A study on the surface treatment of “Calmax” tool steel by a plasma transferred arc (PTA) process

A tool steel (Calmax of Uddeholm) was subjected to surface melting using the plasma transferred arc (PTA) process. Single and multiple run melting was used under different working conditions and the geometric characteristics of melted and heat affected zones were studied as a function of working parameters, current, travel speed and gas flow rate. The parameters were adjusted in order to obtain hard layers with sufficient thickness, presenting at the same time low roughness and crack free surfaces. The same steel was subjected to a conventional heat treatment (quenching and tempering) for comparison. The PTA surface treated specimens showed fine martensitic microstructures in depth going up to 1.5E−3 m. Their hardness was higher than the one of the conventionally heat treated steel. Pin on disk wear testing showed that PTA treated specimens have much better wear resistance, attributed mainly to the fine microstructure.