The Effect of Laser Power on the Interface Microstructure of a Laser Remelting Nano-SiC Modified Fe-Based Ni/WC Composite Coating

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%.

Effect of High-Temperature-Assisted Ultrasonic Deep Rolling on Microstructure and Tribological Properties of Ni-WC Coatings

“…It can be concluded that the element diffusion phenomenon occurred at the interface between the coating and the substrate after the coupling treatment, mainly Fe and Cr diffused from the substrate to the deep rolling coating, and Ni and W diffused from the coating to the substrate. The interface between the coating and the substrate was clear and in the form of occlusion, and the main bonding mode was mechanical bonding [29,30]. After HT + UDR, the lower part of the coating was embedded with the substrate under the action of temperature field and ultrasonic extrusion pressure, which improves its bonding strength.…”

“…Coatings 2023, 13, x FOR PEER REVIEW 7 of 17 occlusion, and the main bonding mode was mechanical bonding [29,30]. After HT + UDR, the lower part of the coating was embedded with the substrate under the action of temperature field and ultrasonic extrusion pressure, which improves its bonding strength.…”

“…The gray position points 1 and 2 showed that the enrichment of Ni was the most significant, and the peak intensity of Cr and W on the surface of HT + UDR was improved. Cr and C easily formed hard phases at high temperatures, such as Cr 7 C 3 and Cr 23 C 7 compounds [30], which played an important role in improving the strength and hardness of the coatings. The W element was enriched in Point 3 and Point 4 with a silver-white color, which was composed of WC and W 2 C. WC particles were crushed under the action of the UDR surface.…”