The Influence of Boron Carbide Additive on the Structure and Hardness of a Nickel-Based Coating

Abstract

Laser cladding is increasingly frequently used in various branches of mechanical engineering since it has such advantages over traditional methods of depositing coatings as high heating and cooling rates and minimal mixing of base and melting materials. Laser-clad coatings are usually characterized by a fine-grained structure and a minimal heat-affected zone. Coatings formed from the Ni–Cr–B–Si powders are also very common in industrial applications, as they have good resistance to wear, corrosion, erosion, etc. Various strengthening particles can be added to this group of powders to improve the properties of the deposited coating. Boron carbides can act as such particles since they have high hardness, thermodynamic stability, and wear resistance. In this regard, the paper investigated the influence of the 7 wt. % of boron carbide B4C addition on the structure and hardness of the NiCrBSi coating formed by laser cladding of PG-SR2 powder on the surface of 30HRA steel. Using the scanning electron microscope, the authors carried out microscopic studies of the structure of NiCrBSi and NiCrBSi–B4C coatings and presented the results of X-ray spectral microanalysis. The study shows that the structures of both coatings in the deposited state are characterized by uniformity and fine-grain structure. The investigation revealed that the samples with NiCrBSi and NiCrBSi–B4C coatings have a narrow transition zone from the deposit to the base metal. The paper presents the results of measuring the microhardness of coatings indicating a decrease in the microhardness of laser-clad nickel-based coatings with the boron carbide addition.