1095 Carbon/420 Stainless

[Dawes]

I've got a question which is along the lines of trivia, but maybe someone can provide some input:

The military's M9 bayonet is made from 420 Stainless, while the older M7 bayonet is 1095 Carbon steel. What are the relative merits of each in this particular application, and would one be superior to the other as far as toughness, edge-holding, etc.?

 

[unclesyd]

Being they are entirely two different steels it's probably a matter of design as the M-7 was a bayonet and the M-9 was bayonet and working knife. 420 SS is far better knife material than 1095 CS as it will be a better edge holder for the same ductility, due to it's higher corrosion resistance. 420 SS was at one time the standard for a high quality SS knife as it was readily available and easy to heat treat. 410 SS was the cheap SS knife and 420 SS was the top shelf material. It also maybe that about the time the M-7 was put into production there was a shortage of Cr and 1095 CS was the next best thing.

The 1095 CS is a plain high carbon steel that will hold a nice edge and will rust readily.
The 420 SS is a martensitic stainless steel high carbon and also high chrome. It is considered a SS steel though it will rust if not taken care of properly, but would be an order of magnitude better than 1095 CS in respect to rusting or corrosion from cutting different materials.

Both steels in their hardest state are somewhat britte and have to be heat treated in way to increase ductility I would think a requirement for a bayonet
There were also several surface treatments given to both materials to improve their corrosion resistance.

Here is link that I got from my brother as he has several bayonets in his collection.

http://www.usbayonet.com

 

[SMF1964]

I would disagree with the 420 stainless holding an edge better. However, the 420 is stainless and so won't rust and look ugly. I have a 1095 carbon steel carving knife that, to my knowledge, has not been sharpened in 30 years, but is covered with a tight patina of red/black oxide and so looks unsightly but still slices tomatoes like a 'ginsu'.

 

[EdStainless]

The 420 will not be as hard as the 1095, but since both would be used in a tempered condition there probably isn't a lot of difference.
Good knife blades are 440C. More Cr and C. Harder, tougher and more corrosion resistant. They still can't be honed as sharp as a 1095 razor. But they sure hold up in service a lot better.

= = = = = = = = = = = = = = = = = = = =
Corrosion never sleeps, but it can be slowed down.

 

[funnelguy]

440 lacks toughness as compared to 420. I would think toughness would trump edge holding abilities on a bayonet. Heaven forbid the thing would break in service! I'd want something that would bend before it would break. Then start to talk to me about hardness and the rest!