Microstructure-property relationships in high chromium white iron alloys

Abstract

High chromium white irons are ferrous based alloys containing 11–30 wt-% chromium and 1.8–3.6 wt-% carbon, with molybdenum, manganese, copper, and nickel sometimes added as additional alloying elements. The microstructure of these alloys typically consists of hard primary and/or eutectic carbides in a matrix of austenite or one of its transformation products. The presence of hard alloy carbides results in excellent abrasion resistance and, consequently, these alloys are commonly used for materials handling in the mining and minerals processing industries. Alloy content, solidification parameters, and thermal processing can dramatically alter the microstructure that is produced, and this in turn can influence the properties and hence performance of white iron alloys during service. This review outlines the development of the microstructure in high chromium white irons through solidification and thermal processing. The metallurgical effects of conventional processing techniques are discussed, and advances in aspects such as alloying and cryogenic treatments covered. The results of laboratory abrasion tests are summarised, and the effect of microstructure on the wear properties are discussed. The toughness and impact resistance of white cast irons, which are often thought to represent a limiting factor in their use, is reviewed, with particular regard given to the effects of microstructural constituents.