Does 17-7PH steel needs further heat treatment to ensure min. of 92 HRB? 2

[rollingcloud]

I am new to heat treatment. I am updating material properties requirement of a bearing race made of 17-7PH per AMS 5528, which is already solution heat treated per spec, however, I cannot find a min. hardness for the metal, it only has a max hardness requirement of 92 HRB. I am not sure if precipitation heat treat is needed since the hardness will be at least 34HRC which is significantly higher than the approx. target of 92 HRB. Would precipitation heat treat make the metal difficult to work with? it's going to be basically a ring.

Also, is there a major upgrade to corrosion resistance of solution heat treated stainless steels by adding precipitation heat treatment? Any tips would be greatly appreciated!

 

[EdStainless]

Look up a 17-7PH spec sheet.
The HT is a two-step process.
The most common is first heat to 1400F x 90min and then cool to RT.
Keep at RT for at least 1/2 hr.
Heat to 1050 +/-10F for 90min.
This gives you the standard TH1050 condition and should give you upper-HRC30's (or even low 40's depending on chemistry).
You know that it changes size when aged right?
Most of the change (85% of it) happens in the 1400 step.
For precision applications many people will rough machine, HT at 1400F, finish machine, 1050 age.
In the 1400F (T condition) the hardness is only about 30-33 HRC so it is still easily machinable.
For lest precise applications people just factor in the 0.0045"/inch growth and go with that.

You never should use this alloy unless it has been conditioned and aged.
The general corrosion resistance doesn't change much, but the SCC resistance does.
At moderate stress levels (<75%) TH1050 material is highly resistant.
People get into trouble when using springs in a much higher strength condition (CH900) at high stress levels (>85%).

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P.E. Metallurgy, consulting work welcomed

 

[mfgenggear]

rolling cloud
eds data is good, just to add purchase AMS2759/3 precipitation hardening. wealth of info in there.

 

[rollingcloud]

Ed

Thank you for the details.
"You never should use this alloy unless it has been conditioned and aged.", by that you mean solution heat treated 17-7PH is not good enough? Is it because SCC resistance or more to it?
I realized I made a mistake, this 17-7PH is a shield of a spherical bearing, not a race, it's going to welded on the race to keep a seal in place, it does not experience any significant load.

 

[rollingcloud]

mfgenggear

Did not expect to see you here lol

 

[EdStainless]

If you can live with a max hardness of 90 HRB then use it annealed. That would work for shields.
If you need it any harder then TH1050 is really your only option.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, consulting work welcomed

 

[rollingcloud]

EdS

Thank you for the responses.
Happy holidays!