Failure mode analysis of carbide cutting tools used for machining titanium alloy

Intensive research on the performance of coated carbide tools in machining titanium alloy is being conducted worldwide. Titanium alloy has special characteristics such as high strength at elevated temperature and high mechanical resistance that makes carbide tools suitable to cut this material. This is because carbide tools are classified as hard and highly resistant to wear even at high temperature. This paper discusses the failure mode of a coated carbide cutting edge that is caused by the loading and unloading effect during milling. Tool failure adversely affects tool life, the quality of the machined surface and the surfaceʹs dimensional accuracy, and consequently the economics of cutting operations. The milling parameters that were observed to affect the failure of coated carbide tools were cutting speed, feed rate, depth of cut, and the application of a cutting fluid. Wear occurred along the flank and rake faces, which then propagated into the substrate material after the removal of the coating material. Wear along the flank and rake faces led to the concentration of stress over a certain area of the cutting edge, which was initiated by a microcrack and then propagated due to the loading and unloading effect during the intermittent milling process until significant brittle fracture occurred in the substrate material. Cutting speed and depth of cut were identified as the main factors responsible for the failure and fatigue of the coated carbide tools during the milling of titanium alloy.