A New Method for Evaluating the Bond Strength of Plasma-Sprayed NiCrBSi Coatings

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.

Different Primary Gas Flow Rates in Determining the Flattening Behavior of In-Flight Particles in Plasma-Sprayed NiCrBSi Coatings and the Resultant Microstructure and Hardness

“…These structures contain substantial amounts of B and Cr, signifying their compositions as borides and chromites with some Ni-based compounds (Table 2). Our previous works indicate that these compounds comprise CrB, Cr3B4, and Ni3B [11,21,26]. Subsequently, Figure 5e-h illustrates the distinctive morphologies observed at the P50, P60, P80, and P100 interfaces.…”

“…Figure 8 displays the optical images of etched coatings subjected to various passes, wherein each coating exhibits the presence of lamellar structures, pores, and unmelted particles. In our previous works [11,21,23], the lamellar structures found in the coating could be eliminated with effective remelting. Notably, the lamellar structures in Figure 8c,d appear slenderer compared with those presented in Figure 8a,b, which can be accredited to the tamping effect of subsequently deposited particles, whereby the pre-deposited coating is pressed and spreads more effectively.…”

“…It is widely recognized that eutectic systems exhibit a higher propensity for forming the amorphous phase than other alloy systems. NiCrBSi possesses the eutectic systems of Ni-Ni 3 B and will result in the amorphous phase within the coating after plasma spraying [21]. Among different techniques, the APS process reliably provides low-cost and high-efficiency coatings with high plasma arc temperature (>10,000 K) and ultra-high cooling speed (10 5 -10 7 K/s) [22].…”

“…Among different techniques, the APS process reliably provides low-cost and high-efficiency coatings with high plasma arc temperature (>10,000 K) and ultra-high cooling speed (10 5 -10 7 K/s) [22]. During the rapid melting and solidification process, the APS process readily forms the amorphous phase in the as-sprayed NiCrBSi coatings [11,21,23]. A comprehensive understanding of the underlying mechanism governing their formation becomes imperative to regulate the quantities of amorphous phases within the coatings, which directly influences their properties.…”

Considerations on the Wear Behavior of Vacuum-Remelted ZrO2-Reinforced Self-Fluxing Ni-Based Thermally Sprayed Alloys

“…Modifications of coating density, improvement of the inter-splat bonding, and adhesion strength to the substrate are aspects also reported in the literature [ 12 ]. Various remelting technologies have been recently investigated, such as flame [ 13 , 14 ], laser [ 15 , 16 , 17 ], plasma [ 18 , 19 ], or furnace treatment [ 6 , 15 , 20 ].…”