The Study Of Wear Resistance Of Tungsten/Nickel-Base Alloy Composite Coatings

This thesis studied microstructure and wear property of coatings, which were Ni60,35 % WC+Ni60,35 % Cr-WC+Ni60, by the X-ray diffraction (XRD),scanning electron microscope (SEM), microhardness, wear test and so on through the different technologies of thermal sprayed welding, thermal spraying, vacuum sintering, laser cladding. Tungsten (WC) particles were wrapped Chromium (Cr) films by D.C magnetron sputtering ,with thickness of films 3-5μm.Cr-WC-Ni60 coatings by thermal sprayed welding were better than any others, but surface smoothness was worse. Resistance to wear of Cr-WC-Ni60 coating is as much 2.26 times as WC-Ni60 coating's, which showed that Cr wrapped WC prevented WC from decomposing and increasing abradability of coating. Most of wearing mechanics were sticking and abrasive particle frictions.Coatings of thermal sprayed welding, WC and Cr-WC particles distributed in the Ni-based alloy by the embedded ways. Binding state of Coating and matrix was metallurgy. Pattern of surface was crude and big WC particles were clear after laser cladding, defects of surface were deduced and compactability was increasing. Cr around WC extended like branches .In the same technology, variation of abradability was Cr-WC-Ni60 > WC-Ni60 > Ni60, hardness manifested staircases under the protection of Cr-WC to increase of hard phase.Structure feature of Thermal spraying coatings were flake layer, among of which were oxide films in evidence. Coatings being associated with matrix were mechanical bond, which had a lot of flaws such as holes and cracks and bad quality. After laser cladding, microstructures manifested that all kinds of flaws decreased and compactability and smoothness improved, structures were both thin and even. Cladding coatings and matrix became a perfect metallurgical bonding, but the hardness of it obviously reduced because that high temperature made the coating surface structure burned loss after laser cladding in the second coating of surface. Energy spectrum analysis showed that hard phases of Cr-WC-Ni60 coating were more than WC-Ni60's because of much density of WC. When coatings were remelted, WC particles sank to par-gathered in the result of hardness deduced and abradability improved, abrasion machine occurred to evidence transition.Coatings of Vacuum sintering gained good fused. Structure turned into thinner and the quantity of eutectic compound increased, which made the solid solubility of alloying agent increased. Abradability of Cr-WC coating was increased as much 2.26 times as WC coating 's, flaws of surface were a few. three groups of tests results showed that Cr packed WC prevented WC from cracking ,improved abradability of coatings ,in these technologies, the best was Vacuum sintering...