Carbonbon tribo-analysis on valve samples and thread taps

The present tribological analysis on worn samples from ball valve and diesel engine exhaust valve assemblies and on thread taps showed the following: most likely, the sliding surfaces of the ball valvels had been subjected to adhesive wear including transfer of material from the ball to the seal ring, and abrasive wear in the ball-seal interface. In diesel engine exhaust valve systems revealing lo wear, a surface layer of CaSO4, possibly assisted by graphite or soot, seems to have been effective for suppressing the wear of the sealing surfaces. In diesel engine exhaust valve systems subjected to high wear, surface layers consisting of CaSO4 were not detected. The dominating wear mechanism acing on the cutting edges of the wear taps was abrasion.