This study is aimed at clarifying the change in the surface structure of TiSiN film formed by PVD on Type 304 stainless steel after high-temperature long-term oxidation in air.  The change in the thin film layer structure from the outermost surface to the PVD layer is examined by changing the X-ray penetration depth depending on the incidence angle ω at room temperature for samples oxidized at 1000℃.

The structure analysis of high-temperature oxidized TiSiN film using the low-angle incidence method is performed after heating in air at 1,000℃×30hrs. or 700℃×10hrs. in a muffle furnace and cooling.  The incidence angle ω during measurement is fixed, and the measurement is performed by moving the detector part (2θ).

As a result, it was revealed that in high-temperature oxidation at 1,000°C for 30 hrs., TiO₂ appears on the outermost surface, Cr₂O₃ forms underneath, and Fe₃O₄ is formed in an even lower layer as a result of the Fe contained in the base metal Type304SS diffusing into the coating.  On the other hand, it was also found that in a slightly lower high-temperature environment of 700°C, a strong and dense TiSiN coating is maintained by the formation of β-Si₃N₄.  Oxides such as SiO₂ were not formed on the surface of the coating, but remained as nitride β-Si₃N₄ inside.  Here, it is known that Si has a higher affinity with nitrogen than oxygen, suggesting that SiO₂ was not formed.  It was also confirmed that the surface and its vicinity have a simple film structure that forms TiO₂ and FeO.