Richard Lloyd Mehan

Friction and wear of diamond materials and other ceramics against metal

Abstract Utilizing the Falex rotating ring and block technique, we evaluated the performance of several diamond materials and alumina, silicon carbide and a cemented tungsten carbide sliding against hardened steel 4620 and a nitrided 12% Cr steel. All tests were performed at 50 rev min −1 lubricated and unlubricated, in both continuous and 75° oscillating ring motion. The lubricating fluid was mineral oil with a kinematic viscosity of 72 cSt. It was found that ground diamond compacts, irrespective of the grain size in the compacts, resulted in the best combination of low friction and low metallic wear rates under both lubricated and unlubricated conditions. Metal wear resulting from diamond-metal sliding was found to be dependent on the compact surface roughness, and an initial roughness exceeding about 0.36 μm (14 μin) center-line average led to severe wear under some conditions. In the dry condition, all the ceramics showed high frictional forces and some degree of wear in both metal and ceramic, with the exception of alumina which did not itself develop a macroscopic wear scar.

The wear of selected materials in mineral oil containing a solid contaminant

Abstract In order to identify piston ring and cylinder liner materials with improved abrasive wear resistance in diesel engines, a number of materials and coatings were evaluated using a pin-on-disc apparatus. The lubricant used to simulate an abrasive-containing fuel was 2.0 /gmm Al 2 O 3 dispersed in white mineral oil. Of the materials examined, cemented WC cermets and coatings displayed the least wear, and estimates of the wear rates of these materials compared favorably with those obtained when chromium-plated pins were run against cast iron in an uncontaminated lubricant. It was found that surface finish had a significant effect on material wear in a contaminated lubricant and a smooth surface finish was desirable.

Dry sliding wear of diamond materials

Abstract In pin-on-disc tests, diamond composites, consisting of diamonds imbedded in a silicon matrix, were run against themselves in air at a sliding speed of 125 cm s −1 and for loads up to 3.6 kgf. In addition, a few experiments involving sintered diamond compacts rubbing against a rotating metal ring in a ring-and-block configuration were conducted. For the diamond composite wear tests, wear was found to be proportional to load and sliding distance for P ⩽ 3.0 kgf . For both the diamond composite and the diamond compact, the wear rates were very low and similar to those previously observed for single-crystal diamonds rubbed by diamond and metal.