Production of article coated with pyrolytic boron nitride

Abstract

Abstract PURPOSE:To contrive prevention of a coating layer from cracking or peeling by repeated heating cooling, by specifying bulk density and surface roughness of a graphite substrate and thickness of the coating layer in producing the titled article using graphite as the substrate. CONSTITUTION:The surface of a graphite substrate is coated with boron nitride by a chemical vapor pyrolytic method using a boron halide gas and ammonia gas as raw materials. In the process, a graphite substrate having 1.70-1.95g/cm<3> bulk density and >=10mu surface roughness (Rmax) is used as the graphite substrate and the thickness of the pyrolytic boron nitride coating layer is 10-300mu. In this case, if the bulk density of the graphite substrate is beyond the afore- mentioned range, adhesive force of the above-mentioned coating layer to the graphite substrate is reduced to <2.0MPa. If the surface roughness if <10mu, the adhesive force cannot be increased to >=2.0MPa, possibly resulting in natural peeling. Furthermore, the thickness of the afore-mentioned coating layer is <10mu, the graphite readily diffuses through the coating layer to emerge into the outside and reduce resistance to heating.cooling cycle. On the other hand, if the thickness exceeds 300mu, residual stress in the coating layer is increased to readily cause natural peeling.

Inventors

• 👤 Kenji Kadota
• 👤 Yoshimitsu Kawagoe
• 👤 Hiroaki Tanji

Bibliographic Details