Influence of oxidation on the composition and structure of the surface layer of hot-pressed boron carbide

Abstract

The oxidation of hot-pressed boron carbide under isothermal conditions and under conditions of programmed heating up to 1500°C was investigated. Oxidized samples were studied by secondary-ion mass spectrometry, X-ray photoelectron spectroscopy, scanning electron microscopy, energy-dispersive X-ray microanalysis, X-ray diffraction, and other methods. It has been demonstrated that oxidation starts above 600°C and results in the formation of a thin transparent B₂O₃ film that is cracked after cooling. Up to 1200°C, the oxidation process is limited by the diffusion of reagents through the oxide layer; at higher temperatures, it is determined by the rate of chemical reaction of carbide with oxygen in the air. During boron carbide oxidation the etching of grain boundaries occurs, it results in strength degradation at higher temperatures.