Q: I am currently using 18-8 stainless steel socket head cap screws coated with MoS2 in a vacuum. I am having problems with the screws clamping force is sometimes loosening and they sometimes gall and jam, due to elevated temperature (700° to 1000° C) and heat cycling. What would be the most cost-effective screw option that will be less susceptible to these problems?
A. Yes, coating a 18-8 stainless screw with MoS2 will not really help. The stainless steel screw will stretch or creep at those temperatures and that is what you are seeing. The best option will be an Inconel 600 bolt as it will not be susceptible to creep at those temperatures and will also be a cost effective solution. Another solution to consider may be Molybdenum screws if you are in a vacuum with no oxygen.