Surface precipitation of boron nitride on the surface of type 304 stainless steels doped with nitrogen, boron, and cerium

The surface compositions of two types of stainless steels in vacuum were observed with AES and XPS at 1000–1100 K; a 304 stainless steel doped with nitrogen and boron (304-NB) and a 304 stainless steel doped with nitrogen, boron, and cerium (304-NBCe). The changes of surface compositions of these steels were compared with that of commercial 304 stainless steel. A thin layer of boron nitride came out from grain boundaries and spread over the surface of the 304-NB, but did not uniformly cover the surface. The spreading mechanism of the boron nitride layer at the initial stage of heating can be explained by Avrami’s model. In the case of 304-NBCe, a boron nitride layer almost uniformly covered the surface at the early stage of heating, and rendered the surface inert to the adsorption of carbon and oxygen. Therefore, the 304-NBCe stainless steel is a candidate material for vacuum vessels.