DEPOSITED THIN-FILM WEAR SENSORS - MATERIALS AND DESIGN

Vacuum deposited thin-film sensors have been developed for monitoring wear and temperature in a variety of bearing applications. The sensor typically consists of one or more metallic or insulator films. This la mination of sputtered thin-film resistance elements and thermoelectric elements with appropriate insulators is deposited directly on the bea ring surface. The thin-film package can be designed to have wear behav ior similar to that of the bearing materials, and to have a small surf ace area that conforms to the bearing contour. The wear sensor monitor s the regression of the surface, i.e. the loss of material due to wear , in the range 0.1-10 mu m (or more) over the small area that the sens or occupies. The thermoelectric sensor monitors local temperature. The effect of the materials and fabrication on the properties of the sens ors are described as they affect the electrical response and the wear characteristics. Desired properties needed by the conducting film comp onent include adequate electrical conductivity, adhesion to the insula ting layers, low ductility, adequate toughness, and hardness. The crit ical properties of the insulating film component were found to be adhe sion, low conductivity, strength, and hardness. Test results were obta ined for sliding ring and block tests in both air and oil-lubricated e nvironments. For conducting films, aluminum, platinum, tantalum, and t ype K+ and K- thermoelectric alloys were studied and are reported here . Copper and two metal silicides were also evaluated. For insulating f ilms, results on aluminum oxide, tantalum oxide, and borosilicate glas s are reported. The substrate block material was 304 stainless steel. It was found that the electrical performance of the conducting films i n the sensor package can be described using a simple electrical resist ance model. (C) 1997 Elsevier Science S.A.