Heat treatment of superalloys produced by powder metallurgy method

In this thesis, the production and characterization of novel Ni based Inconel 718 superalloys for aircraft applications were carried out. Ni based Inconel 718 superalloys were produced by traditional powder metallurgy (press-sintering) method. In this thesis, Ni based Inconel 718 superalloy powders were prepared by mechanical alloying (ball mill) method. Then, the green specimens were produced by hydraulic pressing. Then, the green samples were sintered between 1100-1250 °C for 1 hour. Finally, heat treatments were applied to the sintered Ni based Inconel 718 superalloys samples. The sintered specimens were put into solution for 1 hour at 1000 °C and then quenching was applied. Then, the quenched specimens were aged between 400-550 °C. The effects of various alloying elements added to Ni based Inconel 718 superalloys on the properties were investigated. The microstructure of the produced Ni based Inconel 718 superalloys was investigated using destructive (wear test, hardness test) and non-destructive (ultrasonic testing, eddy current test) methods. Additionally, the electrochemical corrosion behaviour of the Ni based Inconel 718 superalloys was investigated in NaCl solution by using open circuit potential, Tafel and electrochemical impedance spectroscopy tests. In addition, high temperature corrosion tests were carred out. Properties of the superalloys were investigated and optimised by ab initio based computational materiaşs science software (CASTEP) and calculated phase diagrams (CALPHAD) based software (Thermo-Calc).