Using thermal spray coating method to produce system composites (Ni-Al2O3-B4C)

Abstract

Thermal plasma spraying method was used for coating the pre-prepared surfaces of turbine blades. Nickel (Ni) was used as a base material with a fixed percentage of alumina (5%Al₂O₃), and (5,10,15,20,25%) of Boron carbide (B₄C) as reinforcement material. Cermet powders were mixed for one hour, then the coating bases of steel type (316L) were prepared and roughened using sandblasting to increase the adhesion strength between the coated materials and the base. The bonding material represented by (Ni-22% Cr-10%Al-1%Y) was sprayed with a thickness of (150µm), and then the base and reinforcement material were sprayed with a thickness of (350-400 µm). Thus, the final thickness of the prepared samples was (550-500 µm). After that, the samples were sintered at 900°C for two hours. The hardness test was applied to the samples, indicating the best hardness after sintering at (25%) reinforcement ratio of 590Hv. As for porosity, its lowest value was obtained at 7%, while the best value of adhesion strength was obtained after sintering at (25%) of B₄C. However, the results of the scanning electron microscope (SEM) showed the weakness and the presence of pores in the coating layers at the low percentage of reinforcement. While the mechanical and physical properties were improved with the increase in the percentage of reinforcement to reach the best at 25% of B₄C.