K390 vs VG10 Steel

VG10 was developed in Japan by Takefu Special Steel to be a versatile stainless steel, K390, on the other hand, was developed by Bohler as an ultra-wear resistant non-stainless steel.

The key difference between K390 and VG10 lies in their compositions – K390 is a high vanadium non-stainless tool steel, while VG10 is a stainless steel containing 15% chromium. 

K390 achieves its extremely high wear resistance through a very high 17% vanadium carbide content and powder metallurgy production for fine carbides.

In contrast, VG10 relies on chromium carbides and contains 1.5% cobalt to improve its performance at high-tempering temperatures.

K390 provides unmatched wear resistance but poor corrosion resistance, whereas VG10 offers significantly lower wear resistance but can be used in wet environments like kitchen knives. 

Their compositions, carbide types, and production methods result in very different properties and performance.

K390 vs VG10 Steel at A Glance

Hardness

K390 has significantly higher hardness and wear resistance compared to VG10. The hardness of K390 steel can reach up to 66HRC when properly heat treated, while VG10 tops out around 60 HRC. 

However, in knife applications, VG10 and K390 steels are often heat-treated to more modest hardness levels in the 58-62 HRC range.

K390 contains a very high volume of vanadium carbides, around 17%, which are extremely hard and provide excellent wear resistance.

This results in K390 having among the highest wear resistance of any non-stainless steel, matched only by steels like CPM-10V and Maxamet which have even higher volumes of vanadium carbides.

In contrast, VG10 stainless steel contains primarily chromium carbides and has an estimated carbide volume of around 12-16%.

The high vanadium carbide content and potential for greater hardness means K390 will have substantially better edge retention and resistance to abrasive wear compared to VG10.

However, the high hardness and large volume of carbides in K390 also make it more difficult to grind and polish.

Overall, K390 significantly outperforms VG10 in hardness, wear resistance, and edge retention due to its much higher content of extremely hard vanadium carbides.

Toughness

K390 demonstrates better toughness than VG10, making it more resistant to impacts and less prone to chipping or breaking when used for hard tasks. 

The fine-grained microstructure provides K390 with enhanced crack resistance compared to VG10. This makes K390 a better choice for rough-use knives where toughness is critical.

Testing shows that K390 steel has better toughness compared to VG10 steel, by about 15-20% on average. 

VG10 had an average toughness of 5.8 ft-lbs at 60 HRC, while K390 was tested at 62-63 HRC and found to have toughness comparable to steels like S35VN, CPM-154, and Vanax all better the toughness of VG10 steel.

The fine-grained microstructure of K390 from powder metallurgy production gives it an advantage in toughness over the coarser carbides in VG10. 

The toughness advantage means K390 can withstand more abuse and shock forces before chipping or breaking compared to VG10.

This is an important property for knives as it reduces the chance of damage if the blade is dropped or impacts a hard object.

While both steels have reasonably good toughness, K390 can match VG10’s toughness while also having vastly superior edge retention and wear resistance.

So for most cutting tasks, K390 steel provides better overall performance than VG10 steel thanks to its balance of properties.

Edge Retention

K390 steel has vastly superior edge retention and wear resistance compared to VG10 steel.

CATRA Testing shows K390 has extremely high slicing-edge retention, surpassed only by steels with even higher volumes of vanadium carbides like CPM-10V and CPM-15V. 

In contrast, VG10 contains primarily chromium carbides and has an estimated 12-16% total carbide content. VG10 has moderately good edge retention but is substantially below 440C in testing, whereas K390 is far above.

This is due to K390’s very high 17% vanadium carbide content. Vanadium carbides are extremely hard at around 3000 HV, which imparts excellent abrasion resistance.

The high hardness of K390 steel also contributes to increased wear resistance. The large volume of fine vanadium carbides in K390 prevents both microchipping and abrasive wear along the edge.

So K390 knives will maintain sharpness incredibly well under sustained cutting tasks better than VG10 knives.

Overall, K390 has vastly superior edge retention and wear resistance compared to VG10 due to its higher hardness and much greater volume of hard vanadium carbides.

For demanding cutting applications, K390 will significantly outperform VG10 in terms of maintaining a sharp edge.

Corrosion Resistance

VG10 steel has far superior corrosion resistance compared to K390 steel.

VG10 is a stainless steel containing 15% chromium, which enables it to form a protective chromium-oxide passivation layer to resist corrosion.

In contrast, K390 is a non-stainless tool steel that lacks sufficient chromium to provide corrosion resistance.

Testing ranks VG10 at around a 7 out of 10 for corrosion resistance, similar to 440C. This makes it suitable for most environments apart from highly corrosive ones.

 With only 4% chromium, K390 will readily corrode without proper care. It requires maintenance like oiling and coatings to prevent rusting.

While K390 offers tremendously better edge retention and wear resistance, its lack of corrosion resistance makes it unsuitable for applications where moisture or corroding environments will be encountered like in kitchens.

VG10 can be used in a much wider variety of conditions without corrosion concerns. So VG10 is far superior to K390 when corrosion resistance is a priority.

However, for purely dry-cutting applications, K390 steel wear resistance is unmatched by VG10 steel.

Ease of Sharpening

VG10 is significantly easier to sharpen and grind compared to K390. The primary reason is the types of carbides in each steel.

K390 steel contains a very high volume (17%) of vanadium carbides. Vanadium carbides have a hardness of around 3000 Vickers, which is much harder than common abrasives used for grinding and sharpening, like aluminum oxide.

This makes K390 very difficult to cut and abrade. VG10, on the other hand, contains primarily chromium carbides which are much softer at around 1700 Vickers.

VG10 also has a lower overall carbide content at 12-16%. The lack of hard vanadium carbides means VG10 can be ground and sharpened much more easily and quickly compared to K390.

The occasional large carbides in VG10 may cause some grinding issues, but overall VG10 is substantially easier to sharpen and grind than K390.

For those looking to frequently sharpen their knives, VG10 would be the better choice over the extremely wear-resistant K390.

Final Thoughts on K390 vs VG10 steel

In reviewing the properties of these two knife steels, it’s clear that VG10 and K390 have very different strengths based on their origins and compositions.

VG10 steel with 15% chromium content provides decent corrosion resistance, making it a great choice for kitchen knives and EDC blades that see frequent exposure to moisture. 

While its edge retention lags behind some other powder metallurgy steels, VG10 strikes a good balance of properties for all-around stainless steel.

On the other hand,  K390 is a non-stainless steel with 17% vanadium carbides, K390 achieves some of the highest hardness and edge retention of any steel, surpassed only by other vanadium-rich alloys like CPM-10V.

K390 steel powder metallurgy production gives it enhanced toughness over conventional steel with the same hardness.

While it falls short of VG10 steel in corrosion resistance, K390 steel excels in edge retention/wear resistance.

For pure cutting performance, I prefer K390 due to its superior edge retention and toughness. With careful maintenance, K390 can make an excellent steel for hard-use blades where corrosion is not a major concern.

For EDC tasks, VG10 may be the safer choice, but for pure cutting ability, K390 is hard to beat.

Both blade steels have seen extensive use in knives by top companies like Spyderco, showing their ability to satisfy diverse users. 

But between the two, K390 knife steel stands out if your main priority is getting the most cutting mileage out of your blade steel.