Characteristics of microstructure and performance of laser-treated electroless Ni-P/Ni-W-P duplex coatings
(1. Light Industry Equipment Advanced Manufacturing and Measurement & Control Technology Laboratory,
School of Mechanical and Automobile Engineering, Shandong Polytechnic University, Ji’nan 250353, China;
2. Corrosion and Protection Centre, School of Materials, The University of Manchester, Manchester, M60 1QD, UK;
3. Zibo Institute of New Materials, Zibo 255040, China)
School of Mechanical and Automobile Engineering, Shandong Polytechnic University, Ji’nan 250353, China;
2. Corrosion and Protection Centre, School of Materials, The University of Manchester, Manchester, M60 1QD, UK;
3. Zibo Institute of New Materials, Zibo 255040, China)
Abstract: Characteristics of microstructures of electroless Ni-P/Ni-W-P duplex coatings were investigated using SEM/EDX and XRD analysis techniques. Microhardness and wear behaviour of the coatings before and after laser crystallization were evaluated by measurements of hardnesses of coating surface and cross-section, and by unlubricated friction and wear experiments. The results indicate that it is possible to prepare electroless Ni-P/Ni-W-P duplex coatings by sequential immersion in two different plating baths. After laser crystallization, the microstructures of electroless Ni-P/Ni-W-P duplex coatings present the characteristics of higher degree of crystallization and larger grain size for outer layer Ni-W-P than inner Ni-P, but outer layer has a higher hardness. The wear resistance of laser-treated duplex coatings in a given process parameter conditions is superior to the as-plated ones. Laser treatment was performed directly in air without argon protection, which provides the possibility for application of industrialized production.
Key words: electroless plating; Ni-P/Ni-W-P duplex coating; laser treatment; adhesive wear; nanocrystallization