Microstructure And Wear Behavior Of Ni-based Hardfacing Reinfored With Tungsten Carbides By PTAW

In order to improve the surface wear resistance, the abrasion-resistant alloy was deposited on the surface of material. Sometimes for special performance, such as high stress abrasion resistance, it can be adding carbide particle in it. For the Ni-based hardfacing, the carbide particle usually was tungsten carbides. There are some reasons for this. On the one hand, the tungsten carbides has high corrosion resistance, high hardness, high melting point, good weldability and plastic deformation. On the other hand, the Ni-based alloy has good wettability with tungsten carbides. It adopts plasma transferred arc welding (PTAW) in this paper, the reason is that it has lower dilution and deformation, good weld formation, process stability, easy to realize automation, excellent bonding with substrate and dense and defect-free deposits.The Ni-based hardfacings reinforeced with tungsten carbides were deposited on austenitic stainless steel substrate by plasma transferred arc welding (PTAW). The optical microscope (OM), scanning electron microscope (SEM) with Energy Disperse Spectroscopy (EDS), electron probe microanalyzer (EPMA), X-ray diffraction (XRD), X-ray fluorescence spectrum analyzer (XRF), infrared carbon sulfur analyzer, microhardness tester and sliding wear tester were employed to analysis the microstrcture and wear resistance.The influence of current on microstructure and wear resistance of Ni-based hardfacing was studied. The results indicated that dendrites constituents was becoming more and more unconspicuous, the herringbone, feathery and dot community structure were appeared in coatings and the microhardness was decreased with the increase of the current.The microstructure and wear resistance of the Ni-based alloy reinforced with different content and shape of tungsten carbide were researched. In the aspect of microstructure, with the increasing content of tungsten carbides, in the shape of acicular constituent, block tissue, long flake and skeleton structures, which including element of W, were precipitated in coatings. In terms of wear resistance, the wear resistance of coatings increased, with the increasing content of tungsten carbides. At the same time, the reinforcement effect of spherical tungsten carbide was better than the irregular tungsten carbides.The influence of current on microstructure and wear resistance of Ni-based hardfacing reinforced with tungsten carbides were researched. In different welding current, the diffusion rate of element was different during the solidification of coatings, leading to various forms of organization appeared in the coatings. In terms of wear resistance, the wear resistance of coating was not monotonic function of current, it related to the current and the size of the test load. The dissolved tungsten carbides with different degree were found in coatings. They reacted with the elements of Ni-based alloys to form low melting eutectics, which precipitated in different shapes. What is more, the dissolved phenomenon of tungsten carbides was more obviously with the increase of the current.