Abstract
Electroplated hard chrome coating is widely used as a wear resistant coating to prolong the life of mechanical components. However, the electroplating process generates hexavalent chromium ion which is known carcinogen. Hence, there is a major effort throughout the electroplating industry to replace hard chrome coating. Composite coating has been identified as suitable materials for replacement of hard chrome coating, while deposition coating prepared using traditional co-deposition techniques have relatively low particles content, but the content of particles incorporated into a coating may fundamentally affect its properties. In the present work, Ni-W/diamond composite coatings were prepared by sediment co-electrodeposition from Ni-W plating bath, containing suspended diamond particles. This study indicates that higher diamond contents could be successfully co-deposited and uniformly distributed in the Ni-W alloy matrix. The maximum hardness of Ni-W/diamond composite coatings is found to be 2249 ± 23 Hv due to the highest diamond content of 64 wt.%. The hardness could be further enhanced up to 2647 ± 25 Hv with heat treatment at 873 K for 1 h in Ar gas, which is comparable to hard chrome coatings. Moreover, the addition of diamond particles could significantly enhance the wear resistance of the coatings.
Highlights
Composite plating is a technique involving co-electrodeposition of inert particles with metal/alloy in order to promote the hardness, wear and corrosion properties of the coatings, which has a great application in the industries
We have previously demonstrated the preparation of composite coatings using sediment co-electrodeposition (SCD) method[15]
The co-electrodeposition of Ni-W and diamond was conducted in a 200 mL plating bath with aqueous bath chemistry
Summary
These SEM micrographs indicate that the uniform distribution of diamond particles throughout the deposits, and the diamond content in deposits increased with the diamond concentration in bath from 1 to 5 g L−1, while above 5 g L−1 the diamond content in deposits kept almost constant.
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