The failure of plasma-sprayed thermal barrier coatings (TBCs) during service is usually related to the cracking behavior. In this study, plasma-sprayed TBCs were prepared with two kinds of agglomerated sintered yttria-stabilized zirconia (YSZ) powders with different particle sizes. The evolution of mechanical properties and crack propagation behavior of the coatings during the whole life stage were studied by a thermal shock test. The effect of powder particle size on the cracking behavior of the TBCs during thermal shock was analyzed from the aspect of pore structure, mechanical properties, and stress state of the coatings. The crack propagation and coalescence in the direction parallel to the substrate in the coating is the main factor leading to the spalling failure of the coating during thermal shock. Although the coating prepared by fine YSZ has higher fracture toughness, the lower strain tolerance will increase the cracking driving force on the crack tip of the coating during thermal shock, and the cracks in the coating propagate merge at a faster rate during thermal shock. The larger porosity and pore size of the coating prepared by coarse YSZ help the coating suffer less thermal stress during thermal shock. Although the existence of pores reduces the fracture toughness of the coating to a certain extent, the increase of strain tolerance reduces the crack growth rate in the coating, so the coating has a longer life.

CoNiCrAlY coatings are widely used as typical high-temperature materials to enhance the surface performances of nickel-based superalloy materials, which can be used as bond coats in thermal barrier coatings and abradable seal coatings. In this study, high-pressure cold spray technology was used to deposit CoNiCrAlY coatings on nickel-based superalloy substrates. The microstructure characteristics and oxidation behaviors of CoNiCrAlY coatings prepared by different gas types and cold spray parameters were systematically investigated. EBSD analysis showed that the deformation of the helium coating was more distinct, and the grain size of the coating fabricated by helium was smaller than that by nitrogen as seen from the grain morphology. The high-temperature oxidation results showed that the coating oxide film thickness varied parabolically with time for both coatings after 500 h isothermal oxidation at 800 °C, 900 °C, and 1000 °C, and the oxidation rate of the coating after heat treatment was lower than that of the as-sprayed coating. In addition, the shrinkage of the aluminum reservoir inside the coating, the element diffusion rate, and the amount and type of oxide generation on the surface all affected the oxidation process. Additionally, the helium coating had a lower oxidation growth rate and better oxidation resistance. Therefore, cold spray can be an alternative way to fabricate high-quality CoNiCrAlY coatings.

In this study, copper–titanium (Cu-Ti) composite coatings with 6 wt.% titanium content were fabricated via cold spray additive manufacturing (CSAM) using nitrogen as the propellant gas. The synergistic effects of propellant gas temperatures (600 °C, 700 °C, 800 °C) and post-heat treatment temperatures (350 °C, 380 °C, 400 °C) on the microstructure and tensile properties were systematically investigated. Tensile testing, microhardness characterization, and fractography analysis revealed that increasing the propellant gas temperature significantly enhanced the plastic deformation of copper particles, leading to simultaneous improvements in deposit density and interfacial bonding strength. The as-sprayed specimen prepared at 800 °C propellant gas temperature exhibited a tensile strength of 338 MPa, representing a 69% increase over the 600 °C specimen. Post-heat treatment effectively eliminated the work-hardening effects induced by cold spraying, with the 400 °C treated material achieving an elongation of 15% while maintaining tensile strength above 270 MPa. Microstructural analysis demonstrated that high propellant gas temperatures (800 °C) promoted the formation of dense lamellar stacking structures in copper particles, which, combined with a recrystallized fine-grained microstructure induced by 400 °C heat treatment, enabled synergistic optimization of strength and ductility. This work provides critical experimental insights for process optimization in CSAM-fabricated Cu-Ti composites.