Influence of B4C and BN additives on the structure and wear resistance of coatings produced by short-pulse laser cladding of a Ta- and SiC-based powder mixture

The most rational approach in the production of friction units is not to manufacture the entire part from high-quality materials but to apply thin coatings (up to hundreds of micrometers) from expensive materials onto steels already widely used in industry. One such expensive material is Ta. This paper presents the results of a study on the structure of coatings formed by short-pulse laser cladding of Ta, SiC, B₄C, and BN powders onto 40Kh steel. The results demonstrate the technical feasibility of producing coatings of such composition using short-pulse laser radiation. Coatings based on the Ta and SiC powder mixture without B₄C and BN additions exhibit large pores that connect into channels after cladding, while the chemical elements are distributed uniformly over the surface. In particular, Fe atoms, which were not part of the initial powder mixture, were transferred from the steel substrate, indicating strong adhesion between the coating and the substrate. The addition of B₄C and BN powders led to the formation of separate elliptical pores within the coating. The coating with the lowest content of the Ta and SiC powder mixture demonstrated the smoothest surface. Wear resistance tests revealed a positive influence of B₄C and BN on the tribological properties of the coating based on Ta and SiC powders. The minimum mass loss values for both the “pin” and “plate” specimens were obtained after testing the coating with the maximum B₄C and BN content. Although the TaSiC coating without additives experienced significantly greater mass loss, it was still 1.8 times lower than that of the uncoated 40Kh steel.