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The structure and properties of electroless Ni–Mo–Cr–P coatings on copper alloy



In the present study, the quaternary Ni–Mo–Cr–P alloy coatings were deposited on copper alloy by an electroless deposition process. Crystallization behavior and the effect of heat-treatment on hardness and corrosion resistance of Ni–Mo–Cr–P deposits were detailedly investigated. X-ray diffraction (XRD) analysis shows that as-deposited Ni–Mo–Cr–P coatings are Ni–Mo–Cr–P solid solution and mixed crystal structure; the trend of microcrystallinity increases with the introduction of additional types of metal element; Ni–Mo–Cr–P alloy coatings start to occur in the crystallization with the heat-treatment temperature increasing. With an increase in the annealing temperature, the hardness improves and reaches the maximum value at 500 °C. Further, it is found that Ni–Mo–Cr–P coatings have superior corrosion resistance than Ni–P and Ni–Mo–P deposits after the analysis of electrochemical measurements. Moreover, corrosion resistance increases before annealed at 400 °C, but heat-treatment at higher temperatures has a negative effect on the corrosion resistance of Ni–Mo–Cr–P alloy coatings.