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

Abstract

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 × 10−16 m3 m−1 N−1.