IMPACT-WEAR CHARACTERISTICS OF ENGINE VALVE AND VALVE SEAT INSERT MATERIALS AT HIGH-TEMPERATURE (IMPACT-WEAR TESTS OF MARTENSITIC HEAT-RESISTANT STEEL SUH3 AGAINST FE-BASE SINTERED ALLOY USING PLANE SPECIMENS)

In order to simulate the wear of the valves and valve seat inserts of automotive engines, impact wear tests were conducted using rings made of a JIS SUH 3 steel valve material and disks made of a sintered alloy valve seat insert material. Test conditions were as follows: impact e nergy of 0.588 J; normal air atmosphere; ambient temperatures of room temperature, 200 degrees C and 400 degrees C; and sliding speeds of 0 tu 0.8 m/sec. Under these conditions, very low wear was observed for b oth materials subjected tu impact without sliding. For impact with sli ding speeds over 0.4 m/sec, a bright worn surface was observed and the wear rate was severe at room temperature and 200 degrees C. However, at 400 degrees C, oxidation occurred and no acceleration of the wear r ate was observed at any sliding speed. These results can be explained in terms of the occurrence of oxidation and the mechanical properties of the test materials.