Surface RoughnessOptimization inMachining of N-155 Iron-Nickel-Base Superalloy Using theTaguchiMethod

Due to the properties such as high strength at elevated temperatures and good corrosion and fatigue resistance, superalloys are widely used in industrial applications where such properties are required. These applications include aerospace, steam turbine power plants and petrochemical and nuclear industries. On the other hand superalloys are classified as difficult-tomachine materials owing to their retention of high strength at elevated temperatures, rapid work hardening during machining, presence of hard particles, low thermal conductivity and tendency to make built-up edge on the cutting tool. There is hardly any published paper on machining of iron-nickel-base superalloys despite their industrial importance. In this work, the effects of cutting speed, feed rate and depth of cut on surface roughness in turning of N-155 iron-nickel-base superalloy, were evaluated. Experiments were conducted according to L9 Taguchi standard orthogonal array by using coated carbide cutting tools. By the help of signal-to-noise (S/N) quality characteristic and statistical analysis of variance (ANOVA), optimal cutting parameters and statistical significant level of each parameter were determined. Results showed that feed rate and cutting speed were the most effective parameters on Ra and Rmax, respectively. Additionally, optimum cutting conditions for minimum surface roughness were predicted. Finally, the obtained optimum cutting parameters were verified by a confirmation test.