Investigation of the effect of misorientation grain growth on the creep behavior of nickel-based GTD111DS superalloy

The aim of this study was to investigate the creep behaviour of GTD111 nickel base superalloy produced by directional solidification method. First, a cluster of cylinders of this alloy were cast by Bridgman method. Then, by preparing the tensile specimens, they were subjected to creep test at 870˚C and different stresses. Creep behaviour and microstructural changes of this alloy were measured and evaluated by various tests. Considering that the aim of this project is to identify the creep behaviour in the condition that the grains deviate from the ideal angle during directional solidification, first the grain structure was determined in casting samples, then their mechanical behaviour was investigated by determining the grain deviation. Also, numerical simulation was used to model the grain size of the cast samples. By three-dimensional modelling of grains in creep specimens and then changing the growth angle of dendrites in each grain, numerical analysis of the creep of the specimen using Norton equation and changes in creep life by changing the deflection angle of the grains was obtained. The results showed that increasing the angle of deviation during the growth in a grain from zero to 3 degrees caused a 0.4% increase in mean stress and increasing the growth angle in the same grain from 3 to 10 degrees, caused a 5% increase and an increase from 10 to 20 degrees caused an 11% increase in mean stress in this grain in the middle section of the sample.