A composite coating of high-entropy alloy composite large-grained tungsten carbide and its preparation method and application

Abstract

The invention belongs to the field of preparation of special composite coatings, and in particular relates to a composite coating of high-entropy alloy composited with large-grain tungsten carbide and its preparation method and application. The composite coating is composed of high-entropy alloy and tungsten carbide, and the tungsten carbide contains large particle tungsten carbide; the particle size of the large particle tungsten carbide is 75-150 microns. The preparation method is as follows: mixing high-entropy alloy powder and large-grain tungsten carbide according to a set ratio; preparing high-entropy alloy / large-grain tungsten carbide by laser cladding and rapid cooling. By adopting the preparation process of the present invention, the high-entropy alloy / large-grain tungsten carbide composite coating is prepared while protecting the matrix and the large-grain tungsten carbide from damage, so as to realize the uniform distribution of the large-grain tungsten carbide particles inside the composite coating, And it is suitable for large tungsten carbide particles of various qualities and various types of laser cladding equipment.

Description

technical field [0001] The invention belongs to the field of preparation of special composite coatings, and relates to a high-entropy alloy / large-particle tungsten carbide composite coating with evenly distributed large-particle WC and a preparation method and application thereof. Background technique [0002] Cast iron brake discs are the most commonly used materials in motor vehicle and rail transit braking systems. Cast iron brake discs have good friction performance, strong wear resistance and heat resistance, can resist heat cracks, resist deformation, and have good castability. However, the cast iron brake disc has low strength and generally can only withstand the braking capacity below 350 °C. And because the brake disc is exposed to the outside for a long time during use, the working environment is relatively harsh, and the temperature difference of the brake disc is relatively large. If the vehicle is parked for a long time or in a humid environment, some rust wil...

AI Technical Summary

Problems solved by technology

However, there are still many problems in the preparation of WC reinforced composite coatings: in terms of raw materials, traditional tungsten carbide-based hard facing materials mainly use iron, cobalt, nickel and their alloys as binders, but cobalt is expensive, iron, Nickel-based materials have poor stability at the bonding interface and are prone to form harmful compound inclusions. In the process of friction and wear, WC is prone to fall off; from the technical point of view, the traditional WC reinforced composite coating preparation technology is mainly spraying technology and arc welding technology. The coating prepared by spraying technology cannot produce metallurgical bonding between the composite coating and the substrate. In contrast, although arc welding technology can form a molten pool on the surface of the substrate and provide good metallurgical bonding, due to excessive energy input, The dilution of the composite coating is too high, resulting in severe deformation of the matrix, excessive dissolution of WC particles, and a reduction in the comprehensive mechanical properties; finally, because the density of WC is often higher than that of the binder, in the process of coating preparation, there is precipitation of WC particles. Bottom question

Chen Lei from Guizhou University also involved this technology in his master's thesis "The Effect of Hard Phase WC and TiC on the Microstructure and Properties of Laser Cladding High-Entropy Alloy MoFeCrTiW Coating", but his research found that when the WC content is 30% , the grains of the coating are fine and dense, the elements Mo, Ti, and W are mainly enriched in the dendrites, and the content of Fe and Cr between the dendrites is relatively high; the content of metal compounds (such as TiCr, TiCr2, etc.) in the coating is significantly reduced, and the coating A small amount of dispersed WC particles appear in the layer (the content is low, and it cannot be detected in XRD at all, and the particle size is very small); the hardness reaches the highest (about 657HV0.2), and the friction coefficient is low ( About 0.25), the amount of wear is reduced, and the wear resistance is improved; electrochemical experiments show that the self-corrosion current density of the coating becomes larger, the self-corrosion potential decreases, and the corrosion resistance decreases

[0007] So far, there has been no relevant report on the composite coating of high-entropy alloy composited with large-grained tungsten carbide

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