Simultaneous Optimization of Machining Parameters for Dimensional Instability Control in Aero Gas Turbine Components Made of Inconel 718 Alloy

Aero gas turbine components made of Inconel 718 superalloy revealed significant dimensional instability after machining. The dimensional instability is a manifestation of alterations in residual stresses and microstructure, which are influenced by machining parameters. This paper presents a simultaneous optimization technique used to control the dimensional instability in turning operation. Empirical equations are established for predicting surface residual stresses, surface finish, dimensional instability and tool life using response surface methodology. Experimental results show a strong correlation between residual stresses and dimensional instability. A desirability function approach is used to optimize the multiple responses and machining parameters are derived for practical applications. Inconel 718 test specimen and jet engine components machined with optimal cutting parameters show dimensional instability within the acceptable tolerance band. [S1087-1357(00)01704-4]