Enhanced ablation resistance of ZrC–ZrO2 nanocomposite ceramic coating on TiAlNb medium-entropy alloy prepared by a novel strategy

Abstract

A novel one-step liquid plasma-assisted particle deposition and sintering (LPDS) method is used to prepare a ZrC–ZrO2 nanocomposite ceramic coating on a TiAlNb medium-entropy alloy to enhance its ablation resistance. For comparison, a conventional plasma electrolytic oxidation (PEO) ceramic coating is fabricated on a substrate without ZrC particles. Results show that numerous ZrC particles are introduced into the coating, accompanied by partial oxidation to ZrO2 during the LPDS. The thickness of the nanocomposite coating increases significantly by approximately 11.4 times compared with that of the PEO coating. At 1000 °C, the ablation thickening of the ZrC–ZrO2 nanocomposite coating is approximately 1/4 of that of the substrate after ablation in air. Moreover, 17.88% and 2.83% of the substrate surface and PEO coating are peeled, respectively, whereas no peeling occurred in the ZrC–ZrO2 nanocomposite coating. This can be attributed to the high melting point and exceptional toughness of ZrO2, which allow it to absorb the stress caused by thermal shocks and inhibit crack formation. A thick nanocomposite coating is crucial for protecting the substrate by preventing oxygen from permeating the coating and oxidizing the substrate. Additionally, the glass phase of SiO2 densifies the pores and cracks in the coating, thereby significantly inhibiting the inward diffusion of oxygen and preventing ablation. Therefore, LPDS is a novel strategy for designing and fabricating multifunctional coatings to enhance the thermal protection of alloy substrates via the incorporation of various functional particles.