SUS304ステンレス鋼のほう化処理に及ぼす溶融塩浴中のB添加量の影響

Abstract

The steel material is used for various applications, and there are a lot of parts to which wear resistance is required. For instance, steel is used in gears and turbine braid exposed to high-speed fluid which contains fine particle. The austenitic stainless steel is excellent in corrosion resistance. However, because it is not possible to stiffen by quenching, the development of the method of improving abrasion resistance is required. Recently, boriding is seen as a solution. Boriding is divided roughly into molten salt bath method, powder-pack method, gas phase method, and electrolytic method. Among the method mentioned, molten salt bath method is the easiest technique which can be processed without special equipment. In this research, the influence of the B density in molten borax on the formation layer of SUS304 steel surface was examined. Boriding were performed in molten borax which contained 1~7 mass%B at 1200 K for 14.4 ks. As a result of the examination, the surface hardness becomes about 2200 HV when the density in molten borax is 2 mass%B or more. Also the wear resistance too has improved remarkably. Furthermore, it was understood that the formation layer on the surface was FeB, and, additionally, consisted of elements such as Fe, Cr, and B from the analysis of the X-ray diffraction measurement.