Research On The Matching Of Cutting Tools And Workpieces Of Titanium Alloys Machining

Titanium alloys is widely applied to astronautics, automobile, the chemical industry etc because of its fine characteristic. But the titanium alloys is a typical material that is difficult to be machined, and there is few research on matching of the cutting tool material and the workpieces materials, the research of chemical, physical and mechanical matching between the tools and the workpieces on titanium alloys (Ti-6Al-4V) machining was carried, and the results was confirmed through end milling experiment of Ti-6Al-4V titanium alloy, the cutting tool selective system model of the titanium alloy was established.The research of chemistry matching is carried on from the oxidation and diffusion of cutting tools to titanium alloys. chemical thermodynamics computation and oxidation test on cutting tools and titanium alloys were studied, the results indicated that YT cemented carbide tools oxidation weightlessness is less, the anti-oxidation ability is stronger, WC and Co in YG cemented carbide specimen had already been oxidized in 800 ℃, but the TiC in YT cemented carbide tools has not been oxidized. The YW cemented carbide tools containing TaC (NbC) has the better anti-oxidized ability; the anti- oxidized ability of fine grain cemented carbide tools is better than that with coarse grains. When 800 ℃, TiO₂ and Ti₄N₃ were examined in the Ti-6Al-4V specimen surface, the further oxidation was prevented by the protection of superficial oxidation film in 1000 ℃.The diffusion test results indicated that there is diffusion between cemented carbide tools and Ti-6Al-4V, but the diffusion degree is slight in 400 ℃. Diffusing phenomena are quite obvious in 600 ℃, the diffusion degree of W and Co elements in YT15 is more obvious than that in YG3 and YG3X; crystal grain of cutting tools material is thicker, the diffusion is easier. The oxidation phenomenon prevented diffusion between cutting tools and titanium alloys in 800 ℃. From the matching research of mechanical properties , the YG8 cemented carbide tools with higher bending strength and impact toughness is more suitable for rough machining and free of oxide coat when machining the titanium alloys; YG3 and YG3X cemented carbide tools with higher hardness is more suitable for finish machining of the titanium alloys; YG6 and YG6X cemented carbide tools are widely used in the semi-finishing and finishing machining; TaC(NbC) can enhance the high temperature hardness, intensity and toughness of cutting tools material in high temperature, so YG6A and YW2 cemented carbide tools containing TaC and NbC can be used in high speeding machining.From the matching of physical performance, YG3, YG3X with bigger thermal conductivity, elasticity coefficient and smaller thermal-expansion coefficient are suitable for the finishing machining, and YG8, YG8X with smaller thermal conductivity, elasticity coefficient and bigger thermal-expansion coefficient are suitable for the rough machining.The cutting performance of YG8 and YT15 cemented carbide tools were studied through milling tests; the results indicate that the wear of YG8 cemented carbide tools is smaller than that of YT15 cemented carbide tools when cutting Ti-6Al-4V materials, and there is no tipping and breakage on YG8 cemented carbide tools. So YG8 cemented carbide tools is more suitable for milling Ti-6Al-4V materials in low speed than YT15 cemented carbide tools. Abrasive wear was found to be the main mode of flank wear, while abrasive wear and adhesive wear were the main rake face wear types. It is common that several tool wear patterns may appear simultaneously at the same time and have an effect on each other.The development of cutting-tools' selecting system for machining titanium alloys has completed through system design and database design, using Visual C# software and Microsoft SQL Server2,000 database management system. This program can help producers and designers to recommend suitable cutting tools and appropriate cutting parameters according to the request of processes, therefore, it can reduce the intensity of work and increase theproductivity.