Technology Of Ni-P-Al₂O₃ Electroless Composite Plating And Research Of Laser Hardening On It

In this paper,27SiMn as matrix, were studied anionic (SDS) and nonionic (triethanolamine) surface active agents on electro less Ni-P-nano Al2O3 process studied, and the morphology of the coating, Plating rate, hardness, wear resistance and corrosion resistance such as a comparative study, find out the best technolegy.Base on this experiment above, choose better performance of the preparation method with Surfactant, the uniform Ni-P-nanoAl2O3 electrodes plating was prepared on the surface of 27SiMn steel, then treated by high power CO2 laser under the change of the output power from 200 to 800W, the scanning speed at 12mm/min and the spot diameter is 3.5 mm. Optical microscope and scanning electron microscope(SEM) were used to observe the morphologies of the coatings X-ray diffraction(XRD) was employed to analyze the phases and of the coating. The micro-hardness of the coatings under different laser power were tested respectively by Micro hardness. The abrasive wear resistance of the coatings under different laser power were tested by Abrasion machine. The Electrochemical workstation was used to tested the corrosion resistance of the coating under different laser power.The results reveal that:first, two ternary alloy formulations are successfully obtained 27SiMn plating Ni-P-nano-Al2O3 Composite Coatings, higher hardness, wear resistance; bath containing anionic compound obtained Coating in the plating rate, hardness, wear and corrosion resistance are better than non-ionic compound containing coating has better protection; second, the surface roughness of the coating with the increasing laser power first decreases and then increases. The phases in strengthened layer obviously changes from amorphous state to crystalline state and the phases were Ni,Ni3P and NixPy, When the power reaches 800W, NixPy disappearance completely. The whole coating is divided into four regions from surface to inner as follows:laser strengthen region, transition zone, heat affected zone and substrate. The micro-hardness and corrosion resistance of the coating with the increasing laser power first increases and then decreases. Corrosion resistance is inversely proportional with the laser power. When the power is 400W, the comprehensive performance of coating is the best.