Abstract
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.
Highlights
The surface modification provides significant convenience for enhancing the surface properties of metallic materials [1,2,3]
The as-sprayed NiCrBSi coating has the total area of interfacial pores of 904 ± μm2, the interfacial hardness of ± 30 HV and the bond strength of 14.45 ± 6.45 MPa, respectively
The remelting process inputs heat to the as-sprayed NiCrBSi coating, reducto the fitting curve, when the total area of the pores decreases to zero, the bond strength would increase to 61.6 MPa
Summary
The surface modification provides significant convenience for enhancing the surface properties of metallic materials [1,2,3]. For plasma spraying technology, the bond strength between the prepared coating and the substrate is a critical consideration for the final product. Two methods for measuring the bond strength of NiCrBSi coatings (as well as other plasma-sprayed coatings) are mainly reported. The bond strength of the as-sprayed NiCrBSi coating is in the range of 11~66 MPa [22,23,24]. The bond strength of the NiCrBSi coating can be considered from the microstructural features of the coating/substrate interface. We developed a qualitative approach to establish the relationship between the microstructural features of the coating/substrate interface and bond strength. NiCrBSi alloy coatings were prepared on the stainless-steel substrates by plasma spraying technology. Voltage (V) Current (A) Powder feed rate (g/min) Spray step (mm) Gun traverse rate (mm/s) Main gas Ar (slpm) Secondary gas N2 (slpm) Feed gas Ar (slpm) Spray distance (mm)
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