The impact fretting wear of a nuclear reactor component

In the pressurized CO2 advanced gas-cooled reactor several components are subject to gas-flow-induced vibration and wear. The impact fretting wear behaviour of two such components, which form a Nimonic PE16-stainless steel pair, was studied in the present work. Experiments were carried out to assess the wear rate dependence on test duration, temperature and gas composition and to simulate the pitted scar morphology of the ex-reactor components. The impact wear behaviour is shown to be dependent on all these parameters and a transition from a severe to a mild form of wear is identified at a temperature in the range 250-4500C, the exact temperature depending on the impacting conditions and gas composition. Below the transition temperature the specific wear rate is approximately 20 times greater than that which occurs above it. Wear scars resembling the pitted morphology of those found on the ex-reactor Nimonic components have only been obtained in tests in which the Nimonic specimens were impacted against a pregalled stainless steel surface. (orig.)