The influence of Re content on microstructure, grain size, microhardness and abrasion resistance of electrodeposited Ni-Re alloy coatings

Ni-Re alloy coatings with Re-content of 0-80 wt% were plated by electrodeposition from Watts's type and citrate solutions by changing deposition parameters. The microstructure, crystallographic texture, deposition rate, grain size, microhardness and abrasion resistance of the alloys were studied. The results showed that the cross-section of Ni-Re alloys with low Re-content of 5-41 wt% was dense and homogeneous. However, the cross-section of the alloys with high Re-content of 55-80 wt% showed the microcracking penetrated through the entire coating thickness. With the increase of Re-content, the coatings were composed of fine nanocrystalline structure, and the grain size decreased, even the coating with 36-80 wt% Re comprised amorphous and nanocrystalline structure. The deposition rate of the deposit from citrate solution was higher than that of the coating from Watts's solution. The coatings obtained from Watts's solution exhibited (220) preferential orientation, however, the deposits produced from citrate solution showed oriented-(111) crystal plane. The microhardness of Ni-Re alloys gradually increased with the increase of Re-content in the deposits. The wear coefficient of Ni-Re alloys gradually decreased with the increase of Re-content. Ni-Re alloy coating with 80 wt% Re exhibited the best abrasion resistance, and had the lowest wear coefficient of about 6.2 x 10(-16) m(3) m(-1) N-1.

Automated summary

Ni-Re alloy coatings were electrodeposited from Watts's type and citrate solutions, with Re-content ranging from 0 to 80 wt%. The microstructure, crystallographic texture, deposition rate, grain size, microhardness, and abrasion resistance of the coatings were investigated. The results revealed that high Re-content led to microcracking in the coatings, while low Re-content resulted in dense and homogeneous coatings. Increasing Re-content created fine nanocrystalline structures with smaller grain sizes. The deposition rate was higher in the citrate solution than in the Watts's solution. The microhardness increased with Re-content, and the wear coefficient decreased. A Ni-Re alloy coating with 80 wt% Re exhibited the best abrasion resistance, with the lowest wear coefficient of approximately 6.2 x 10(-16) m(3) m(-1) N-1.