INFLUENCE OF TEMPERING TEMPERATURE ON STRUCTURE AND HARDNESS OF 29% Cr WHITE CAST IRON APPLICATION FOR MAKING SCREW SHAFT IN BRICK EXTRUSION MACHINE

Abstract

High-chromium white cast iron possesses excellent wear and corrosion resistance. To achieve these properties, the cast iron is typically quenched and then tempered at various temperatures to modify the density and size of the secondary carbide particles precipitated during the tempering process. In this study, high-chromium white cast iron containing 29% Cr, after being quenched at 950 °C, was tempered at temperatures ranging from 200 °C to 500 °C. Optical microscopy, X-ray diffraction, and scanning electron microscopy were used to observe and evaluate the precipitation of carbide particles in the resulting microstructure. A hardness tester was also employed to assess the changes in hardness. The results indicate that tempering temperature affects the precipitation of secondary carbide particles, thereby altering the hardness of the cast iron. Within the tempering temperature range of 200 °C to 500 °C, an increase in temperature tends to result in higher hardness. This study also contributes to a better understanding of the influence of secondary carbide density on the hardness of 29%Cr white cast iron during the tempering process.