In this work, 2 at% Mo, 2 at% Nb and 2 at% Hf were substituted for the same amount of W into a Co-9Al-9W-2Ta-0.02B alloy (hereafter referred as to 2Mo, 2Nb and 2Hf alloys, respectively, while the original alloy is denoted as 0Me alloy). The effect of the Mo, Hf and Nb additions on the isothermal oxidation resistance, oxide scale evolution and failure mechanism, of the Co-9Al-9W-2Ta-0.02B alloy when exposed at 800 °C and 900 °C for 100 h was investigated. It was found the Mo, Hf and Nb additions degraded the oxidation resistance of the Co-9Al-9W-2Ta-0.02B alloy, while the 2Mo alloy always displayed the poorest oxidation resistance, resulted from heavy spallation of the oxide scale. An oxide scale composed of an outer Co3O4+CoO layer, a middle complex oxide layer enriched with Al, W and Ta, and a γ/needle-like Co3W zone adhering to the γ/γ' substrate was gradually formed; moreover, a continuous or discontinuous Al2O3 layer and dispersive Al2O3 dots or slices were observed within the γ/needle-like Co3W zone, depending on the oxidation temperature and added elements (Mo, Hf and Nb). The formation of volatile MoO3 in the oxide scale of the 2Mo alloy enhance the exfoliation of the oxide products, resulting in severe spallation and poor oxidation resistance

The creep behavior and microstructure of a Ni3Al base single crystal alloy IC6SX with [001] orientation under the testing conditions of 760°C/593MPa, 980°C/205MPa, and 1100°C/75MPa were investigated. The experimental results showed that Alloy IC6SX had good creep resistance and its creep resistance at elevated temperatures was similar to the second generation nickel-base single crystal alloy containing Re. TEM analysis indicated that the dislocation configuration and movement pattern were different under different temperature and stress conditions. It has been found that under the test condition of 1070°C/137MPa the dislocations moved within the γ channel during the primary creep stage, and the motion of dislocations were prevented by the matrix of γ′ phase, which reduced the creep rate of the alloy. In the secondary creep stage, dislocations cut into the γ′ phase from the γ/γ′ interface. However in the third creep stage, the dislocation pileups were observed in both γ and γ′ phase, and dislocation multiplication occurred when the dislocations with different Burgers vector met and reacted each other

The hot corrosion behavior of nickel-based single-crystal superalloy after drilling is investigated at 900 °C. The characteristics of hot corrosion after drilling which are different from normal hot corrosion are reflected in the formation of a more stable oxide layer and less severe spallation. The change of microstructure around the hole is the main reason for the formation of a stable oxide layer during hot corrosion by changing the diffusion process of alloying elements. Subsequently, the formation of a stable oxide layer can reduce the effect of spalling by optimizing surface stress.

A study is carried out on the effect of different surface native pre-oxides on hot corrosion of single crystal nickel-based superalloy at 900 °C. The effect of different oxides formed by different superalloys through pre-oxidation on hot corrosion is verified by normal hot corrosion and tube sealing experiments. The relationship between different surface oxides and the effect of different surface oxides layer on the hot corrosion properties of alloys are studied. In summary, the stable and dense surface pre-Al₂O₃ layer which can be obtained by pre-oxidation has an obvious positive effect on the improvement of superalloy hot corrosion resistance in reaction. In addition, the internal sulfides are analyzed in depth, and the relationship between Cr, Mo, O and S is discussed in detail.

With the complexity of the structure of aero-engine turbine blades, the blade wall thickness continues to decrease. It is found that when the blade wall thickness decreases to a certain extent, its mechanical properties will decline significantly. It is extremely important to study this phenomenon of a significant decline in mechanical properties caused by wall thickness. In this paper, the creep behavior of a second-generation Ni₃Al-based single crystal superalloy with different wall thicknesses and [001] orientation at 980 °C/220 MPa has been studied and compared with the creep life of Φ4 round bar. The experimental results show that the second orientation and the surface affected zone are not the main reasons for the reduction of the life of thin-walled samples under this experimental condition. By analyzing the fracture morphology and deformed microstructure of thin-walled samples with different thicknesses, it is found that the thickness debit effect of the single crystal alloy occurs since the effective stress area of the alloy changes due to internal defects and surface affected zone during the creep process. For thicker samples, the creep life of the alloy can be extended by making the samples undergo certain plastic deformation through better plastic deformation coordination ability, while for thinner samples, the plastic coordination ability is poor, and the ability to extend the creep life through plastic deformation is also weaker when the effective stress area of the alloy changes, which leads to the thinner samples being more prone to fracture.