| Al, Cr | Stabilizing elements of γ-phase, reducing the alloy density | Forming a dense oxide layer (Al2O3 or Cr2O3) to |
| | prevent the oxidation of alloy |
| Ni | Extending γ/γ' two-phase region, increasing the volume | Inhibiting the formation of the oxide layer Al2O3, |
| fraction of γ' phase | and reducing the oxidation resistance of the alloy |
Ta, W | Stabilizing elements of the γ' phase, significantly increasing the alloy density and forming the new phases unfavorable to mechanical properties with high content | Enhancing the oxidation resistance of the alloy below 1000oC by reducing the diffusion rate of each element, and decreasing the oxidation resistance of the alloy above 1000oC by inhibiting the formation of continuous oxide layers |
Ti | The stabilizing element of γ' phase, significantly reduces the density of the alloy and the mismatch between the two phases of γ/γ' which benefits mechanical properties. However, high content Ti leading to the formation of lamellar TCP phase is not conducive to the mechanical properties | With increasing temperature, the resistance to oxid-ations decreases because of the reduction in the density of oxide films caused by a phase trans-formation in TiO2 |
C, N, B | The alloy's strength increases, but its ductility and toughness decrease, due to the formation of interstitial phases with high hardness, melting point, and brittleness | The addition of small amount of B is good for enhancing the adhesion of oxide film to the substrate, but too much of it will promote the diffusion of the element, which is not good for the high temperature oxidation resistance of the alloy |