High performance steels for wear applications

One of the main problems across many industries is damage to, and possible failure of, components and products due to wear. The resulting financial losses even have a measurable impact on a country’s economy. Looking at the mining and related industries, wear causes expensive downtimes and production losses. To minimize the effect of wear it is vitally important to choose the correct material for component manufacture and steel, as a very versatile material, plays the most significant role. New high performance steels for wear applications have been developed and improved over the years and are available with different hardness levels. The steels generally feature high hardness combined with satisfactory toughness and show good surface quality and homogeneity.This paper presents an overview of the metallurgy behind the application of microalloying elements, especially Nb and Mo, in quenched or quenched and tempered wear resistant steels. The important role of Nb in controlling the austenite microstructure duing rolling and heat treatment is discussed. Additionally, the remarkable improvements in toughness and brittle fracture resistance, due to a very fine microstructure and finely dispersed Nb-carbonitrides in a martensitic microstructure, are highlighted. The improvement in strength and toughness properties is demonstrated by comparison of Nb microalloyed steels with Nb-free steels. The influence of Mo on the martensite start temperature and the start of transformation times, as well as the effect of forming high hardness, (Fe,Mo)3C is also discussed, in terms of both the hardness and through-hardening behaviour of the steel, as well as the wear behaviour. Results of mechanical testing and the newest developments are presented. Modelling is often used to predict all the microstructural effects of microalloying elements, but modern steel development also uses modelling tools to predict the final steel properties. Other modelling tools are also available to support steel selection and to determine a suitable steel grade as a function of the wear stress. One of these tools is presented in this paper. (AU) Copyright © 2018 Companhia Brasileira de Metalurgia e Mineração (CBMM) All rights reserved