Abstract
In this study, surface roughness, tool wear and cutting force have been investigated in milling of Böhler K390 cold work tool steel with coated carbide inserts. Test specimens were tempered at different three temperatures after quenching. Milling tests were performed at four different cutting speeds and feed rates. Surface roughness R_a and cutting forces were measured for further evaluation. Besides, images of cutting inserts were taken from electron microscope (SEM) for determining the wear types and mechanism. Analysis of variance (ANOVA) was used to determine the most influencing cutting parameters on the milling performance. According to the experimental results, they have been low cutting force, value of R_a (0.031 μm), and minimum tool wear in a specimen tempered at high temperature. Due to intermitted cutting, pressure and high temperature, there are more chipping and attrition on cutting insert. Surface qualities of milling surfaces were obtained by grinding operations. According to the analysis of variance feed rate levels, the most effective parameters are R_a and F_m.

Key words
hard milling, cutting force, tool wear, surface roughness, powder metallurgical steel

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