Effect of Process Parameters on the Metallurgical Properties of a Boron-Added Cast Austenitic Steel Designed for Special Purposes

Abstract

A new kind of boron-added cast austenitic steel which also contained chromium, molybdenum and manganese was manufactured via vacuum induction melting followed by casting procedure. Solution annealing heat treatment was performed at three different temperatures for three different times to dissolve eutectic M2C carbides in austenitic matrix. All of the samples were rapid-cooled in oil medium after the solution annealing heat treatment. Aging treatments were carried out after solution annealing heat treatment performed at 1250 °C for 24 hours. Hardness value was decreased after solution annealing performed at 1250 °C for 24 hours. Transformation of M2C carbide with a hexagonal lattice into Fe-rich M6C carbide with a face-centered cubic lattice and formation of precipitates occurred as a result of aging performed at 700 and 800 °C. Sub-micron sized Cr23C6 carbides and Mo2BC precipitates were formed and hardness value was increased after aging performed at 700 °C. Nano-sized Cr23C6 carbides, Mo2B borides and Cr7BC4 precipitates were formed and hardness value was higher after aging performed at 800 °C. An optical light microscope was utilized to characterize solution annealing treatments and to perform grain size measurements. A scanning electron microscope was used to identify carbide types and carbide transformation during aging.