Abstract
In this study, a multilayered hard coating with a tungsten matrix and a transition layer was deposited on pure copper by double glow plasma surface alloying technology, which aimed to provide the coating superior binding force and favorable matching of mechanical properties. The micro-hardness tester was adopted to measure the surface and cross-sectional hardness of the coatings. The nanoindentation test was used to measure the elasticity modulus of the coatings. Sliding wear tests under different conditions were performed on the W/Ta multilayer coating as well as the Cu substrate and W coating. The fairly low specific wear rate of the multilayer coating proved its excellent wear-resisting property, and the wear mechanism of the multilayer coating was mainly abrasive wear. In addition, a scratch test was executed to evaluate the deformation mechanism of the coating. Compared to the W coating, the persistence of the changing elastic–plastic deformation in the W/Ta multilayer coating improved the adhesion and resistance to plastic deformation. Moreover, the changing elastic–plastic deformation region is a benefit to the wear process, and the mechanical properties of the transition layer present a linear gradient descent instead of a vertical gradient, which makes a significant contribution in the wear stage. Further, the exploration of deformation mechanisms has a significant contribution to the design for multilayered hard coatings.
Highlights
In recent years, with the implementation of the International Thermonuclear Experimental Reactor plan, plasma-facing materials (PFM) have attracted considerable attention [1,2]
A double glow plasma surface alloying chamber was applied to deposit W/Ta multilayer coatings on pure Cu, which installed an anode and a source electrode
It is obvious that the W coating was more likely to peel during the wear process, and these peeling areas were easier to generate oxidative and adhesive wear, as evidenced by Figure 9c, bringing out a conspicuous increase of the wear rate
Summary
With the implementation of the International Thermonuclear Experimental Reactor plan, plasma-facing materials (PFM) have attracted considerable attention [1,2]. It was reported that the combination of hard alloy coating and the substrate of heat sink material have been used as the PFM of the divergent components in fusion reactors due to their high melting point, high sputtering and wear resistance, good thermal conductivity, and other outstanding comprehensive performances [3,4,5]. As an important research direction of PFM, W coating on copper substrate has very important research and application value, which can protect the vacuum interior wall and various internal components from high-temperature plasma-direct irradiation [6,7]. Various methods have been proposed in an attempt to fabricate a W coating on the. Cu substrate, such as mechanical alloying, the chemical vapor deposition (CVD) technique, and the physical vapor deposition (PVD) technique. Monclús et al [9] investigated the microstructure and mechanical properties of Cu/W multilayers deposited by balanced magnetron sputtering apparatus, and the results showed that the Coatings 2020, 10, 926; doi:10.3390/coatings10100926 www.mdpi.com/journal/coatings
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