Load Carrying Capacities of the Stainless Steel Gears with Multiple Coating Layr in Ultra-high Vacuum

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The frictional and wear characteristics of the balls, the rollers and the gears of stainless steeel (SUS440C) of which the surface layr was thermally diffused after being Sn-plated were investigated by a four-ball machine, a two-roller machine and a power-circulating gear machine under grease lubrication.Further, the gear tests were carried out in the degree of about 10^<-4>Pa. From the tests, the following results were obtained :In the four-ball tests, the seizure resistance of the ball of which the diffused layr was approximately 6mum thick was 2-4 times larger than that of the untreated ball. With respect to the mean value of the critical surface temperature at seizure on both treated and untreated balls, it was 176C for the case of grease without MoS_2 additive, 176ﾟC with 3% additive, 191ﾟC with 10% additive, and 263ﾟC with 30% additive. The critical temperature at seizure was increasintg with increasing concentration of MoS_2 additive on grease.In the two-roller tests, the seizure resistance of the roller with the diffused layr was significantly larger than that without diffused layr. The seizure resistance was decreased with increasing concentration of MoS_2 additive on grease. Further, the critical surface temperature at seizure for the case of the treated roller was higher than 400ﾟC.The variation in the critical surface temperature was comparatively smaller than that in the pV value against the conformity of contacting condition on the rollers.In the gear tests under dry friction, the running time of the treated gears at the incipient stage of destructive surface failure by wear were significantly longer than that of the untreared gear.