Surface quality investigation of turbine blade steels for turning process

The quality of surface or surface finish is the widely used index of product quality and it is also critical in functional behavior of the products like turbine blades, especially when they are in contact with other medium or the materials. This paper presents the surface quality evaluation of turbine blade steels (ST 174PH, ST 12TE and ST T1/13W) for different combination of cutting parameters viz. speed, feed and depth of cut in a CNC turning process. The response surface method (RSM) is devised in design of experiments and 20 experiments per material are conducted in surface quality evaluation and analysis. The results are analyzed using ANOVA and different graphical methods like contour plot and 3D surface graphs. The reasons for the highest surface roughness of ST 174PH material are analyzed using metallurgical perspective. The regression equations for predicting the surface roughness of the materials are formulated in terms of cutting parameters based on experimental results and are verified using confirmatory experiments.

► Three commercial turbine blade steels are considered.
► Surface quality is evaluated for different combination of cutting parameters.
► The metallurgical interpretations for the higher hardness are analyzed.
► The results are analyzed using surface graphs, contour plot and interaction plots.
► Confirmatory experiments are conducted to validate the regression equations.