How the micro-mechanical stability of carbides in chromium-rich hardfacings influences the impact-abrasion resistance at elevated temperatures

Abstract

Highly loaded wear components in applications such as crushers or sieves suffer from combined impact and abrasive wear, in the worst case exaggerated by high operation temperatures. Hardfacings based on the system FeCrC with high hardphase content are promising candidates for such applications. Understanding of the influence of precipitated carbides or carbo-borides on the impact-abrasive wear resistance is therefore of high importance to increase the lifetime, decrease downtime as well as maintenance costs. In this study, two different FeCrC-based hardfacings were chosen for investigation, an FeCrC-alloy and a complex alloyed FeCrNbMoBC type. A thorough microstructural analysis was performed via scanning electron microscopy. Here, present hardphases, namely chromium carbides, chromium carbo-borides as well as niobium carbides were found. To evaluate the hardness H and Young’s modulus E nanoindentation measurements were performed and the plasticity indicating ratios H/E and H³/E² were derived. Scratch tests at elevated temperatures were performed identifying critical loads for carbide displacement and fracture. Those critical loads as well as the plasticity indexing parameters were correlated with the impact-abrasion behaviour of the two hardfacings via high-temperature cyclic impact abrasion tests up to 500°C. Results showed higher impact-abrasion resistance of the complex-alloyed FeCrC-based hardfacing due to better stability of the carbides as well as optimal ratios H/E and H³/E² indicating increased plasticity and thereby better impact resistance.