Abstract
The plasma sprayed Fe-based Ni/WC composite coating on the surface of 45 steel was post-treated by laser remelting with the addition of nano-SiC. The effect of laser power on the interface microstructure of a laser remelting nano-SiC modified Fe-based Ni/WC composite coatings were researched. The metallographic structure, microscopic morphology, phase composition, and microhardness of the remelted layer were visually analyzed by metallographic microscope, scanning electron microscope (SEM), X-ray diffractometer (XRD), and microhardness tester, respectively. The results showed that the nano-SiC modified remelted coating was smooth and compact, and with no fine cracks. The remelted layer was mainly composed of [Fe,Ni], Cr, Fe0.04Ni0.36 phase. The metal elements Fe, Ni, Cr, and Si, and non-metallic element C, appeared to diffuse, and there was metallurgical bonding between the coating and the matrix. With the increase of laser power, the smaller the average grain size, the wider the half-peak height (FWHM), and the more obvious the grain refinement. When the laser power was 500 W, the interface metallurgical showed the best effect. Furthermore, the nano-sized SiC particles served as the core of the heterogeneous nucleation to refine the grains on the one hand, and promoted the formation of a hard intermediate phase in the coating on the other hand. Therefore, the laser remelting and the addition of nano-SiC particles greatly improved the microhardness of the coating. The larger the laser power, the smaller the microstructure characteristics and the fewer the number of holes. With increasing laser power, the hardness increased in general terms and the maximum hardness increased by 51%.
Highlights
As a key surface strengthening and protection method, thermal spraying technology has been widely used to prepare wear-resistant layers, corrosion-resistant layers, various functional coatings [1,2,3], and repair or remanufacture crankshafts, plungers, boilers, tubes, aircraft, ships, etc. [4,5]
González et al [6] studied the laser remelting of the NiCrBSi alloy coating on the surface of a grey cast iron and found that the treated coating was well bonded to the substrate, with almost no pores and cracks
The microstructure, phase composition, element distribution, and micro-hardness of the interface between the coating and substrate were analyzed to provide a theoretical basis for the application and popularization of laser remelting in the field of thermal spraying
Summary
As a key surface strengthening and protection method, thermal spraying technology has been widely used to prepare wear-resistant layers, corrosion-resistant layers, various functional coatings [1,2,3], and repair or remanufacture crankshafts, plungers, boilers, tubes, aircraft, ships, etc. [4,5]. This research showed that the remaining WC particles were eliminated after remelting, cracking was reduced, the cladding surface was smooth, the micro-hardness of the remelted area is reduced by 50 HV0.1 compared to that formed by laser cladding, and the carbide is assimilated to improve the compactness of the coating. As it is well-known, the mechanical properties and the crack problems are the most uncontrollable problems for the coatings. The microstructure, phase composition, element distribution, and micro-hardness of the interface between the coating and substrate were analyzed to provide a theoretical basis for the application and popularization of laser remelting in the field of thermal spraying
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