An article includes a monolithic substrate and a coating on the monolithic substrate. The monolithic substrate is selected from graphite, silicon carbide, silicon carbide nitride, silicon nitride carbide, and silicon nitride. The coating has a free, exposed surface and includes a compound of aluminum (Al), boron (B) and nitrogen (N) in a continuous chemically bonded network having Al—N bonds and B—N bonds. The compound includes an atom of nitrogen covalently bonded to an atom of boron and an atom of aluminum, and the compound has a composition BxAl(1-x)N, where x is 0.001 to 0.999.