Determining failure temp from SS colouration 1

[IKBrunel]

We have a bearing failure and this has led to one adjacent component becoming coloured - straw colour with some blue hue.

Does anyone know the correlation of different stainless steel colours with temperature. I tried checking my annealing literature but could not find anything.

Thanks

 

[ssnh]

all the ones i have seen have been created by individuals - mine is...

photographs probably wouldn't do it justice.

 

[Fugeguy]

Below are some pictures for standard bearing steel.

You have raised an interesting question.

I will look into doing some tests on stainless bearings.

 

[NickE]

Stainless is going to show the same colors, but at much higher temperatures. To achive blue 600F is generally required. Straw is ~400-500.

This is in air in a furnace. Using martensitic 420ss spring strip.



Nick
I love materials science!

 

[Fugeguy]

I think Nick is correct.

Our stainless bearings primarily use SUS440C.

We are going to try and get some tests run but it will take awhile.

 

[IKBrunel]

I came across this page:

http://www.mcnallyinstitute.com/05-html/5-3.html

Giving the following statement:
"The metal will become discolored and soften as it anneals. Annealing can occur any time the temperature exceeds 300°F (150°C):
Straw yellow 600° F. 315° C.
Brown 700° F. 370° C.
Blue 800° F. 425° C.
Black 900° F. 480° C"

But it does not substantiate the information. Still hunting ... !

Many thanks for the responses so far, I'll keep watch.