Galling of 17-4 Plate

[kmpiatek]

I am having a problem with galling on a 17-4 stainless steel plate. The plate moves back and forth and will cycle in each direction once every 15-20 minutes. This plate is sandwiched between two seals(one each side) made from Nitronic 60. Is there a better material combination that I should use? (There is amonia in the atmosphere were this si used so aluminum and bronze are not an option) Is a coating a better route to take?

 

[AJohnson]

I think you should look at coatings and/or additional lubrication, as well as increasing the area of the plates to reduce the pressure. ASM's Metals handbook has a short table on threshold galling stress between various combinations of metals. The table shows that your combination of metals never galled during testing, at an applied pressure of 50 ksi. This leads me to think a) you have higher pressures and/or b) the amonia in the atmosphere is effecting the galling process. If the pressure and temperature are low, and it seems that the galling is being caused by the amonia atmosphere, possible solutions might be either a teflon coating on the 17-4 plate, or a sheet of UHMWPE between the Ni-60 and 17-4 PH. Andy