S.X. Zhao

NONDESTRUCTIVE TESTING OF EAST W/Cu DIVERTOR COMPONENTS

Abstract Recently, the EAST W/Cu divertor components, including the ITER-like monoblock W/Cu units and flat-type W/Cu units, have been developed by Institute of Plasma Physics, Chinese Academy of Sciences (ASIPP) in collaboration with Advanced Technology and Materials Co., Ltd. (AT&M). To detect the bonding quality in these multiple layer geometry W/Cu plasma-facing components (PFCs) at each step of their manufacture, special nondestructive testing techniques have been researched and developed. For monoblock W/Cu PFCs, the bonding at both W-Cu and Cu-CuCrZr interfaces was qualified by spiral ultrasonic testing (UT) with a focus probe, which was inserted into the CuCrZr tube with a flexible driving tube. Artificial defects with defined size have been measured by UT and compared with the results of high heat flux testing (HHFT). The HHFT demonstrated that the monoblock W/Cu mock-up qualified by this UT has withstood 1000 cycles of heat load at 10 MW/m2. The bonding quality of flat-type W/Cu mock-ups has also been inspected by the usual water-gap UT. The results from HHFT at 5 MW/m2 demonstrated that the present UT was unreliable for the quality control of the flat-type W/Cu PFCs.

Preliminary Results of W Fiber Reinforced W (W f /W) Composites Fabricated with Powder Metallurgy

Abstract The first attempt at developing chopped W fiber-reinforced W (Wf/W) composites without an engineered interface or inter-phase employing hot isostatic pressing (HIP) has been made in order to study the feasibility of the powder metallurgy (PM) fabrication methodology. Micro-structures and flexural properties of sintered compacts have been examined by an optical microscope (OM), a scanning electron microscope (SEM) equipped with an electron back scattering diffraction (EBSD) instrument and three-point bending (3PB) tests. There are some chrysan-themum-like grains around each fiber in W matrices. Mechanical properties, namely strength and pseudo-plasticity, of the sintered compacts are far from satisfactory. Abnormal grain growth does not seem to have a preferential growing direction according to EBSD results. Possible causes for the abnormal grain growth and further mechanical property optimizations are hereby presented.

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

Abstract 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.