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Effects of shot peen on stainless steel knife blade material

2004

I am looking for a source to find the effects of shot peening stainless steel, specifically stamped and forged knife blade material. The material would normally be Rockwell hardness 54-58. There are a couple of tradeoff's currently that must be made when using stainless steel as a knife blade material compared to high carbon steel. One of them is the fact that stainless does not retian an edge as well as the high carbon. Of course that is outweighed for the average user by the fact that it does not corrode easily and does not impart a "off" taste on the food it is being used to cut.

I am wondering if shot peening the metal would:

a)Increase the surface hardness of the metal, resulting in better edge retention (I have a feeling that the answer here will be "no" if my initial research is accurate in stating that shot peen only affects hardness to a depth of .005 - .010).
b)Improve the strength of the blade (reduce flexability).
c)How would it affect (or would it affect) the corrosion resistance of the metal (could you use less chromium in the metal and still maintian a high level of corrosion resisance)?
d)Would it reduce the tendancy of food that is being sliced to stick to the side of the blade by creating a slightly irregular surface vs. the standart polished surface.

Any help you could give me would be greatly appreciate.

Thank you for your time. Eric Rose President, AAA Sharper Edge

Eric Rose
AAA Sharper Edge - Duvall, Washington, USA

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As I've done a few knives in my time I have to say that if a knife is NOT stainless it does not always impart that off taste to foods, this is done by giving and maintaining a mirror finish on the steel. Now as I assume that you are in commercial production, I assume that you are aware of basic nomenclature of steel.

First off, try using 440 stainless, good edge, doesn't rust easily unless in hi temp or hi corrosion environments. Can't do 440? Use a faux damascus process, weld some O1 or other high carbon steel between two stainless billets, the cutting edge only needs to be about 1 mm thick.

In addition in order to keep things from sticking to the blade you might want to consider a hollow grind to the face of the blade (a shallow concave curve) Conversely you may want to attempt the opposite with a convex grind (the face standing slightly proud of the edge). The reason you have things sticking to the blade is that you have a very flat surface that isn't allowing air to get between the object and the face of the blade (making it stick via suction).

Now if you are using high carbon steel you may want to keep aware that shotpeening the blade may introduce microfractures in the steel which will weaken the blade. This is the core reason that most high and mid carbon steels need to be worked at least at a red heat. Another thought for you is how the blades are tempered, were they hardened first? (Quick and dirty on hardening, heat to critical heat; i.e. just before the steel turns molten, commonly a bright yellow that borders on incandescent white. Then quench in brine or oil, if you are looking to harden the blade a LOT use brine, my brine mixture is common table salt dissolved into water until a potato floats in it, you will need about 4 gal for a reasonable sized blade.)

Then there is tempering, which is done after hardening, since once again you are working on getting a good hard edge I suggest using sandpaper or a file to get a good shiny spot on the entire edge, heat the edge up note the colors that come out here, you are after a hard cutting edge so I suggest a dark purple, straw will be too hard. Once again, used the above mentioned brine quench.

Well my long winded explation is over, I hope that this will help you out and give you some ideas. If you need any other help beyond this in relation to blades, let me know.

Marc Banks
- Elizabeth City, North Carolina
2004