The meaning of high stress abrasion and its application in white cast irons

Abstract

White cast irons perform much less favourably in industrial service environments such as ball mills than would be predicted by standard laboratory abrasion tests. Pin abrasive tests are widely thought to simulate high stress abrasion, but in reality they grossly over-estimate service lives of white iron mill liners compared to pearlitic steel liners. The ‘impact-abrasion’ hypothesis has suggested that the key difference between laboratory and service conditions is impact. However, we have found no evidence of such a phenomenon in ball mills, and instead the observed behaviour is attributed to high stress abrasion in the service environment. The defining characteristics of high stress abrasion are re-stated in a way that emphasises the load able to be transmitted to the wearing surface through the abrasive particle. Data are presented which indicate that abrasive wear mode can be identified from quantitative performance comparisons between key classes of wear-resistant alloys. Three useful diagnostics are proposed. Using these diagnostics it is shown that pin abrasive tests do not represent high stress abrasion in any industrially-relevant sense. Appropriately modest performance of white irons can be reproduced in various laboratory apparatus having zero or negligible impact energy: RWAT-analogues using solid metal wheels (xWAT), the Abex block-on-track apparatus, and a simple laboratory ball mill abrasion test (BMAT). Of these, the BMAT most closely reproduces the contact and particle mechanics of service conditions, and can give quantitative alloy performance comparisons closely matching those in service. This paper discusses some features of the BMAT and presents preliminary data for white cast irons.