades. If you’re torn between the two types of steel, keep these facts in mind:
- M390 is far better at resisting rust and corrosion than K390.
- K390 is a harder steel than M390, which means it can be honed to a sharper edge.
- M390 is tougher than K390, which means it will resist fracturing and chipping.
- K390 retains an edge longer than M390, so you’ll need to resharpen less often.
- If your priority is a knife that retains an ultra-sharp edge for tough work, K390 is better than M390.
- If you want a sturdy knife that won’t corrode or crack, choose M390 over K390.
The key to choosing between these two steel types depends on the work you need to do with the knife. Butchering fish, birds, and other game is a job for K390. If you are just going to be using your knife for general everyday tasks, M390 is superior.