Yang Li

Traditional C276 alloy plates exhibit relatively poor wear resistance. Consequently, in high-wear service environments, they typically require reinforcement through additional surface coatings or wear-resistant materials. To further expand the application potential of C276 alloy in marine environments, where both corrosion resistance and wear resistance are critical, this study utilized L-PBF technology to fabricate C276 alloy specimens. The specimens were subjected to microhardness, room-temperature tensile, electrochemical corrosion, and tribological wear tests under three distinct heat treatment conditions. The results indicate that the precipitation of a Mo/W-rich μ-phase, induced by heat treatment, serves as the key factor in tailoring the material’s properties. Heat treatment was found to significantly enhance both the corrosion resistance and wear resistance of the L-PBF–fabricated C276 alloy. Specifically, the heat treatment process involving holding at 870 °C for 8 h followed by furnace cooling demonstrated the most effective strengthening effect. Under these conditions, both the microhardness and tensile strength were markedly higher than those of traditional plate specimens, thereby significantly improving the material’s damage resistance. Furthermore, the primary wear mechanisms observed in the specimens were adhesive wear and abrasive wear, accompanied by minor oxidative wear. Compared to traditional plate material, the wear rate of the heat-treated L-PBF C276 alloy was significantly reduced. This study demonstrates that appropriate heat treatment processes provide an effective pathway for tailoring the properties of L-PBF–fabricated C276 alloy components, a finding of significant importance for extending their service life and expanding their engineering applications.

To improve the high-temperature ablation resistance properties of Ta(W) refractory alloys, a novel ultra-high-temperature ceramic (UHTC) composite coating was prepared by combining the technological advantages of high-speed laser cladding (HSLC) and pack cementation (PC). Firstly, the HSLC process was employed to fabricate a (Hf, Ta)C-Ta(W) UHTC-refractory metal composite coating that had a metallurgical bonding with the Ta(W) substrate. Then, the PC process was utilized to transform the refractory metal phase in the coating into the corresponding refractory silicide (RMSi₂) phase. Consequently, the (Hf, Ta)C-TaSi₂ UHTC composite coating was successfully prepared. This new coating was ablated at a heat flux density of 8.0 MW/m² for 300 s at a surface temperature of 2300 °C, and the coating retained its structural integrity. The linear ablation rate of the coating is -0.67 µm/s. The ablated coating exhibits three distinct oxide layers: a loose HfO₂ top layer, a dense HfO₂ middle layer, and a slightly oxidized (Hf, Ta)C_xO_y - Hf-Ta-O glassy layer. The synergistic effect of HfO₂ and Hf-Ta-O glassy oxide film endows the coating with excellent anti-ablation resistance. This innovative design of the UHTC-RMSi₂ composite coating provides robust protection to the Ta(W) substrate from ultra-high temperature ablation and mechanical scouring.

Improving the current-carrying friction and wear resistance of copper alloy current-carrying friction subsets effectively is a hot topic. In this paper, a method of preparing high melting point molybdenum-based coating on copper alloy surfaces by laser cladding technology is presented. A large current (106 A/m2) comparison experiment is carried out with a self-made current-carrying friction device, and the failure mechanism is analyzed. The results show that the molybdenum-based coating significantly improves the adhesion problem between the friction partner and the copper alloy substrate, while the thickness of the stress layer caused by the current-carrying friction is reduced by about 7 times. The molybdenum-based coating significantly reduces the surface arc rate and has a lower friction interface temperature, thus retaining the Al2O3 self-lubricating phase. The research in this paper is expected to provide extended research ideas for the surface protection of current-carrying friction subsets of copper alloys.

Ultra-high temperature ceramic (UHTC) coatings are used to protect the hot-end components of hypervelocity aerocrafts from thermal ablation. This study provides a new approach to fabricate UHTC coatings with high speed laser cladding (HSLC) technology, and places more emphasis on investigating the formation mechanism, phase compositions, and mechanical properties of HSLC-UHTC coatings. Results show that a well-bonded interface between the coating and the tantalum alloy substrate can be formed. The coating is mainly composed of (Zr, Ta)C ceramic solid solution phase with a content of higher than 90% by volume and Ta(W) metal solid solution phase. At a relatively high powder feeding rate, the ZrC ceramic phase appears in the coating while a dense ZrC UHTC top layer with a thickness of up to ~ 50 μm is successfully fabricated. As for the mechanical properties of the HSLC coatings, the fracture toughness of the coating decreases with the increase of powder feeding rate. The increase of carbide solid solution phase can significantly improve the high temperature microhardness (552.7 ± 1.8 HV_0.5 @ 1000℃). The innovative design of HSLC ZrC-based coatings on refractory alloys accomplishes continuous transitions on microstructure and properties from the substrate to the UHTC top layer, which is a very promising candidate scheme for thermal protection coating.