Cyclic Oxidation Resistance of In718 Superalloy Treated by Laser Peening

The aim of this study was to improve the cyclic oxidation resistance of In718 superalloy by laser peening(LP). Specimens were treated by LP from one to three times, respectively. The cyclic oxidation tests at 900 degrees C for periods up to 2 h were conducted. Changes of the top surface morphology and microstructure were analyzed by scanning electron microscope (SEM), energy-dispersive spectra (EDS), transmission electron microscope (TEM) and X-ray diffraction technique (XRD), respectively. The weights were measured between the oxidation cycles to assess the oxidation of the specimens. The top surface microstructure after LP was characterized by highly tangled and dense dislocation arrangements and a high amount of twins. Protective oxidation layer was generated more quickly on the surface treated by LP. The average oxidation rate was about 50 % lower. A tiny homogeneous oxidation layer containing (Fe, Cr)(2)O-3, NiCrO3 and Ni(Al, Cr)(2)O-4 spinel was generated on the surface. The experimental results of cyclic oxidation tests show that specimens treated by LP have a better high temperature oxidation resistance, and the antistrip performance of the oxidation layer improves. Moreover, the effects of LP are strengthened with the increase of laser peening.