Abstract
The Ni-based coatings with different content of spherical tungsten carbide were deposited by plasma transfer arc welding (PTAW) method on 304 austenitic stainless steel sheets in this study. The microstructure and wear property of spherical tungsten carbide particle reinforced composite coatings were investigated by means of optical microscope, scanning electron microscope (SEM), X-ray diffraction (XRD), electron probe microanalysis (EPMA) and sliding wear test. It is shown that the fraction of spherical tungsten carbides has an important influence on microstructure of Ni-based overlay. The Ni40 overlay consists of γ-Ni dendrites with interdendritic Ni-based eutectics, borides and carbides improving the wear resistance. In the case of composite coatings with different content of tungsten carbide, many new phases are observed, such as Ni2W4C and NiW. In addition, there are a large number of irregular structures in composite coatings, such as acicular structure and irregular stripe organization. The results of sliding wear test indicate that the mass loss of coatings is influenced by the content of tungsten carbide. The mass loss decreases with the increase of tungsten carbide fraction. At high load, the abrasive resistance of composite coating with 60 wt. % tungsten carbide is improved about 50-fold compared to that of Ni40 overlay.
Highlights
Ni-based alloy powders are widely used in industry for manufacturing wear and corrosion resistant coatings applied in aggressive service conditions such as tribological components in mineral processing, oil exploration, power industry and cement industry [1,2,3,4]
It can be seen that the coatings deposited by plasma transfer arc welding (PTAW) exhibit cohesive, metallurgical and defect-free properties, and the thickness is in the range of 3~5 mm
The micrograph of sample A without tungsten carbide reveals continuous and sound interfaces between the substrate and the infiltrated composite layer, and primary dendritic structure with interdendritic phases is observed, as shown in Figure 2a.When spherical tungsten carbide is added to the Ni40 alloy, the tungsten carbides are depleted in vicinity of surface
Summary
Ni-based alloy powders are widely used in industry for manufacturing wear and corrosion resistant coatings applied in aggressive service conditions such as tribological components in mineral processing, oil exploration, power industry and cement industry [1,2,3,4]. Many methods for the synthesis of composite coatings have been reported, such as gas tungsten arc welding (GTAW), gas metal arc welding (GMAW), shielded metal arc welding (SMAW), submerged arc welding (SAW) and plasma transfer arc welding (PTAW) Compared with those methods, PTAW is a promising approach for depositing thick, metallurgical bonded coatings on a substrate. It offers a unique heat source for surface modification technology along with enormous potentials: low cost, high heat input, high efficiency, no need for surface pretreatment, easy operation, and synchronous powder-feeding mechanism [9,10]
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