Study On TiAlN-based Composite Nano-coating Tool For High-speed Cutting Titanium Alloys Prepared By Magnetron Sputtering

Titanium alloy is widely used in military and civil fields because of its excellent comprehensive performance.It is one of the preferred materials for lightweight and special environments.However,titanium alloys have the characteristics of high temperature strength,low modulus of elasticity,high reactivity and high friction coefficient.Titanium is one of typical hard-to-cut materials with high cutting costs,which limits the application of titanium alloys.Coated tool is materials-deposited on the tool substrate,it can maintain the toughness of the base material and significantly improve tool wear resistance,hardness and other properties,is the most widely used cutting tool at present.However,there are some problems such as tool tremor,severe bond wear and large friction coefficient when the coated tool is cutting titanium alloy.The current tool coating is difficult to meet the requirements of titanium alloy machining.Therefore,it is necessary to develop the titanium alloy cutting feature,excellent mechanical properties,low affinity and low friction coefficient tool coating.Based on the above background,in order to solve the problem of high affinity and large friction coefficient during the cutting of titanium alloy,the low-affinity TaO coating and the self-lubricating WS coating was prepare by magnetron sputtering,then we prepared low affinity and self-lubricating functional composite coating.For low-affinity TaO coating,we investigated the effects of different thickness on the microstructure and low-affinity of the coating.For the self-lubricating WS coating,the effects of the growth mode of WS on the self-lubricating properties such as friction coefficient was investigated.For the functional composite coatings,the effects of the composite methods on the affinity and self-lubricating properties were mainly investigated.Finally,the preparation methods of the coatings were proposed to eliminate the bond wear and reduce the friction coefficient at the same time.The main results are as follows:(1)Low affinity TaO coating research,different thickness TaO was deposited on the TiAlTaN coating surface,mainly study the impact of TaO on the bonding wear when machine titanium alloy.It was found that as the coating thickness increased,the coating surface became denser,the roughness and friction coefficient decreased.In tribological experiments,as the thickness of TaO increases,the volume of titanium alloy on the coating surface decreases.The TaO coating was deposited on different coatings and substrates,then we studied their cutting performance.While the TiAlTaN coating and TiAlTaN/TaO coating were deposited on the domestic coarse-grained WC tool substrate,the cutting distance of TiAlTaN coating is only 115 m,the cutting distance of TiAlTaN/TaO coating can up to 356 m.At the same time,the TaO coating was prepared on imported commercial coating tools,after its cutting distance of 547 m,the tool flank wear was only 0.214 mm.When TaO was absent,the coating had worn when the cutting distance of 115 m.(2)Self-lubricating WS coating research,the WS self-lubricating coating was prepared by magnetron sputtering,its friction coefficient as low as 0.198.It was embedded in TiAlN coating to form a composite self-lubricating coating,in the friction process,WS continuous precipitation can achieve the role of self-lubricating.The coating is mainly composed of bond wear,abrasive wear and brittle fracture.The WS was embeded into TiAlTaN coating,it can reduced the friction coefficient of the coating from 1.02 to 0.37 compared with pure TiAlTaN coating,while the hardness of the coating still can remian above 25 Gpa.(3)Functional composite coatings,the effects of WS columns with diameters of 75 ?m and 100 ?m on the properties of the composite coating were studied.The size of the WS column was found to affect the surface morphology of the coating.When the size was 100 ?m,the surface of the coating became larger and the hardness of the coating was between the hardness of TaO and TiAlTaN,which was about 16 GPa.The tribological properties of the coatings were tested and it was found that the friction coefficient of the coating was significantly decreased,the value was just 0.28 and 0.21 respectively,which decreased by 72.5%and 79.4%respectively compared to TiAlTaN.