Replacing 17-4PH with Cold Drawn Nitronic 60? 2

[RayBen]

I've been looking into a galling problem, and had some questions about Nitronic 60. The situation is two parts made of 17-4PH, H1025 condition, are in a high vibration environment, sliding tangentially against one another, and at worse case, can see a healthy amount of bearing pressure (30 ksi or so). They are cold welding themselves together. One of the parts has a Nibron coating, but it doesn't seem to be doing the trick. It seems to wear off quickly. Lubrication can't be used in this application.

I was thinking of trying to change the coated part (the only one I can change) to Nitronic 60, but in it's annealed state, it's considerably weaker then the 17-4PH it would be replacing. When cold drawn 30-40%, Nitronic 60's Ultimate and Yield Strengths are in the right ball park, and the hardness is similar to 17-4PH as well, which seemed promising. Are Nitronic 60's good galling and wear properties affected by cold drawing it? I haven't been able to find much info about it in it's non-annealed state.

Thanks for any help.

 

[rorschach]

If anything, the galling properties improve, but please remember that CD bar has a strength gradient and is softer/weaker in the core than on the outer surface. For small bars this isn't much of an issue, but when you get to the biggest size that bar is available in (2-1/2" o.d. is the biggest I've ever been able to find), there can be an appreciable gradient. It's corrosion properties go down with cold-work too. It is not NACE MR0175 qualified if that is an issue.

 

[unclesyd]

Using Nitronic 60 @ Rb 95

N60 vs 17/4 (Rc43) wear is 5.4 mg/1000 cycles
N60 vs 17/4 (Rc32) wear is 4.9 mg/1000 cycles

Using Nitronic 60 HS @ Rc 29

N60 HS vs 17/4 (Rc43) wear is 3.7 mg/1000 cycles

Galling (Threshold Galling Stress)
N60 vs 17/4 (Rc34) 50
N60 HS vs 17/4 (Rc43) 47+
N60 HS vs 17/4 (Rc34) 37

By The description of your problem you have several other variables in the equation, speed and the amount of time the additonal pressure is applied and how fast is it applied.