The bond strength is a critical consideration for the plasma-sprayed NiCrBSi coatings. However, the conventional methods for testing the bond strength of NiCrBSi coatings always cost time and money. If there is a simple method that could predict the bond strength of the prepared NiCrBSi coatings without destroying the coatings, it would be significantly beneficial for industrial applications. In this work, a new method was proposed based on the total areas of the interfacial pores for the NiCrBSi coatings. The NiCrBSi coating was prepared by plasma spraying technology and the as-sprayed coating was subsequently remelted by plasma arc using the powers of 20 kW, 25 kW, and 30 kW, respectively. The interfacial microstructures, the size distributions and total areas of the interfacial pores, interfacial hardness, and bond strength of all prepared coating samples were investigated. After remelting, the number and the total area of interfacial pores decrease with increasing the remelting power. Correspondingly, the interfacial hardness and bond strength of coatings increase with increasing the remelting power The bond strength of coatings basically has a linear relationship with the total area of interfacial pores. The built relationship may be used to predict the bond strength of NiCrBSi coatings.

The flattening behavior of in-flight particles during plasma spraying is a highly intricate process affected by numerous factors. Therefore, in this work, in-flight particles (spherical NiCrBSi powder) were collected with the water quenching process, and the morphology and composition differences between the original powder particles and the melted in-flight particles were observed using scanning electron microscopy (SEM). The particle size in various states was recorded and calculated. The internal structure of the particles was analyzed to elucidate their morphology and compositions under different flow rates of primary gas (FRPG). A coating with 1.25% porosity and a hardness of 767 HV_0.5 was achieved at the FRPG of 80 L/min. X-ray diffraction (XRD) and transmission electron microscopy (TEM) were used to characterize the microstructures of the obtained coatings. It was found that the as-sprayed coating had a certain amount of the amorphous phase. A noteworthy correlation was also established, wherein a decreased distance from the substrate, augmented spraying passes, and reduced amorphous phase content were interrelated. Concurrently, a noticeable influence of the tamping effect exerted by the in-flight particles on the coating was observed.