No abstract

The development of optical mold coatings has become a key technology in precision optical components in recent years. Researchers are still seeking ideal electroforming materials capable of resisting higher temperature and improve the lifespan of optical mold. Examples of these materials include Ni-W, and Ni-Mo-P alloy plating, among others. However, the literature rarely mentions these alloys as protective coatings. This may be because coating stability, flatness, and strength cannot achieve the desired protective effects. This study develops a combination of two wet electrochemical processes to form a multi-layer coating on optical molds. This coating consists of Ni-W, and Ni-Mo-P alloys. The proposed treatment process attempts to enhance the mechanical strength of the mold and extend its lifespan. We first used electro-deposition to form a thick-film Ni-W coating, and then applied the electroless plating by nonisothermal deposition method (NITD) to create a Ni-Mo-P thin-film and form a multi-layer coating. We also measured the composition, hardness, and elastic modulus of the protective coating as a reference basis for the development of optical molds. The results of this study reveal the appropriate process parameters to provide the multilayer films with a high strength and flat surface. This article can serve as a reference for the development of optical mold coatings.

In this study, the SiC particles with a mean diameter of 300nm were used to be codeposited with Ni-P base to produce Ni-P-SiC composite coatings by means of the pulse current electroforming technology. The relationship between the SiC particles and phosphorous contents in the composite coatings has been constructed. The wear behavior of the Ni-P-SiC composite coatings was examined by that measurements data including the wear weight loss, the coefficient of friction, and the temperature increments under the wear tests, in which were correlated to the observation and analysis of the worn surface of the composite coatings. Experimental results show that the wear resistance of Ni-P-SiC composite coatings is superior to Ni-P composite coatings, if they are under the same level of hardness. In addition, the wear weight loss of Ni-P-SiC composite coatings is even about 62% less than that of Ni-P composite coatings, if they are based on the same production conditions. Further more, both the hardness and wear resistance of Ni-P-SiC composite coatings are superior to pure Ni coating, wherein its wear resistance is even up to 10 times better than that of pure Ni coating.

This study prepared samples with femtosecond(fs)-laser-induced periodic surface structures (LIPSSs) controlled by laser power (or peak fluence, F0) and overlap ratio (OR) to improve the friction and wear behavior of the SKD 61 tool steel sliding against a hard Si3N4 ceramic counterface in oil lubrications. Pin-on-plate (pin: Si3N4; plate: SKD 61 steel) tribological tests were conducted with the reciprocating motion perpendicular to the laser scanning direction and having an incline angle (40°∼50°) with respect to the LIPSSs. The contact angles (θ) formed on the textured surfaces were measured for an oil lubricant. The (θ)oil results were found to have their correlation with the areal surface roughness (Sa), skewness (Sk), and kurtosis (Ku) of the textured surfaces produced at various F0 and OR values. The mean friction coefficient (μ) and wear loss (W) of the steel specimens in oil lubrications are reduced by decreasing contact angle, (θ)oil. The combined effect of F0 and OR on the (θ)oil and the (θ)oil effect on μ and W are thus linked together, and the correlation provides an efficient and convenient way in the choices of laser operating conditions with the minimum μ and W. The minimum values of μ (=0.0089) and W (=2.124 × 104 μm3) were obtained with OR = 50% and a laser power of 17 mW.

Nickel-tungsten (Ni-W) plating process exhibited fewer environmental hazards and lower health hazards than conventional chromium bath processes did, because they had the potential to be substituted for certain future applications. This study attempted to develop Ni-W alloy coatings with different weight percentages of tungsten to produce by using nickel-tungsten citrate electrolyte baths that are deposited by pulse current power source techniques. The composition of the ratio of tungsten/nickel was controlled by the change from ion mass transfer rates for the interface between cathodes and electrolytes that were caused by adjustment by charging the over potential or rest that was regulated by the on-off time during pulse and reverse-pulse current. In this study, the corrosion resistance and the composition of the coatings related to the operating parameters were also discussed through the analyses of the experimental design method. Results were found that Ni-W alloy compositions governed through regulation of pulse and pulse-reverse parameters. The frequencies of electric current, Ton and Toff with pulse duty cycles had great impact on chemical composition and surface morphology for the deposits. Results of the electrochemical tests indicated the pulse plated Ni-W metal alloy coatings in which the corrosion resistance was superior to that of the alloy deposited by the direct current technique.