Sliding tests of mechanical seals were performed by lubrication with water and using a dense test specimen, test specimens with dispersed pores, and machined porous test specimens. In the tests, the influence of the presence of pores on sliding surfaces and of the diameter of pores was determined. Machined porous test specimens were prepared by machining dense test specimens so that pores would be imparted to their sliding surface. The surface roughness and the pore surface ratio of the porous region were similar to those of test specimens with dispersed pores. Results obtained by sliding tests indicated that in cases where the pore surface ratio was 8%, test specimens with pores of less than 40μm on their sliding surfaces showed a reduction of the coefficient of friction, a reduction of temperature in the region adjacent to the sliding surface, and better stability than those of dense test specimens, which completely excluded the development of leakage. It was found that there exist two regions, a region in which the coefficient of friction and temperature adjacent to the sliding surface depended on the pore diameter and a region in which such dependence was absent. The presence of pores on the sliding surface reduced the dimensionless characteristic value G (G{sub}(min)) at which the coefficient of friction would be minimal by about 1×10{sup}(-8) as compared to that of a dense test specimen.
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