Cutting Performance And Failure Mechanisms Of A Pure WC Cutting Tool And A SiC-TiC Cutting Tool

In recent years,WC-based cemented carbide is considered to be one of the most proper tool materials for machining metals on account of their combination mechanical properties,including high wear resistance,high heat resistance and high hardness.It has been widely applied in high-speed cutting due to its excellent physical performance,just like good thermal conductivity,low density and low friction coefficient.Most WC-based cemented carbide makes use of Co as binding phase to develop its toughness and density.Whereas,the binding phase will react with the workpiece materials of high chemical activity and reduce the high-temperature behavior of the cutting tools.So the pure WC material without the binding phase may have more opportunities to be used.Meanwhile,SiC-TiC material has a good combination mechanical behavior as a kind of composite material.However,no investigation of the cutting performance and failure mechanisms of pure WC cutting tools and SiC-TiC cutting tols in cutting metals has been reported.In the present paper,the cutting performance,failure modes and mechanisms of the pure WC cutting tool and a SiC-TiC cutting tool were investigated,with an WC/Co/(Ta,Ti)C ceramic tool YW2 as competitors.In the present research,a pure WC tool material and a SiC-TiC tool material were produced by hot pressed sintering,cold isotatic pressing and hot isostatic pressing.And use them as cutting tool materials.The relative density of the cutting tool material was measured by the Archimedes method.The Vickers hardness of the material was measured by a Vickers microhardness machine.The fracture toughness of the material was calculated according to the hardness.The flexural strength was measured through three-point bending test.Dry cutting tests were carried out on a C0618b lathe and investigated its cutting performance.General view of the worn tool face was observed by light optical microscopy.Worn and fractured surfaces of the tools were observed by scanning electron microscopy(SEM)and energy-dispersive X-ray spectroscopy(EDS)to reveal the failure mechanisms.A high attention was paid to the microscopic structure comparison of worn and fractured surfaces of the cutting tools between different workpiece materials,which was used to explain the distinction in wear mechanisms and failure modes.Meanwhile,set a YW2 cutting tool as a competitor.The results of cutting process revealed that the main tool wear types of pure WC cutting tools in dry cutting Cr12Mn5Ni4Mo3Al stainless steels was adhesive wear.Built-up edges were formed in the wear zones and the tool noses were severely worn.Plenty of workpiece materials were adhered to the rake face and flank face.The main tool wear types of SiC-TiC cutting tools in dry cutting Cr12Mn5Ni4Mo3Al stainless steels was adhesive wear.A "blade slot" were formed on the flank face.The tool life of pure WC cutting tools is shorter than that of YW2 and SiC-TiC in cutting Cr12Mn5Ni4Mo3Al stainless steels due to the strong adhesion tendency of steel to the pure WC.The main tool wear type of pure WC cutting tools in dry cutting HT200 grey cast iron was abrasive wear.The wear of the tool noses was much smaller,but a large scale of thermally activated flaking and brittle fracture occurred at the cutting area.The final failures of pure WC cutting tools were defined as a typical mechanical fatigue crack extension.The main tool wear type of SiC-TiC cutting tools in dry cutting HT200 grey cast iron was abrasive wear,a groove-shaped breach on the cutting edge has been observed.The tool life of pure WC cutting tools is longer than that of YW2 and SiC-TiC cutting tools in cutting HT200 grey cast iron with the same cutting parameters due to the low adhesion of grey cast iron to the pure WC material.