Effect of different surface treatments on the precipitation of boron nitride for stainless steel SUS304

This paper aims at finding the most proper surface treatment method to obtain the extreme low outgassing from boron nitride (BN) precipitated stainless steel. A correlation between surface treatments and precipitation aspects of hexagonal boron nitride (h-BN) on an austenitic stainless steel was studied. Precipitation aspects of BN on a polished surface with different method were observed using scanning electron microscopy (SEM). Surface treatments such as buff polishing (BP), electro polishing (EP), electrochemical buffing (ECB) and float polishing (FP) were employed. It was found that electron channeling pattern (ECP) showed no evidence of formation of the modified layer near the surface of both FP and EP treatments. On these surfaces, BN was precipitated almost uniformly and covered the whole surface, while BN precipitated not uniformly but spotty on the other surfaces (BP and ECB). As the thickness of the BN layer increased, strong oriented triangular crystalline BN was observed on the FP surface. The float polishing may be a candidate of the most proper surface treatment for BN precipitation.