Microstructures of Metallic NiCrBSi Coatings Manufactured via Hybrid Plasma Spray and In Situ Laser Remelting Process

Abstract

This paper deals with coating alternatives to hard chromium plating. Thermal spraying is already used in industry, but results are not always satisfactory for reasons of porosity and microstructures. In this study, atmospheric plasma spraying (APS) and in situ laser irradiation by diode laser processes were combined to modify the structural characteristics of thick NiCrBSi alloy layers. The microstructure evolution was studied, and results show that in situ laser remelting induced the growth of a dendritic structure, which strongly decreased the porosity of as-sprayed coatings and increased the adhesion on the substrate. Moreover, no phase transition after laser treatment was observed. Lastly, a mechanical investigation demonstrated that the combination between plasma spray and in situ melting with a diode laser could result in very good mechanical properties. The increase of the laser incident power involved an increase of the mean contact pressure, along with coating hardness. The hybrid process appears to be a possible alternative to hard chromium plating, in order to protect mechanical parts, because of the improved mechanical properties of the NiCrBSi layer.

Microstructure and Wear Resistance of TIG Remelted NiCrBSi Thick Coatings

“…Some studies have proved that the thin coating can be surface modified and strengthened by remelting to eliminate the layer structure of coating, reduce the porosity, and improve the interface bonding with the substrate [8], which are beneficial for improving the coating's performance [9] and prolonging the service life of the parts [10][11][12]. Unfortunately, little attention has been paid to the remelted of thick coatings.…”

Structural features of Ni-Cr-Si-B materials obtained by different technologies

“…The self-fluxing alloys of Ni-Cr-Si-B system possess high wear resistance [1][2][3][4][5][6][7] and corrosion resistance [2][3][4][5][8][9][10] at room and higher temperatures and also high heat resistance [1,3]. Due to these properties, machine details made of these materials are widely used in aerospace industry and aircraft construction [11], atomic [3,12,13], oil and chemical industry, and metallurgy [14].…”

“…It allows to form coatings of any materials including composite coatings on surface of any complexity as well as restore the worn out machine parts surfaces. Unfortunately the disadvantages of plasma coatings are high porosity (up to 20 %) [7] and low adhesion [4,5,7,18]. It may limit their use in corrosive mediums [4,5,8] and decrease their wear-resistance.…”

“…Unfortunately the disadvantages of plasma coatings are high porosity (up to 20 %) [7] and low adhesion [4,5,7,18]. It may limit their use in corrosive mediums [4,5,8] and decrease their wear-resistance. The solution to of this problem is subsequent melting of self-fluxing coatings [2,5,7,18].…”

“…It may limit their use in corrosive mediums [4,5,8] and decrease their wear-resistance. The solution to of this problem is subsequent melting of self-fluxing coatings [2,5,7,18]. SPS is perspective technique of high-pressure sintering.…”