INFLUENCE OF DIE FORGING PARAMETERS ON THE MICROSTRUCTURE AND PHASE COMPOSITION OF INCONEL 718 ALLOY

The object of the present investigation was Inconel 718 alloy. The material in the initial state and after forging at the temperatures of 1100 degrees C and 1000 degrees C was examined. Diffraction analyses indicate that a nickel-based gamma solid solution is a dominating phase in the alloy (so-called nickel austenite). Apart from a gamma solid solution, which constitutes the matrix, certain volume fractions of the other phase were detected e.g. delta phase and carbides. It was found that, due to thermo-mechanical-treatment at both temperatures, the phase composition of Inconel 718 was considerably changed in comparison to the initial state. On the contrary, differences in the temperature of forging did not significantly influence the alloy constitution. However, both of the temperatures of forging result in distinct texture intensity. Microstructure observations indicate that forging at 1000 degrees C led to recrystallization by creation of the new recrystallizated grains near or on the grain boundaries of existing deformed grains. After forging at 1100 degrees C, the microstructure was fully recrystallized at the whole volume of the material.