White layer formation and hardening effects in hard turning of H13 tool steel with CrTiAlN and CrTiAlN/MoST-coated carbide tools

White layers are hard, brittle and normally associated with a tensile stress and hence the ability to reduce the fatigue life of machined components. Several authors have reported the formation of white layers on components after turning processes by using CBN/PCBN and ceramic cutting tools. However, there are hardly any studies that have reported on white layer formation for new and low-cost-coated carbides. The study in this paper was conducted to determine the effect of CrTiAlN and CrTiAlN+MoST and high cutting speeds on white layer formation in machining tool steel. H13 tool steel (57 HRC) was examined after turning at a conventional and high cutting speed. Coated tools resulted in lower workpiece and tool temperatures. Hence coated tools resulted in reduced and also more homogeneous hardening effects compared to the uncoated tool. In addition, the higher cutting speed produced negligible white layers. Thus, the paper elucidates on the benefits of coatings on surface hardening in conventional and high speed machining.     

Size effect and tool geometry in micromilling of tool steel

The market for freeform and high quality microdies and moulds made of steel is predicted to experience a phenomenal growth in line with the demand for microsystems. However, micromachining of hardened steel is a challenge due to unpredictable tool life and likely differences in process mechanism compared to macro-scale machining. This paper presents an investigation of the size effect in micromilling of H13 hardened tool steel. In this case, the size effect in micromilling hardened tool steel was observed by studying the effect of the ratio of undeformed chip thickness to the cutting edge radius on process performance. The paper explores how this ratio drives the specific cutting force, surface finish and burr formation in micro-scale machining. In addition, the effect of different microend mill geometry on product quality was explored. The paper provides a valuable insight into optimum micro-scale machining conditions for obtaining the best surface finish and minimizing burr size.     

Experimental investigation of shot peening: correlation of pressure and shot velocity to Almen intensity

The International Journal of Advanced Manufacturing Technology - Shot peening is a mechanical surface enhancement process that is extensively used in various industries to increase fatigue life of...