moly disulfide coating on 15-7 stainless steel

[idesign73]

I was wondering if anyone could give their opinion on a problem I have. My company uses Belleville washers(15-7 stainless steel)in liquid level gauges for steam/water applications. We have encountered a problem where the Belleville washers are cracking during operation, causing gauge failure. We have begun to gather data from the vendor, however, I am wondering if the moly disulfide coating used for lubrication (applied per MIL-16232) could be causing the washers to become brittle and crack (my main method of thinking is that the sulfur could be causing brittleness in the material). According to the vendor they don't think this is a problem but I was wondering if anyone out there would have another view on this. Thanks for any insight you can give. If you need further information, let me know and I will be as helpful as possible.

 

[phoward]

I do not know about the sulfur, but if you have any chlorine in the water at all, it will cause SS to crack. Other halogens could have a similar effect, you might check out the water conditioners for flourine, bromine, chlorine, iodine. The high temperatures could exacerbate the issue.