Influence of Interfacial Oxidation on the High-Heat-Flux Performance of HIP-Manufactured Flat-Type W/Cu Plasma-Facing Components for EAST

A hot isostatic pressing (HIP) route has been developed by the Institute of Plasma Physics of the Chinese Academy of Sciences in collaboration with the Advanced Technology & Materials Co., Ltd. for bonding W/Cu tiles to Ni-electroplated CuCrZr heat sinks. During high-heat-flux testing, in the initial stage, Cu/Ni interfacial debonding was observed. Careful analyses indicated that interfacial oxidation during encapsulation for HIP processing using tungsten inert gas (TIG) welding was the main cause of the limited fatigue lifetime. Copper oxides formed during the TIG encapsulation do not decompose during HIP at 600°C. As a result, weak bonding and even some microcracks were generated, and unfortunately these microcracks could not be detected by current industrial ultrasonic probes. An oxidation-free encapsulation technique, suitable for batch processing, has been developed to achieve a thermal fatigue lifetime of more than 1000 cycles at a heat load of 5 MW/m² for the components.