Fretting Wear Tests of Steels in Hydrogen Gas Environment

Fretting wear tests of some steel materials under gross slip condition were conducted in hydrogen gas to obtain basic knowledge on its tribological effect. The tests were done also in nitrogen, argon, and air for comparison. The amount of wear was largest in air among these gases, and the highest insulation voltage between specimens was recorded also in air. In the gas-filled atmosphere in a hermetically-sealed vessel, where some impurities are left, wear is smaller in hydrogen than in air, but larger than in nitrogen and argon. This corresponds to the difference in insulation voltage, higher in hydrogen than in nitrogen and argon. When the gases were supplied continuously in the vicinity of the contact point at high flow rate to decrease the influence of impurities, the insulation voltage and wear decreased considerably with the supplying rate. As for a comparison on wear of the steel materials with the continuous gas supplying, the difference in wear can be attributed to specimen hardness. Furthermore, exposure of specimens to high pressure hydrogen (40 MPa, 373 K, several tens to 250 hour) prior to the fretting tests, which is a simple simulation of practical use in high pressure hydrogen, increased wear in most steels tested