Fe-based metallic glass coatings with suppressed cracks and enhanced wear resistance prepared by extreme high-speed laser cladding

Abstract

Fe-based metallic glass (MG) coatings draw great attentions due to their excellent wear resistance. The recently developed extreme high-speed laser cladding (EHLC) provides a promising method for their fabrication but limited by the strong tendency to crack. Besides that, the deep insight into the structure evolution and the failure mechanism of the coating is still lacked. Thus, the understanding of the crack origin and the prevention of crack are of great importance. In the present work, Fe-Mo-Cr-Y-C-B MG coatings with adjustable glassy phase content were successfully fabricated by EHLC. The microstructure characterization of the coatings reveals that the cracks is main caused by the hard and brittle nanocrystalline phases precipitations of monoclinic Mo12Fe22C10 and (Fe, Cr)23C6 carbides in the heat affected zone. Therefore, the cracking of the coatings can be effectively reduced by increasing the glassy phase content. Subsequently, the hardness distribution, wear performance and wear mechanism of the coatings were investigated. The results showed that increasing the glassy phase content can effectively achieve low wear rate. The prepared Fe-Mo-Cr-Y-C-B MG coatings exhibit abrasion loss as low as 3.54·10−6 mm3 (N m)−1, which is an order of magnitude lower than that of the 45# steel substrate. The wear of the coatings is primarily attributed to the fatigue wear accompanied with slighting oxidative wear. By suppressing the brittle precipitated crystalline phases in the coating, the fatigue wear can be reduced and the wear resistance of the coatings can be improved. The present work provides insights into the crack prevention and were performance improvement of the Fe-based MG coatings prepared by EHLC.