Abstract
For the first time, Zr702 coatings were deposited onto an Al6061 alloy using a high-pressure cold spray (HPCS) system. In this work, five different N2 process gas temperatures between 700 and 1100 °C were employed to understand the formation of cold sprayed (CS) Zr coatings and their feasibility for enhanced wear resistance. Results indicated that the N2 processing gas temperature of about 1100 °C enabled a higher degree of particle thermal softening, which created a dense, robust, oxide- and defect-free Zr coating. Across all CS Zr coatings, there was a refinement of crystallinity, which was attributed to the severe localized plastic deformation of the powder particles. The enhanced thermal boost up zone at the inter-particle boundaries and decreased recoverable elastic strain were accountable for the inter-particle bonding of the coatings at higher process gas temperatures. The flattening ratio (ε) increased as a function of temperature, implying that there was a greater degree of plastic deformation at higher N2 gas temperatures. The microhardness readings and wear volume of the coatings were also improved as a function of process gas temperature. In this work, the wear of the Al6061 alloy substrate was mainly plowing-based, whereas the Zr CS substrates demonstrated a gradual change of abrasive to adhesive wear. From our findings, the preparation of CS Zr coatings was a feasible method of enhancing the wear resistance of Al-based alloys.
Highlights
Being one of the most widely used metals globally, aluminum (Al) has tremendously impacted an extensive array of industries spanning from aerospace to the automotive and medical sectors [1,2]
This is quite evident from visually inspecting the bonding features between the coating to the Al6061 plate as well as the bonding between the deformed particles where the particles along all coatings exhibit a uniform flattened morphology
Upon closer inspection, it can be seen that extruded lips from the impacted particles are present along the Zr-Al interface. This phenomenon can be largely attributed to having an oxide-free interface, where the cold sprayed (CS) coating will have strong mechanical interlocking to the alloy substrate ensuring a high adhesion strength [33,38]
Summary
Being one of the most widely used metals globally, aluminum (Al) has tremendously impacted an extensive array of industries spanning from aerospace to the automotive and medical sectors [1,2]. The bond strength of CS coatings has been reported to be exceptionally high across a variety of material substrates compared to other thermal-spray technologies This is largely due to the compressive stresses that are generated from the mechanical interlocking and peening-like effects of the impacted particles, whereas tensile stresses occur from the particle heating of more thermal-based technologies [21,24,29]. Each material system should be thoroughly studied in order to fully understand their behaviors from the deposition process to tribological testing In this work, this was achieved with Zr where its structural quality and tribo-performance was studied as a function of propellant N2 gas temperature. This work will contribute to the field of CS research and further the scientific understanding of Zr when subjected to the CS process
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