Papers by Keyword: MC Carbide

Abstract: A matrix type high speed steel YXR3 designed for a combination of wear resistance and toughness is investigated for its mechanical properties after hardening by deep cryogenic treatment follow by tempering. The deep cryogenic quenching carried out at -200 °C for 36 hours and the single step tempering results in an obvious improvement in wear resistance while balancing the toughness, comparing with the conventional quenching followed by a double tempering treatment. The quantitative image analysis reveals little difference in the MC carbide size distribution between tempering at different temperatures. The synchrotron high energy XRD confirms the MC type carbide with some evolution in its orientation together with tempered martensite approaching the BCC structure at higher temperatures. In contrary to the conventional quenching and tempering, the lowest tempering temperature at 200 °C yields a moderate drop in hardness with increase in surface toughness proportionally while exhibiting exceptional wear resistance. Such thermal cycle can be recommended for the industry both for the practicality and improved tool life.

Abstract: The microstructure and chemical composition of MC carbides in the modified variants of AISI M2 type high-speed steel after casting, annealing, carburising and subsequent final heat treatment (quenching and tempering) have been studied by focusing on diffusion processes in these carbides and their stability during high-temperature treatments. Significant changes in both the microstructure and chemical composition of the MC carbides as well as in their volume fraction shown to occur in the high-speed steels studied were attributed to decomposition, coagulation and dissolution of these carbides during heat treatments caused by strong diffusion of alloying elements and carbon. It was also shown that boron, in general, strongly suppressed the diffusion of carbon during carburising.