Influencing Factors and Process Optimization of Al/SiC Powder-cored Wires by Plasma Transferred Wire Arc Spraying

Abstract

Wire thermal spraying, one of the significant coating preparation technologies in the field of thermal spraying, has the advantages of low cost, high material utilization rate and fast coating deposition. Powder-cored wires, with easily controllable compositions, are used as spraying materials to prepare functional coatings with special properties. Coatings prepared by traditional wire thermal spraying technologies, mainly including wire flame spraying (WFS), wire arc spraying (WAS) and plasma wire spraying, have some defects, such as weak bonding strength and high porosity. In this paper, the plasma transferred wire arc spraying (PTWAS) technology was innovatively proposed, by which Al/SiC powder-cored wires were successfully sprayed to deposit the aluminum (Al)/Nicalon (SiC) composite coating. Furthermore, the influences of spraying current (I), argon (Ar) flow rate (L_Ar), hydrogen (H₂) flow rate (L_H2) and other factors on Al/Sic powder-cored wires prepared by PTWAS and the optimization of the coating preparation process were mainly studied via the single factor method and the response surface methodology. After experimental exploration and analysis, the optimized process parameters were finally determined as follows: L_Ar was 120 L min⁻¹, I was 160 A, L_H2 was 5 L min⁻¹, the spraying distance was 100 mm, the wire feeding speed (V) was 0.18 m s⁻¹, and the distance between the wire and nozzle (d) was 10 mm. It was found in the test that the porosity of the optimized Al/SiC composite coating was only 1.6%, the average microhardness was 102 HV_0.1, and the average bonding strength was 36.5 MPa. The comprehensive properties of this coating were better than those of the Al/SiC composite coatings prepared by WFS and WAS.