Summary for scratch resistant stainless Discussion
For a scratch-resistant stainless alloy, the thread points away from 304 and 316 and toward harder cutlery-grade stainless steels. Eric Mart asked whether he needed heat treatment or a different stainless alloy for a therapeutic, patent-approved tool made from 1/4-inch plate, since 304 and 316 still showed surface scratches after polishing. Ray Kremer said that when he thinks of scratch resistance, he thinks of 420 and 440C, noting that knives are made from these grades and suggesting Eric test a stainless knife for suitability. He added that these steels would need heat treatment after machining or forming to achieve hardening. By contrast, he said 304 and similar grades cannot be hardened by heat treatment, except by nitriding, which sacrifices corrosion resistance. He also mentioned Kolsterising as a possible alternative process that might work.
Q. I’m researching for the proper stainless Alloy to use on A Therapeutic Patent- approved Tool that is resistant to scratches. I have tried 304 & 316 plate to polish, It continues to have surface scratches. Do I need to take the next step & have the Tool Heat treated or a separate stainless alloy application? 1/4″ plate Is Needed….
Thanks For Your Interest
Erik
Eric Mart
Patent approval on therapeutic massage tool – Davenport, Iowa
May 16, 2012
A. Hi Eric!
When I think scratch resistance, I think of the cutlery grade stainless steels like 420 and 440C. Knives are made from them, so get a stainless knife and see if it is sufficiently scratch resistant for your purposes. It will need to be heat treated for hardening, after you’ve machined or formed it into your part.
The stainlesss steels you mentioned, 304 etc, can’t be hardened by heat treatment. Except by nitriding, and then you lose your corrosion resistance. Or maybe by Bodycote’s Kolsterising process, which sounds like it might work for you.
Good luck!
Lee Gearhart
metallurgist – E. Aurora, New York
A. Erik,
I don’t really get into alloy selection too much, my customers generally already know what they are using before they come to me, but I do know that the 400 grades are used far more than the 300 grades for things that require material hardness, for instance a surgical blade that must retain its cutting edge for as long as possible. I suggest you do an internet search on “stainless steel hardness”.
Ray Kremer
Stellar Solutions, Inc.
McHenry, Illinois
