Behaviour of iron-based hardfacing alloys under abrasion and impact

Abstract

Iron-based hardfacing alloys are widely used to protect machinery equipment exposed either to pure abrasion or to a combination of abrasion and impact. The specific wear behaviour of a welding alloy under these conditions depends on its chemical composition, the microstructure obtained after welding and finally the welding technology used to apply them respectively the parameter settings which strongly influence, for example, dilution with the base material or formation of metallurgically precipitated hard phases. The main objective of this study was to evaluate the wear behaviour for pure abrasion and for combined wear of iron-based alloys which are typically applied by gas metal arc welding (GMAW). A new complex Fe–Cr–W–Mo–Nb alloy with high boron content was set into comparison with lower alloyed materials on basis Fe–Cr–B–C, a synthetic multiphase alloy on iron base with around 50 wt.% tungsten carbides and a crack free martensitic Fe–Cr–C alloy containing finely precipitated Niobium carbides. Besides these a conventional hypereutectic Fe–Cr–Nb–C alloy was integrated in the program serving as standard which is already well described in literature. In order to simulate real field conditions on a lab scale, tests were performed with a standard ASTM G65 dry-sand rubber-wheel tester (3-body abrasion). A specially designed impeller-tumbler apparatus enabled investigation of impact abrasion wear tests (combined impact and abrasion wear). The evaluation of wear behaviour was supported by micro- and macrostructural investigations and by hardness tests.