•The oxidation resistance of CVD Ti(C,N,O) coating is inferior.•The thermal stability of CVD Ti(C,N,O) coating is improved.•The oxidation behavior of Ti(C,N) and Ti(C,N,O) coatings was explained.•High tensile stress of CVD Ti(C,N,O) is harmful to the oxidation resistance.Ti0.51C0.24N0.25 and Ti0.51C0.26N0.21O0.02 coatings were deposited by medium temperature chemical vapor deposition, their oxidation resistance and thermal stability at 600 °C were compared. Ti(C,N,O) coating is oxidized faster than Ti(C,N) coating. The oxidation resistance of Ti(C,N,O) coating is impaired not only by the existence of more pores, fissures and cracks in the oxide layer, but also by lower interfacial adhesion. Higher tensile stress has a negative impact on the oxidation resistance of Ti(C,N,O) coating. It promotes the formation and development of more defects and cracks during cyclic oxidation, it is also harmful to the interfacial adhesion. Although the oxidation resistance of Ti(C,N,O) coating is inferior, the thermal stability is improved. The incorporation of oxygen slows down the phase transformation of Ti(C,N,O) at 600 °C. During the annealing, the hardness of Ti(C,N,O) coating is always higher than that of Ti(C,N).

The microstructural evolution and mechanical properties of S31042 heat-resistant steel after crept at 923 K were systematically investigated. Results show that secondary NbCrN and M23C6 are the predominant precipitates during creep. Long-term creep results in the precipitation of a small amount of σ phase and a few Cr3Ni2SiX. Secondary NbCrN is the most important strengthening precipitate of S31042 steel. At least 75% of the precipitation hardening results from secondary NbCrN. Furthermore, secondary NbCrN is the main factor to affect the variation of hardness of S31042 steel during creep. The dramatic degradation of plasticity is mainly caused by the precipitation of M23C6 at the grain boundaries. Chain-like M23C6, cuboids M23C6 and undissolved NbCrN are also harmful to the creep plasticity of S31042 steel.

This work aims to understand the effect of 1 at.% Y addition on cathodic arc evaporated Ti0.45Al0.55N coating. Ti0.45Al0.55N coating and Ti0.45Al0.54Y0.01N coating were deposited on WC-Co substrate by cathodic arc evaporation method, and their microstructure and properties were compared. The addition of 1 at.% Y does not change the crystalline phase of Ti0.45Al0.55N coating. It still consists of (Ti,Al)N phase with a cubic NaCl-type structure. However, addition of Y leads to reduction of columnar structure and refinement of grains. Compared with Ti0.45Al0.55N coating, the hardness of Ti0.45Al0.54Y0.01N increases by 24%. The residual stress of Ti0.45Al0.54Y0.01N coating is approximately three times that of Ti0.45Al0.55N coating. Ti0.45Al0.54Y0.01N coating exhibits superior oxidation resistance, owing to the retardation of oxide layer growth, the dense fine-grained structure and the improved oxide layer adhesion.Highlights► The addition of Y does not change the crystalline phase of Ti0.45Al0.55N. ► The hardness of Ti0.45Al0.54Y0.01N increases by 24%. ► The oxidation resistance of Ti0.45Al0.54Y0.01N coating is superior to Ti0.45Al0.55N. ► We explained why the oxidation resistance of Ti0.45Al0.54Y0.01N coating is improved.

In order to optimize the precipitation strengthening of S30432 heat-resistant steel, the evolution and strengthening mechanisms of Nb(C,N), M23C6, and Cu-rich particles during short-term aging at 923 K were discussed, more emphasis was put on Cu-rich particles. It is Cu-rich particles, rather than Nb(C,N) or M23C6, that play the most important role in the strength of S30432 steel. At least 60% of the yield strength results from the precipitation hardening of Cu-rich particles. Furthermore, Cu-rich particle is the main factor to affect the variation of the strength of S30432 steel during short-term aging. When Cu-rich particles are smaller than 6 nm in diameter, cutting mechanism is dominant. After Cu-rich particles exceed 6 nm, Orowan bypass mechanism governs. The tendency of the calculated yield strength attributed to Cu-rich particles with aging time is in good agreement with experimental result.Highlights► Cu-rich particles, rather than Nb(C,N) or M23C6, play the most important role. ► At least 60% of the yield strength results from Cu-rich particles. ► When Cu-rich particles are smaller than 6 nm, cutting mechanism is dominant. ► After Cu-rich particles exceed 6 nm, Orowan bypass mechanism governs. ► The tendency of calculated strength is in good agreement with experimental result.

Good oxidation resistance of hard coatings is important for cutting tools. Ti0.5Al0.5N coating and Ti0.5Al0.4Si0.1N coating were deposited by cathodic arc evaporation and their oxidation behavior at 850 °C, 900 °C and 1000 °C was compared. The effect of Si addition on the oxidation resistance of Ti0.5Al0.4Si0.1N was investigated. Results show that the oxidation resistance of Ti0.5Al0.4Si0.1N coating at 850–1000 °C is superior to Ti0.5Al0.5N coating. The improved oxidation resistance of Ti0.5Al0.4Si0.1N coating can be ascribed to the combined action of Al2O3 and SiO2 barrier layer, the reduction of columnar structure and the refinement of grains. In particular, Si addition increases the diffusion coefficient of Al and promotes the preferential formation of Al2O3 barrier layer.Highlights► The oxidation resistance of Ti0.5Al0.4Si0.1N coating at 850–1000 °C is superior to Ti0.5Al0.5N coating. ► Si addition increases the diffusion coefficient of Al. ► Si addition promotes the formation of Al2O3 and SiO2 barrier layer. ► Si addition stimulates the reduction of columnar structure and the refinement of grains.