High temperature oxidation behavior and oxide film properties of IN718 alloy after heat treatment by hot pressing sintering

Abstract

The IN718 superalloy was prepared by hot pressing sintering method, and the IN718 alloy blocks under different sintering pressures were obtained. The hot-pressed IN718 superalloy(HPS IN718) prepared by the optimum sintering pressure was treated by solid solution and aging. The high temperature oxidation behavior and the properties of oxide film of HPS IN718 at 850 °C in air were studied. The microstructure of HPS IN718 was characterized by optical microscope(OM), X-ray diffractometer(XRD), scanning electron microscope(SEM), and energy dispersive spectrometer(EDS). The morphology and microstructure of the oxide film of HPS IN718 at 850 °C for different oxidation times were analyzed. The adhesion and wear resistance of the oxide film was tested by an automatic scratch tester and a pin-on-disc friction and wear tester. The results show that the IN718 alloy prepared by sintering pressure 30MPa has good density, and more uniform structure. The results of the oxidation test show that with the increase in oxidation time, the weight of the sample increases parabolically. The oxidation rate was 3.84×10-3 mg/(cm2·h1), which belongs to the complete oxidation resistance level. The oxides gradually aggregate and grow from small particles and clusters in the early stage of oxidation. After 125h oxidation, the thickness of the oxide layer is 3~4 μm. The outermost layer of the oxide film is composed of TiO2, Fe2Cr2O4, and Fe0.7Cr1.3O3, the subsurface layer is dense Cr2O3, and the inner oxide is Al2O3. As the oxidation time increases, the adhesion between the oxide film and the substrate increases. The surface friction coefficient of the sample is reduced. It is found that after oxidation for 125h, the adhesion between the oxide film and the substrate is 15N, the surface friction coefficient is 0.08, the friction coefficient is reduced by 0.37 compared with the substrate, and the wear resistance is the better.