Lowering of Liquid-phase Sintering Temperature and Improvement of Some Properties of P/M SUS304L Stainless Steels by the Addition of Silicon and Boron

摘要

The addition of silicon (Si) and boron (B) to SUS304L stailess steel powders has been examined, aiming at towering the liquid-phase sintering temperature, and at improving the mechanical properties and corrosion resistance. Addition of Si resulted in the duplex structures of austenite (#gamma#) and ferrite (#alpha#), which gained the strength due to the crystallization of #alpha# phase. By the over addition of Si, the ductility was lowerd. Addition of B improved the ductility, which was due to the precipitation of fine borides around the grain boundaries. These precipitation formed the spherical pore. By the simultaneous addition of both elements, the sintering temperature was lowerd to 1500K, which was lower than that of single element addition by 100 approx 150K The specimens showed an improved mechanical properties such as 595MPa in tensile strength and 36.7 percent in elongation. The corrosion resistance by intergranular corrosion test of a boiling solution of 65 percent HNO_3 was not improved by the addition of Si and B. This may be due to low sintering density and the existance of many pore defect.