Investigation On Preparation Of W-Cu Composite Coatings On Copper Substrate Surface By Mechanical Alloying

Surface mechanical attrition treatment (SMAT) as a new method for preparation of coatings hasbeen widely employed for the fabricating of coatings with metallic soluble material system. However,depositions of coatings with metallic immiscible material system by mechanical alloying method havehardly been reported at home and abroad so far. Based on these, this work carried out the study aboutpreparation of W-Cu composite coatings on copper substrate by mechanical alloying method.First of all, effects of different milling durations and rotation speeds on the preparation of W-Cucomposite coatings were studied in the experiment. And the formation process of coatings wasproperly discussed. Based on the optimized milling duration and rotation speed, effect of powder ratioof W and Cu on the microstructures and properties of coatings was investigated. The studies indicatedthat proper addition of ductile Cu powders could improve the cold welding capacity of themechanically milled powders, which could be beneficial to obtain coatings with excellent propertiesand increase the thickness of coatings to some extent.Optical microscope (OM), X-ray diffraction (XRD), scanning electron microscopy (SEM) andenergy dispersive X-ray spectroscopy (EDS) were used to investigate the microstructures, chemicalcompositions and phase structures of as-fabricated coatings. Micro-hardness test, scratch adhesion testand friction and wear experiment were carried out to evaluate the properties of coatings.In order to acquire W-Cu composite coatings with certain composition gradient and higher surfacehardness, the second and the third ball milling were conducted respectively by changing the powderratio on the basis of deposition of single layer W-30wt.%Cu coatings. The feasibility of preparation ofW-Cu composite gradient coatings via process of gradual addition of powders was discussed in theexperiment. The results show that a fully dense and uniform triple layer W-Cu composite gradientcoating with an average thickness of~92μm was closely bonded on the pure copper substrate afterthree times ball milling. The surface of the coating had the maximum microhardness value of~HV0.1212, showing a threefold improvement upon the pure copper substrate. The friction coefficient of thefabricated triple layer W-Cu composite gradient coating was0.5and the corresponding wear mass losswas only2.8mg, which is obviously lower than that of the copper substrate, indicating that theforming of coating enhanced the friction behavior of substrate to a large extent.This paper also mainly discussed the mechanisms of solid solubility extension of immisciblematerial system and preparation of coatings with metallic immiscible material system by mechanicalalloying method.