Superhard Coatings for Bearings
Abstract
The object of the work to produce cubic boron nitride (cBN) coatings in types 17-4 and 440 stainless steel used in spherical rod end bearings. The coatings were formed on these and other substrates by ion-assisted physical vapor deposition. Infrared absorption spectra of coatings on silicon substrates showed the presence of th cubic modification of BN. Indentation measurements, by a special technique that separates the contribution of the film from that of the substrate, demonstrated high microhardness values. Motor-driven feedthroughs were installed in the vacuum chamber in preparation for the coating of spherical bearing components. Sample coupons submitted to the sponsor were found by a scratch test technique to show poor adhesion to the stainless steel. The remainder of the program was therefore devoted to improvement of the coating- substrate bond. Tensile bond strength values as high as 6,700 lb/ sq in were attained. Some time after completion of the experimental work, however, it was found that the coatings were cracking into minute fragment and spalling off the substrates. The failure mechanism remains to be determined.
Document Details
- Document Type
- Technical Report
- Publication Date
- Nov 05, 1990
- Accession Number
- ADA242476
Entities
People
- Charles Feldman
- Fred Ordway