Wear and Failure Analysis of Semi-Autogenous Grinding Mill Liners

Abstract

The wear and failure analysis of shell liners of a grinding mill is investigated. Metallurgical and tribological studies were conducted on the worn liner of a semi-autogenous grinding mill in Chadormalu Industrial Complex. The chemical analysis, wear mechanism, microstructural variations and mechanical properties in different sections of the worn liner were evaluated using visual inspection, optical and scanning electron microscopes and hardness measurements. Chemical analyses indicated that the shell linear is hypereutectoid low-alloy chromium steel. According to visual inspection, it was observed that the maximum weight loss happened in the lifter zone where the grinding mill charge is thrown on. In addition, the microstructure and hardness of the lifter of liner from the initial surface to interior depth have meaningful differences that can intensify the wear rate. The main microstructure at the initial working surface consisted of tempered martensite with noticeable content of retained austenite with hardness more than 47 HRC. The well-worn surfaces had coarse pearlitic features with cementite networks at the prior austenite grain boundaries with 29 HRC hardness. It was concluded that both the retained austenite in martensitic matrix and cementite networks in coarse pearlite decreased wear resistance severely. For improvement of wear behavior of the casting, lowering the carbon and chromium contents and applying proper heat treatment cycle to obtain a fully pearlitic microstructure with 34–40 HRC are recommended.