The seizure behaviors of metal and polymer were studied under oil lubricated sliding contact. The experiments were carried out with a ball on ring wear tester. High carbon chromium steel (SUJ2) and Poly-ether-ether-ketone (PEEK) were used as the ball specimen with a diameter of 3/4”. The ring was a forging steel (SF540A). The sliding velocity was varied from 2 to 15m/s. The load was increased at a rate of 1N/s up to the maximum load of 1200N. The ring temperature was measured with a thermocouple located at 1mm blow the ring surface. The following conclusions were obtained. (1) SUJ2 transited clearly to seizure at a critical load depending on the sliding velocity. The critical load for transiting to seizure decreased with the increase of the slicing velocity. (2) PEEK didn’t transit to seizure at the lower sliding velocity less than 10m/s. At the higher sliding velocity of 15m/s, although the friction coefficient fluctuated as the load became high, PEEK didn’t clearly transit to seizure. Thus it was found that PEEK had a superior seizure-resistant property and a high potential for machine elements such as bearing material operating at high sliding velocity.

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The current material design of the IFMIF back-wall in Japan consists of F82H and SUS316L. At there, the SUS316L and F82H are welded each other. And, SUS316L part of the back wall is welded with the target assembly made of SUSU316L. Since the back-wall is operating under a high temperature and strength neutron irradiation condition (50 dpa / year), it is important to perform mechanical tests for these welds in engineering design of IFMIF. This research compared test piece A (welding speed 2000 mm / min) and B (welding speed 4000 mm /min). Both A and B did not find any harmful weld defect in the weld, but porosity of B was fewer than A. In hardness test, the distribution of different hardness was shown. In fatigue test, it was forecast that fatigue limit of B improves. But it has decreased more than A because of notching effect.

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