440C tempering question

[dparndt]

I have a 440C part that is tempered at 400 F to a Rockwell C hardness of 58-60. I am looking into a coating process that needs to be done at 428 F. Will being at that temperature reduce the hardness or change any of its other properties significantly?

 

[Metalguy]

You should be right ~Rc58 after some time at 428F, according to my old Carpenter SS book. Watch out for decarb.

"You see, wire telegraph is like a very long cat. You pull his tail in New York and his head is meowing in Los Angeles. Do you understand this? Radio operates the same way: You send signals here, they receive them there. The only difference is there is no cat." A. Einstein

 

[dparndt]

Thank you!

 

[TemperedMartensite]

Decarb at 428F?

 

[Metalguy]

Hardly. But I've heat treated a lot of 440C, and if the austenitizing furnace atmosphere is the least bit oxidizing or not reducing enough, it will decarb.

"You see, wire telegraph is like a very long cat. You pull his tail in New York and his head is meowing in Los Angeles. Do you understand this? Radio operates the same way: You send signals here, they receive them there. The only difference is there is no cat." A. Einstein