Machinability of Stainless Steels : Tool Wear Investigation

Sammanfattning

Machining plays a critical role in manufacturing industries to ensure high-quality products. Therefore, understanding the machinability of different materials is crucial, as it is significantly influenced by material properties. Stainless steels are widely used owing to excellent material properties such as corrosion resistance, high strength, good ductility, etc. However, stainless steels include machining challenges due to material properties such as work hardening, lower thermal conductivity, hardness, and alloying content. This study investigates the machinability of austenitic, martensitic, and ferritic stainless steels in terms of tool wear, tool performance, and applicability of the Colding tool life model under different cutting conditions. For this purpose, longitudinal turning tests at various cutting conditions were conducted for all stainless steel grades. Cutting tools were analysed by light optical microscope, and tool life results were used to calibrate the Colding tool life models. The results indicate that at the same cutting conditions, tool wear and tool performance significantly vary depending on workpiece materials. Martensitic and ferritic stainless steels showed consistent tool wear behaviour, flank wear, and notch wear, respectively. Furthermore, austenitic stainless steel exhibited varying tool wear at different cutting conditions. Additionally, martensitic and austenitic stainless steels achieved the longest tool life at 180 m/min cutting speed and 0.11 mm equivalent chip thickness, while ferritic stainless steel achieved the longest tool life at 170 m/min cutting speed and 0.193 mm equivalent chip thickness. The Colding tool life model recommended the highest cutting speed for martensitic stainless steel at equivalent chip thickness values lower than 0.3 mm but reversed this trend at equivalent chip thickness values higher than 0.3 mm. In addition, the Colding model demonstrated the highest accuracy (1.69%) for martensitic stainless steel.