Abstract
The presence of complexing agents in the electroplating bath and post-heat treatment are two factors which influence the structure of electroplated alloy coatings. Any change in structure is accompanied by changes in coating physical and mechanical properties such as hardness. The aim of this study was to investigate the effects of complexing agents present in the electroplating bath and post-heat treatment on the hardness of electroplated Ni–Cr coatings obtained from two different baths, one containing sodium citrate as its complexing agent and the other containing dimethyl- formamide. The hardness of coatings obtained from both types of electroplating bath increased with coating chromium content. Coatings obtained from the sodium citrate bath were generally harder than those obtained from the bath containing dimethylformamide. Alloy coatings with 18 and 35%Cr were selected for this study. The hardness did not decrease after heat treatment up to about 300°C, but further increase in annealing temperature caused a sharp decrease in the hardness of deposits. This decrease in coating hardness with increase in the annealing post-heattreatment temperature was observed for all coatings.
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