Abstract
An X-ray diffraction line broadens considerably when steels transform into a martensitic structure on quenching. By using eight types of steels with carbon contents between 0.38 and 1.06%, quenched and tempered at various temperatures, experimental equations representing the relation between diffraction line width and hardness were obtained as a function of carbon content. The halfwidth and the Gaussian curve parameter (GCP), that is a constant of a Gaussian curve fitted to a diffraction line peak, were used to evaluate the diffraction line width.
The curve representing the relation between the line width and hardness had a bend at the tempering temperature of about 400°C. At this temperature the martensitic structure of tempered steels changed into troostite or sorbite, which has a ferritic matrix. The relation between the half-width and the GCP was also given.
