Interlayer effect on the characterization of the La-Cr-O coatings with post-sputtering annealing treatment

In this study, the deposition of La-Cr-O coatings on AISI 316 stainless steel was conducted by using a DC magnetron sputtering process. Three types of La-Cr-O coatings were designed, one type without interlayer, and another two types with an interlayer of Cr and CrN film, separately. This study aims to explore the interlayer effect on the properties of La-Cr-O coatings after post-annealing treatment. The coatings were characterized using the X-ray diffractionmeter (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and thermal gravimetric analysis (TGA)/differential scanning calorimetry (DSC).The results showed that the three as-deposited La-Cr-O coatings had an amorphous structure. After annealing at 800 °C for 1 h in the air, the structure was transformed to the LaCrO₃ perovskite phase. Compared with the coatings without an interlayer, the double-layered coatings did not show the Cr₂O₃ phase in the structure. It implies that the use of the interlayer in the coatings could efficiently prohibit the diffusion of Cr to form oxide on the out-layer. Based on the TGA/DSC analysis and the electrical resistance measurement, it is understood that the annealed La-Cr-O coating with the CrN interlayer turns in the best performance in both chemical stability at high temperature and electrical resistance.