To clarify the dangerous surface damage in mechanical seals, both sliding wear and vibratory cavitation erosion tests were performed on sintered carbon materials. The differences in damage between cavitation erosion and sliding wear were investigated through observation of surface topographies and volume losses. Roughness, Ra, of worn surface is rather small, about 1 μm in the worst case, and is independent of the worn depth. In cavitation erosion, however, Ra of eroded surface increases rapidly and thereafter attains a large steady value (3.6 μm- 11 μm for various carbon materials) with increasing eroded depth regardless of the cavitation intensity. The sliding surfaces of actual operating mechanical seals were compared with our test results and thus it was concluded that the severe damage in the mechanical seals is caused by the concentrated repetition of cavitation erosion. Furthermore, the wear and cavitation erosion resistance were compared among the various carbon seal materials. From these results, it has become clear that the cavitation erosion test is important to find out the quality of mechanical seal materials.

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