Effect of Powder Feed Rate on Mechanical Properties of Boron Carbide Coatings by Atmospheric Plasma Spraying (APS)

Boron carbide (B4C) is considered an ideal material for plasma-facing materials (PFMs) in nuclear fusion, due to a combination of excellent properties: high elastic modulus, high chemical stability, low Z and high melting point. In this paper, B4C coatings were fabricated onto tungsten (W) substrates using atmospheric plasma spraying (APS). The powder feed rate significantly affects the coating quality. The effects of different powder feed rates on the properties of sprayed coatings including thickness, porosity, and adhesion strength were investigated. The particle temperature and the particle velocity were measured by the diagnostic system DPV evolution. Phase evolution and microstructure were characterized by x-ray diffraction (XRD) and scanning electron microscopy (SEM). XRD analysis showed that the main phase composition of the coating did not change compared with the initial B4C powder, the surface of the B4C coating was oxidized and formed B2O3. It has been demonstrated that the adhesion strength of the coating increases and then decreases with the increase of powder feed rate. Under the optimal powder feed rate of 1 g/min, the optimal adhesion strength of the coating is 11.38 MPa.