ZIRCONIUM AND NIOBIUM CARBIDE COATINGS ON NIOBIUM, TANTALUM, MOLYBDENUM, AND TUNGSTEN,
Abstract
Several methods of obtaining ZrC and NbC coatings on refractory metals were investigated. The method of obtaining ZrC and NbC coatings, involving deposition of a Zr or Nb layer on a Mo, Nb, or W sutstrate with diffusion impregnation from a solid phase using NH(subscript 4)Cl activation agent and subsequent carburizing at 1300-1700 degrees C for 0.5-5 hr., was found to be unsatisfactory because the diffusion impregnation of Nb, Mo, and W substrates proceeded very slowly, and led to the formation of solid solutions of the metals on the substrate surfaces. This made it almost impossible to obtain sufficiently thick layers of pure Nb or Zr on the surface of Mo, Nb and W substrates. Satisfactory Nb coating on Mo and W substrates were obtained by vapor deposition with an electron beam unit. Dense, strongly adhering niobium coatings with a porosity of less than 5 percent and a microhardness almost equal to that of pure Nb, were obtained in 2 hr on substrates at 500-600 degrees C. Attempts to obtain Zr coatings by the same method were unsuccessful. In obtaining ZrC and NbC coatings by vacuum sintering of degassed Nb, Ta, Mo and W specimens coated with a mixture of bentonite with carbide powder, satisfactory NbC coatings were obtained on Ta; in all other cases the reaction between the carbide powder and substrate resulted in the formation of intermediate phases.
Document Details
- Document Type
- Technical Report
- Publication Date
- May 05, 1969
- Accession Number
- AD0694180
Entities
People
- A. L. Burykina
Organizations
- National Air and Space Intelligence Center