Metal Alloy

First principles study on oxidation resistance of alloys

Heat-resistant steel refers to stainless steel materials that can withstand greater stress and have strong surface stability under high temperature conditions above 600 ° C. Austenitic heat-resistant steel has high melting point, high temperature strength and high temperature oxidation resistance, and has been widely used in aviation engines, industrial gas turbines and other fields. Its excellent high temperature oxidation resistance is mainly due to the formation of protective oxide film Cr2O3 and Al2O3 on the alloy surface. Compared with the metal matrix, the oxide film has a higher melting point, and the thermodynamic stability is very good. It can effectively prevent the metal atoms such as Fe in the matrix from spreading to the surface, and at the same time prevent the internal diffusion of O in the external environment, which protects the matrix. Due to the different atomic arrangement, orientation and chemical composition of the two parts of the matrix/oxide film interface, the structure is relatively weak. Under the long-term thermal cycle service environment and external stress, defects are easy to cause the oxide film to fall off, the oxidation resistance is reduced, and serious material failure will be caused and the service life will be shortened. Therefore, exploring and improving the matrix/oxide film interface bonding strength is the most favorable way to improve the oxidation resistance and prolong the service life of heat-resistant steel.

The segregation behavior of alloyed elements Si, Al, V, Ti, Mo, W, Nb, Y at Fe(111)/Cr2O3(0001) interface and its effect on interface bonding ability were systematically analyzed by first-principles calculation method (CASTEP). The results show that W, Mo and Nb tend to segregate at the interface. And Y, Al, Si, Ti, V are not easy to segregate at the interface. By calculating the interface separation work and interface structure characteristics, it is found that Si and Al can improve the interface bonding ability by interacting with O at the interface, that is, improve the bonding of the surface oxide film, and thus indirectly enhance the oxidation resistance.

Comp. Mater. Sci. 109, 293-299 (2015)