Thermal Expansion of TRIP Steels and Composite Coatings

High-temperature X-ray diffraction is used to study the peculiarities of the thermal expansion of VNS9-Sh (23Kh15N5AM3-Sh) TRIP steel; 20Kh15AN3MD2 steel without the TRIP effect (both steels belong to the Fe–Cr–Ni–Mn system), and multiphase heat-resistant coatings with the compositions c-ZrO₂ + α-Al₂O₃ + γ-Al₂O₃, α-Al₂O₃ + γ-Al₂O₃ + t-ZrO₂, and Si + SiC. The studies are performed at temperatures up to 1000°C. VNS9-Sh steel with a larger lattice parameter of the α phase as compared to that of 20Kh15AN3MD2 steel (2.890–2.892 and 2.888 Å, respectively) is shown to have a lower linear thermal expansion coefficient (LTEC): (7.6–7.9) × 10^–6 and (10.3–10.9) × 10^–6 K^–1, respectively. It is confirmed that high-temperature X-ray diffraction is an efficient method for estimating the LTEC of multiphase coatings and that the single-crystal LTEC characteristics of phases with tetragonal and hexagonal lattices can be estimated on polycrystalline objects. For phases with tetragonal and hexagonal structures, we are the first to use LTEC representation in the form of a second-rank tensor, which allows us to increase the accuracy of estimating LTEC.