Abstract
Single crystal Ni based superalloys for Gas Turbine blades has an interesting structure that the L12 γ' phase cubes are regularly arranged at equal intervals in the face center cubic γ phase. During the high temperature creep test, the γ' phase of Ni based superalloys has multiple cubes in the transition region. However, the γ' cubes begin to connect with one another in the lateral direction perpendicular to the tensile direction to be rafting structures in the steady state region and the accelerating region. The multi scale simulation methods including the three dimensional phase field method are well-known as simulation methods for phase changes. However, it is convenient to have a simulation method for metallographic changes using various metallographic charts in published papers and data bases, because the published metallographic charts can be utilized for prediction of the behavior between the charts before and after phase transition. Therefore, in this research, Metallographic changes of CMSX-4 which is a single crystal Ni based superalloy in the accelerating region were studied by using metallographic charts of Miura, Kondo and Matsuo's paper via the two dimensional discrete cosine transform (2D-DCT) and the Maximum Entropy Method. As a result, it has been found out that this method could be a promising method to study metallographic changes coming up with the creep rate changes.
