Wear and corrosion characteristics of electroless Ni–W–P–B₄C and Ni–P–B₄C coatings

Abstract

In this study, the microhardness, wear and corrosion resistance of electroless deposited Ni–W–P–B₄C, Ni–P–B₄C, Ni–W–P and Ni–P coatings on AZ91D magnesium alloy were investigated. The hardness of the Ni–W–P–B₄C and Ni–P–B₄C composite coatings was more than that of the Ni–P and Ni–W–P coatings. The Pin on disk wear test results showed that the Ni–W–P–B₄C and Ni–P–B₄C composite coatings have a better wear resistance in comparison to the Ni–W–P and Ni–P coatings. The worn surfaces exhibited a change in the wear mechanism from adhesive for the Ni–P coating to abrasive for the Ni–W–P and Ni–W–P–B₄C coatings and combination of adhesive and abrasive for the Ni–P–B₄C composite coating. Tafel test has been used to assess corrosion performance of the specimens; the Ni–W–P coatings exhibited the best corrosion resistance while the Ni–W–P–B₄C and Ni–P–B⁴C composite coatings showed less corrosion performance than the Ni–W–P and Ni–P coatings respectively.

Keywords:

• Wear
• Corrosion
• Hardness
• Friction
• Composite

Acknowledgement

The authors would like to acknowledge the financial support of Shiraz University through the grant no. 87-GR-ENG-16. We also gratefully acknowledge Dr. P. Najafisayar for his constructive remarks on this paper.