Previous research confirmed that Pt addition induced a prominent refinement effect of CrN coating, resulting in an enhanced conductivity and corrosion resistance. In this work, a detailed finite element simulation and scratch test were employed to calculate and characterize the fracture failure behaviors (stress distribution, crack damage process, critical coating load, and coating–substrate adhesion energy) of CrN coatings with different Pt contents. Simulation results showed that the synergistic action of dynamic scratch load and extrusion load induced the fracture of the coatings. S11 and S22 caused transverse cracks in the CrN coating, S11 caused longitudinal cracks in the CrN-Pt coating and CrN-3Pt coatings, S22 led to the inclined propagation of cracks in these coatings, and S11 and S22 jointly induced the separation of the coating from the substrate. The doping Pt element in the CrN coating will make the coating easier to fracture and reduce the adhesion strength between the coating and substrate. Scratch test results revealed that adding Pt into the CrN coating will make this coating easier to fracture and cause more serious damage; the simulation results are in good accordance with the scratch test characterizations. The current founding provided a comprehensive understanding for the fracture damage mechanism of Pt-doped nitride coatings.

This study investigated the potential effect of vacuum annealing on the microstructure and hot salt corrosion behavior of CoNiCrAlY/YSZ/LaMgAl₁₁O₁₉ (LMA) double-ceramic coatings. A hot-salt corrosion test revealed that sprayed coatings exhibited an unsatisfactory anti-corrosion performance, and the LMA layer underwent severe fracture and corrosion degradation. Vacuum annealing induced a prominent recrystallization of the amorphous phase in LMA layer, triggering severe volume shrinkage and microcrack initiation. The recrystallization and volume shrinkage of the LMA layer were aggravated by an increase in the annealing temperature. The annealed coating with a higher fraction of the LaMA phase showed superior resistance to hot-salt corrosion. However, the salt mixture diffused simultaneously along the microcracks and eventually eroded into the YSZ layer. These results confirmed that vacuum annealing significantly enhanced the hot-salt corrosion resistance of the LMA layer. However, it deteriorated the barrier effect of the salt mixture through microcrack formation.

A promising ion-beam-assisted deposition (IBAD) method was developed to improve the salt-water corrosion resistance of NiCoCrAlY-AlSiY coating. During hot salt-water exposure, hydrochloric acid (HCl) was produced when chloride salt, water, and metal oxide reacted with each other, while HCl was also produced when chlorine reacted with water. The as-deposited AlSiY layer exhibited a loose texture accompanied by numerous pore defects, which triggered the multi-scale diffusion of HCl, resulting in the large-area corrosion degradation of the coating texture and the rapid diffusion of the NiCoCrAlY bonding layer. By contrast, the ion-beam-assisted AlSiY layer showed a dense texture that effectively inhibited the inner diffusion of HCl and suppressed the corrosion reactions as well as the diffusion of the NiCoCrAlY bonding layer. The current results confirmed the significant potential of IBAD in inhibiting corrosion damage and diffusion of thermal protective coatings.

The effect of a chromium (Cr) transition layer on the hot-salt corrosion behavior of an AlSi alloy coating was studied. Hot-salt corrosion experiments were performed at 650 °C and corrosion kinetic curves were plotted. The weight gain of the AlSi-coated samples increased to 0.89 mg/cm² at 100 h and then decreased steadily to 0.77 mg/cm² at 200 h. The weight of the AlSi-coated samples with the addition of a Cr transition layer increased immediately to 0.79 mg/cm² at 20 h and then gradually increased to 0.85 mg/cm² at 200 h. This Cr diffusion promoted the preferential creation of an Al₂O₃ layer, which effectively hindered the upward diffusion of Fe and also resulted in the production of a Cr₂O₃-SiO₂ layer, which impeded the multi-scale salt mixture’s penetration. The Cr diffusion also caused a notable seal-healing effect, which healed the micro-pores. These oxidation and degradation reactions were considerably repressed by the high barrier properties of these oxide layers and the dense surface, resulting in the increased hot-salt corrosion resistance of the AlSi alloy coating. The current findings provide a feasible strategy for the design of a diffusion barrier layer of a thermal protective coating on martensitic stainless steel.