High-temperature abrasion of boron and carbon alloyed iron aluminide claddings

Abstract

Adding boron and/or carbon to iron aluminides significantly enhances their hardness due to the formation of additional borides and carbides at thus the wear resistance at ambient and high temperature. Therefore, Fe₃Al-based claddings alloyed with either 10 or 20 at.% B, 10 at.% C, or a combination of 10 at.% B and 10 at.% C were developed using laser metal deposition (LMD). The microstructures and hot hardness of these claddings, tested up to 900 °C, were correlated with their scratch resistance at 20 °C, 500 °C, and 700 °C. The highest hardness levels among the claddings were achieved with Fe30Al20B (20 at.% B), featuring 813 ± 9 HV10, and Fe30Al10B10C (10 at.% B and 10 at.% C), exhibiting 530 ± 34 HV10. This can be attributed to the formation of Fe₂B in Fe30Al20B and perovskite-type Fe₃AlC₀.₆ in Fe30Al10B10C within the Fe₃Al matrix. Scratch results indicate, that claddings with 20 at.% B (Fe30Al20B) or a combination of 10 at.% B and 10 at.% C (Fe30Al10B10C) feature the highest scratch resistance and therefore were selected for high-temperature abrasion tests. Here, Fe30Al20B exhibits stable wear rates of approximately 0.05 mm³/m during modified ASTM G65 tests using a steel wheel counterbody at 20 °C, 500 °C, and 700 °C. In comparison, the wear rates of Fe30Al10B10C increased slightly, from 0.045 mm³/m at 20 °C to about 0.065 mm³/m at 700 °C. Here, larger, primary Fe₂B-type borides alongside smaller ones are more effective than combined perovskite-type Fe₃AlC₀.₆ carbides, smaller Fe₂B borides, and graphite nodules as observed in Fe30Al10B10C. Despite these differences, both claddings demonstrate comparable or lower wear rates than traditional hardfacing materials based on FeCrC or NiCrC, while also offering the advantages of lower density and a reduced environmental impact.