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The effect of austempering on the microstructure and mechanical properties of PM Fe-0.8c steel aloyed with copper and nickel
(Carl Hanser Verlag, 2019) Gokmese, Hakan; Saricicek, Nurullah; Gural, Ahmet
The effects of austempering heat treatment on the microstructure and mechanical properties of sintered steel containing 3 % Cu and 3 % Ni powders with addition of 0.8 % graphite powders were examined. For this purpose, the powder mixtures containing 3 % Cu, 3 % Ni, and 0.8% graphite powder were compacted under 700 MPa of pressure within molds in accordance with the standard tensile and impact test specimen dimensions. All of the green compacts were sintered under an argon (99.99 %) gas atmosphere for 20 min at 1 150 degrees C. The austempering heat treatments were applied to the sintered specimens for different periods ranging from 15 to 120 min in a salt bath at 350 degrees C in order to obtain a bainitic structure after the austenitization process at 850 degrees C. The hardness, tensile, and charpy impact tests were carried out at room temperature. It was found that there was a decrease in the hardness value depending on the austempering conditions; moreover, a significant increase was observed in the tensile and impact toughness values. Remarkable strength and ductility values were obtained with the austempering applied for 60-120 min.