"Blue" Stainless Steel.....

[NickE]

I'll start by saying this is not my idea. Our customer is having trouble identifing btw two parts. They wondered if we could blue the one made of stainless steel (7C27Mo2:SAE420).

The problem is that we dont want to lose the temper on this material since the high hardness (~535HV) is important along with the high strength for fatigue.

Can anyone suggest an (atmosphere, temperature, quenchant) that can solve our problem. I know I can blue the steel, I just think that 6-800F will temper it out.

thanks
nick

 

[Christian62]

Hmm,
I looked for SAE420! I must have the wrong book! Maby ASTM 420 ?
But 7C27Mo2 is a martensite Stainless Chromium Steel.
So Annealing is around 1500°F to 1600°F and Process anneal is from 1200°F to 1400°F. But close to 800 I would wory about Carbides (precipitation from 900°F to 1700°F) that would realy fragilise your Mart SS. Also there is a rapide decline in mechanical properties passed 900°F.
What type of material does he have to I.D. ? Maby we can find something smart!
Good luck

 

[TEV]

Try a hot permanganate solution. I think this will blacken your stainless. If you want blue, try adjusting temperature and/or concentration.

 

[smcadman]

I can't tell you where to begin your search, but a few years ago we had to special order from Germany some black 18 gauge stainless steel (we were in Dallas, TX). It was expensive to begin with, but we had to have it polished to a #8 (mirror) finish. It looked like a mirror with a window-tint treatment.

Flores

 

[NickE]

About the 420: dont trust the suppliers paperwork....


Any way thanks guys.

This is a flexing Valve application There is not a chance of changing materials. I cannot etch/mark the surface in any way. (Fatigue)

TEV-- Hot permagnate? do you mean potassium permagnate? Should I dissolve it in water or do I need to melt a solid compound? 90-120C higher? I dont really wnat to go above 300C....

nick

 

[TEV]

Nick:

Yes, potassium permanganate dissolved in water, try 50C. This is a strong oxidizing solution.

 

[NickE]

Ahh Thanks TEV Ill suggest that the next meeting.

nick

 

[Celebur]

SAE/AISI Type 420 is actually a commonly used grade of martensitic stainless steel. Of course, now there will be a UNS number to replace it.