Microstructure of Vacuum Plasma-Sprayed Boron Carbide

摘要

In the present study, boron carbide was deposited on Ti-6%Al-4%V alloy by vacuum plasma spraying. Chemical and phase compositions of the initial starting powder and the as-sprayed deposit were characterized using hot gas extraction, x-ray photoelectron spectroscopy, Raman spectroscopy, x-ray diffraction, and transmission electron microscopy. Mechanical properties of the deposition were assessed by microhardness and nanohardness indentation. The microstructure consisted of equiaxed boron carbide grains, microcrys-talline particles, and amorphous carbon regions. The amount of boron oxide and amorphous carbon in the coating was increased compared with the initial powder. The measured microhardness was slightly higher than values reported previously (1033 ± 200 HV). There was significant variation in measured nanohardness (-100 + 39 GPa) from point to point caused by multiple phases, splat boundaries, and porosity in the deposited structure. Carbon segregation to grain boundaries and/or splat boundaries in boron carbide was observed directly using spatially resolved electron energy loss spectroscopy method.