Effect of boron on the microstructural evolution and wear resistance of high-hardness Fe-based alloy coatings prepared by laser cladding

Abstract

One of the primary failure modes of 45 steel is severe surface wear, which significantly raises its application cost. In order to improve the wear resistance, high-hardness Fe-based alloy coatings with varying boron contents were prepared on 45 steel substrates by preplaced-powder laser cladding in this study. The effect of boron content on the phase composition and microstructural evolution of the coatings were systematically studied. The proportion, morphology, and distribution characteristics of boride phases in the coatings were discussed in detail. The results demonstrated that the Fe-based alloy coatings with different boron contents were composed of α-Fe, Cr7C3, and Fe2B phases. The boron content had a significant influence on the morphology and proportion of the boride phases. With the increase of boron content, the proportion of boride phases gradually increased and the morphology transition was reticular → cluster-shape → long strip-shape → plate-shape. The composition analysis revealed that the boride was Cr-rich Fe2B phase and the content of Cr in the borides increased with the boron content of the coating. The addition of boron could effectively improve the hardness and wear resistance of the Fe-based coatings, which could be attributed to the boride hard phases in the microstructures. The coating with 6.0 wt% B exhibited the highest microhardness and least amount of wear loss. The wear mechanism of the coating with different boron contents was also discussed.