Study On Preparation And Properties Of Multi-Composite Coatings By Electrodeposition

Ni-W-P-SiC composite coatings were prepared by electrodeposition. The influence parameters on the composite coatings were researched by orthogonal test method and single factor analysis method. The faults such as bath composition and operating condition on the composition, microstructure, morphology, wear & friction and corrosion resistance of Ni-W-P-SiC coatings were investigated. The metallurgical microscope,scanning electron microscope(SEM),transmission electron microscope(TEM) and X-ray diffraction(XRD) were used to analysed the morphology, microstructure and composition of Ni-W-P-SiC composite coatings. The microhardness, friction wear and electrochemistry experiment were performed to analyse the mechanical, friction,wear behavior and corrosion resistance properties.The optimal electrodeposition conditions were:Na2WO4·2H2O:50g/l, NiSO4·6H2O:50g/l, C6H8O7·H2O:50g/l, NaH2PO2·H2O:10g/l, SiC:40g/l, OP-10:0.6g/l, pH:7,T:50℃,Dk:4A/d m2,stirring speed:200 r/min.The XRD show that the as-deposited composite coating has an amorphous form and transforms to crystalline after heat treatment at 400℃with the phases of Ni,SiC,Ni3P and Ni5P2.The content of the component analyzed by EDS was:Ni:78.44wt%, W:7.11wt%,P:11.45wt%,C:1.31wt%,Si:1.69wt%.The hardness and wear resistance of the Ni-W-P-SiC composite coating depends on the SiC content,and reach the best status at the content of 60g/l.(?) The coating has the highest hardness of about 1054HV when heat treated at 400℃for 3 hours.The corrosion resistance of Ni-W-P-SiC composite coatings is better than Ni-W-P coatings and steel substrate, and reachs the best corrosion resistance when the SiC addition is 60g/l. The corrosion resistance increases after heat treatment and has optimal performance when heat treated at 400℃.Ni-SiC,Ni-W-P,Ni-W-P-SiC coatings have little difference surface in morphology, and all have a typical cellular'structure; In Ni-SiC and Ni-W-P-SiC composite coating, SiC particle dispersion embedded in matrix. Ni-SiC coating exists only Ni and SiC two substances without crystalline changes. While in Ni-W-P and Ni-W-P-SiC coatings,crystalline changes with temperature changes and has new precipitation which can obviously enhance hardness of Ni-W-P-SiC composite coating.The wear resistance and corrosion resistance of Ni-W-P-SiC composite coating is better than Ni-W-P and Ni-SiC coating.