ADEQUAÇÃO DA COMPOSIÇÃO QUÍMICA E DO TRATAMENTO TÉRMICO DE FERROS FUNDIDOS DE ALTO CROMO UTILIZANDO TERMODINÂMICA COMPUTACIONAL

Abstract

A methodology for using computational thermodynamics to optimize heat treatments of high chromium cast irons is presented. The main characteristics of the commercial alloys based on the Fe-Cr-C system are discussed, together with the steps to be applied using computational thermodynamics to preview microstructures and properties that can be achieved, resulting from different alloy compositions and heat treatments. The results of application of the method for two practical cases are presented. A 31%Cr alloy (all percentages are by mass, unless otherwise stated), with nitrogen addition, was developed to resist to abrasion and corrosion, a result obtained thanks to a martensitic matrix with hardness over 700 HV, containing over 14% dissolved chromium. An abrasion and impact resistant alloy was developed using computational thermodynamics to establish the chemical composition and heat treatment to obtain 0.8%Mo dissolved in the austenite previously to the quenching treatment, leading to secondary hardening during tempering.