Solidification microstructure of plasma sprayed and remelted carbide coatings (Cr₃C₂/ni-Al, W₂C-WC/Co)

Abstract

Carbide layers applied on the steel substrate by the plasma spraying method were remelted using high-energy heat sources. A diverse methodology of coating treatment was used: ranging from a single and multiple treatment with a continuous micro-plasma arc, through the treatment by the TIG (tungsten inert gas) welding method, to CO 2 laser remelting. The quality of the remelted layers was evaluated based on macro-and microscopic structural examinations, x-ray phase analysis, tribological tests, and hardness measurements. The results of the investigations carried out confirmed the possibility of remelting sprayed coatings and obtaining layers free from faults and imperfections typical of plasma spraying. The micro-and x-ray structural examinations revealed, among other things, a significant reduction of porosity (both open and closed ones), homogenization of the chemical composition, smoothing of the surface, and the improvement of coating adhesion to the substrate. The present study is a continuation of the investigations carried out on thermally sprayed and micro-plasma remelted oxide layers, that were started at the beginning of the 1990s at the Material Engineering Institute of the Technical University of Częstochowa. 169

Influence of processing conditions on the properties of thermal sprayed coating: a review

“…It decreases the roughness as well as porosity and increase the adhesion strength of the coatings. Its cost is less than laser remelting but the control of position & heat is cumbersome in this process [173][174][175].…”

Review of Functionally Graded Thermal Sprayed Coatings

“…The remelting of coatings can be carried out using: laser beam [140,141], electron beam [142,143], and, electric arc [144,145]. The laser treatment that is most frequently used is described in detail in [146].…”