[heattreater]

Can anyone tell me if a piece of 440C will pass a surface contamination test if it is stress relieved in air prior to hardening in vacuum?

(the test would have to be done after the vacuum hardening of course)

[DrOrpheus]

What temperature are you stress relieving it at?

[heattreater]

1250F in air.

[DrOrpheus]

Can you hold it at 1250 in the vacuum, then raise it up to the high heat for hardening? I am not an expert on 440C, but I'd venture to guess it'd be ok and pass the surface lab at 1250 in air. You may get some scale, but things don't start happening at that low of a temperature generally. Although, I'm more familiar with alloy steels and the temperatures at which they like to take on or lose carbon.