Thermionic vacuum arc and plasma spray processing of high temperature resistant coatings

A combined coating technology was developed using thermionic vacuum arc (TVA) method for deposition of Re and Re-Ni-Cr films (1) followed by plasma spray of Ni-5Mo-5Al or Al2O3 powders at high velocity and high temperature. The composite multilayered films were developed in order to protect turbine blade material (Nimonic 80 super-alloy) against high-temperature oxidation. The pure TVA metal plasma was monitored and diagnosed using optical emission spectroscopy, the prepared films being characterized before and after oxidation by scanning electron microscopy (SEM), electron dispersive spectrometry (EDS), X-ray diffraction (XRD), gravimetric thermal analysis (GTA) and differential thermal analysis (DTA).