I am designing a couple of linear actuators for the aerospace industry with PH steel rods. I will be requiring chrome plate on each for improved wear resistance. My shotpeening experience is paltry, so I want to make sure I am stipulating requirements correctly/appropriately. The materials and heat treats for each rod are as follows:
Rod #1: PH13-8Mo, H1000 (43-47 HRC)
Rod #2: 15-5PH, H1025 (34-42 HRC)
For each, I envision the following process:
1. After grinding OD, stress relieve at 375F for 3 hours
2. Shotpeen per AMS-S-13165 using ceramic bead, .006-.010A (PH13-8Mo) .012-.016A (15-5PH), 100% coverage required.
3. Chrome plate per AMS-QQ-S-320, Class 2, Type I, .003-.006 inch thick.
4. Hydrogen Embrittlement Relieve at 375F for 8 hours (13-8) 3 hours (15-5) (per AMS-QQ-C-320)
5. Final grind
6. Stress Relieve at 375F for 1 hour.
Question #1
Is the shot peen callout above sufficient or is it recommended that I callout a specific bead size?
Question #2
Since PH13-8Mo, H1000 is >200ksi UTS and >.375 in diameter, I chose .006-.010A. Since 15-5PH, H1025 has a UTS of 155ksi and >.375 diameter, I chose .012-.016A. Both intensities are per Table IV of AMS-S-13165. Is this appropriate?
Question #3
Where in AMS-S-13165 is "% coverage" addressed (if at all)? I have used this terminology in the past, but only because I learned from others. I don't see any references to >100% coverage. What is the reason for requiring >100% coverage? What does it even mean? And how does it help/hurt?
Question #4
Do any of the stress relief bakes have an adverse effect on the shotpeen (i.e. roll back the residual stress)? I believe that 375 is a safe temperature for PH steels, but I want to be sure...
Question #5
Is AMS-S-13165 the appropriate spec to use? What's the difference between it and AMS2430, which I am not familiar with?
Thanks for all your help!
Mike Boland
