IMPACT-WEAR CHARACTERISTICS OF ENGINE VALVE AND VALVE SEAT INSERT MATERIALS AT HIGH-TEMPERATURE (IMPACT-WEAR TESTS OF AUSTENITIC HEAT-RESISTANT STEEL SUH36 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 SUH36 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, dry air of room temperature, 200 degrees C and 400 d egrees C, and sliding speeds of 0-0.8 m s(-1). Under these conditions, very low wear was observed for both materials subjected to impacts wi thout sliding. Under impacts with sliding at 0.1 m s(-1), a mildly bri ght worn surface was observed at room temperature, At this sliding spe ed, the rings also showed an accelerated wear rate. At 200 degrees C w ith sliding speeds over 0.4 m s(-1), a bright worn surface was observe d and the wear rate was severe. However, at 400 degrees C, oxidation o ccurred and no acceleration of the wear rate was observed at any slidi ng speed. These results can be explained by the occurrence of oxidatio n and the mechanical properties of the test materials.