Effect of laser­textured groove wall interface on molybdenum coating diffusion and metallurgical bonding

Abstract The bonding mechanism of atmospheric plasma-sprayed Mo coatings on stainless steel laser-textured groove pattern substrates was investigated using experimental and simulation methods. The phase compositions of the interface layers were investigated using X-ray diffraction, while scanning electron microscopy and energy dispersive spectroscopy were used to analyze the bonding state and elemental distribution of the interface, respectively. PosiTest AT-A measured the bonding strength of the grit-blasted and laser-textured grooved substrate coatings. We developed a three-dimensional numerical model to describe the alteration in the wall temperature during droplet filling using a commercial simulation software. The results showed that the diffusion depths of the groove wall in the crater, middle, and bottom were 2.94, 2.7, and 1.89 μm, while those of the metallurgical layers were 1.44, 0.8, and 0.52 μm thick, respectively. Compared with the grit­blasted substrate coating, the bonding strength and minimum diffusion thickness of the textured substrate increased by 49.7 and 32.2%, respectively. Therefore, the groove wall interface formed a mixed metallurgy, diffusion, and mechanical bonding with the non-mechanical bonding decreasing from top to bottom. The thickness of the interface of the metallurgical and diffusion layer of the groove wall gradually decreased from the crater to the bottom. Nonetheless, the thickness and area of the textured substrate were higher than that of the grit-blasted substrate. A shallow groove was formed between the adjacent groove craters, which increased the bonding strength of the coating. Finally, we developed a mathematical model for predicting the bonding layer. This study contributes to the literature by providing significant findings of the Mo coating, thereby offering theoretical support for the interfacial bonding of the plasma-sprayed Mo coating by the laser surface texture substrate.