Hard milling of hardened steel has wide application in mould and die industries. However, milling induced surface finish has received little attention. An experimental investigation is conducted to comprehensively characterize the surface roughness of AISI D2 hardened steel (58-62 HRC) in end milling operation using TiAlN/AlCrN multilayer coated carbide. Surface roughness (Ra) was examined at different cutting speed (v) and radial depth of cut (dr) while the measurement was taken in feed speed, Vf and cutting speed, Vc directions. The experimental results show that the milled surface is anisotropic in nature. Surface roughness values in feed speed direction do not appear to correspond to any definite pattern in relation to cutting speed, while it increases with radial depth-of-cut within the range 0.13-0.24 µm. In cutting speed direction, surface roughness value decreases in the high speed range, while it increases in the high radial depth of cut. Radial depth of cut is the most influencing parameter in surface roughness followed by cutting speed.

This paper presents the results of experimental investigation conducted on a vertical machining centre (VMC) to ascertain the effectiveness of TiAlN/AlCrN multilayer coated carbide inserts in end milling of AISI D2 hardened steel (58-62 HRC) In high-speed dry hard milling, different cutting speed (v) and radial depth of cut (dr) were applied. Tool failure modes and wear mechanisms were examined at various cutting parameters. Flank wear, chipping and breakage at cutting edge were found to be the predominant tool failure for the cutting tools. Built-up edge, adhesion and abrasive are the wear mechanisms observed on the cutting tools. The highest volume of material removed, VMR attained was 1500 mm3, meanwhile the highest tool life (T) was 4.97 min. The surface roughness, Ra values from 0.20 to 0.45 μm can be attained in the workpiece with a high volume material removed. The relationship of tool wear performance and surface integrity was established to lead an optimum parameter in order to have high volume material removed, maximum tool life as well as acceptable surface finish.

Surface topography plays an important part in understanding the nature of machined surfaces. This study is focused on surface topography of AISI D2 hardened steel (58-62 HRC) under dry milling process. Roughness, surface morphology and defects analysis were investigated. This study achieved R a in range of 0.18 to 0.30 µm which is acceptable in mould and die requirement. Moreover, surface roughness decreased as cutting speed increased. From the optical microscope observation shows that the milled surface is anisotropic in nature. The lay pattern is produced by the combination of tool movement during milling operation (cutting and feed speed directions). Meanwhile, the AFM images indicated that the milled surfaces are groovy constructed by low-amplitude topography (between peak and valley of the machined surface waves). Surface defects were found in this study were debris, groove and cavity, all of which affected the surface roughness value.

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