Laser remelting of Ni-Cr-Re plasma spraying coating

Abstract

The plasma spray technology allows spraying a wide variety of materials. Atmospheric plasma spraying (APS) consists in injecting a powder feedstock material in a plasma jet to melt and accelerate the injected particles and spray them onto a substrate. The coating growth is thus realized by the impingement and spreading of sprayed particles. This mechanism of coating formation induces the presence of pores and micro-cracks. In order to eliminate those drawbacks, laser remleting may be used to improve the properties and performances of plasma sprayed coatings. In the present paper, the Ni20%C + 20%Re coating fabricated by plasma spraying on stainless steel substrate were remelted by CO2 laser, and the effect of laser remelting on microstructure and hardness of plasma sprayed Ni20%Cr + 20%Re coating were studied. The microstructure of plasma sprayed and laser remelted coatings were analyzed using scanning election microscopy (SEM) and energy disperse spectroscopy (EDS). The micro-hardness of coating was measured using micro-hardness tester. The results show that the laser remelted coating becomes much denser moreover, the chemical composition of the coatings becomes homogeneous