Abstract
The improvement of working life is the main purpose of this paper to evaluate the mechanical properties of the electroless Ni–P coatings of radial micro journal bearings. The study was carried out using different plating parameter combinations, namely, pH values of the plating solution (6, 7, and 8), deposition time (10, 20, and 30 min), and bath temperature (60, 80, and 95 °C). The structure, surface morphology, hardness, and wear resistance of the electroless Ni–P coatings were measured and analyzed. The optimum combination of plating parameters for minimum wear is a pH value of 8, deposition time of 30 min, and bath temperature of 95 °C. When the Ni–P film is annealed at 400 °C, the hardness, wear and surface roughness can get the best values of 960 HV, 0.1 mg, and 0.177 μm, respectively, and this is because the Ni–P coating has changed from an amorphous phase to a crystalline composite phase (Ni + Ni3P) structure. However, as the annealing temperature continues to increase; the hardness, wear, and surface roughness begin to deteriorate. The coherent relationship of the crystalline composite phase is broken, the grains of the Ni–P coating will grow, and the tensile stress of the Ni–P coating will increase.
Highlights
Electroless coatings, which utilize chemical catalysis and reduction reactions to solve the problems of surface treatment, are widely used in the aerospace, semiconductor, machinery, petroleum, electronic and chemical industries [1]
Wear is considered the main criterion to evaluate the mechanical performance of electroless Ni-P coating in a radial micro journal bearing
The study was carried out using different coating parameter combinations, namely, solution pH values of (6, 7 and 8), deposition time (10, 20 and 30 min) and bath temperature (60, 80 and 95oC)
Summary
Electroless coatings, which utilize chemical catalysis and reduction reactions to solve the problems of surface treatment, are widely used in the aerospace, semiconductor, machinery, petroleum, electronic and chemical industries [1]. Thin film coatings meeting the properties required by high-tech and defense industries have been prepared to improve the wear resistance and corrosion resistance of materials [2], and new plating solution compositions, the performance and processing conditions, reduction of preparation costs and improvement of electroless coating technology are electroless coating technology research topics for the future. When Jones et al [5] studied amorphous nickel-phosphorus alloys, they found the main effect of phosphorus in nickelphosphorus alloys is the overpassive behavior shifts to low potential This phenomenon increases the current density in the passive and overpassive regions. Nickel-coated micro-bearing are annealed under various temperatures (100, 200, 300, 400, 500, 600 and 700oC) at the same time to analyze the effects of the film surface microstructure, crystal properties, microhardness, roughness and abrasion tests
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