Wear Characteristic And Performance Of Cutting Tool In High-efficiency Machining Ti6Al4V

The development of modern manufacturing technology aims to achieve high efficiency, high precision, high flexibility, and greenization machining, especially, high efficiency is the main objective. Titanium alloys have been used widely in aerospace industry in recent years owing to their superior properties, such as excellent strength-to-weight ratio, high corrosion resistance and ability to retain high strength at high temperature. However, they are classified as difficult-to-cut materials because of their low thermal conductivity, high chemical reaction and low modulus of elasticity. The serious tool wear limits the development of the technology of high-efficiency machining difficult-to-cut material. Therefore, the present study aims at analyzing wear characteristic and performance of carbide tool in high-efficiency machining titanium alloy Ti6Al4V, and then providing theoretical basis for tool wear controlling, optimization of tool material and cutting parameters. This can promote the development and application of high-efficiency machining technology.First, an experimental investigation employing coated carbide tool is presented in the first part of the thesis to study the characteristics of cutting force and cutting temperature in machining Ti6Al4V. The effects of tool flank wear on cutting force were studied. The cutting force model incorporating tool flank wear effects were established in the light of classical orthogonal cutting model.Second, according to the tribological characteristics of tool-chip interface and tool-workpiece interface, tool wear mechanism and the effects of cutting condition on tool wear behavior were studied in this part. In machining Ti6Al4V, there exist serious adhesion, diffusion and oxidation at tool rake face and flank face. Adhesion wear in flank race is severer than rake face because of high pressure in tool-workpiece interface. However, diffusion wear in tool rake face is severer than tool flank face. According to tool wear mechanism, the physical evolution process that tool materials in tool rake face lost and peel off from tool substrate was studied.Third, as different tool material and different cutting edge radius show different performance in machining titanium Ti6Al4V, the tool wear characteristic, tool life, static and dynamic characteristic of cutting force and cutting temperature with different tool material were analyzed respectively. AHP method was used to evaluate the performance of cutting tool and the results showed that uncoated carbide tool with fine grain shows best performance than coated tools containing Ti element. Finite element analysis was used to analyze the mechanical-thermal characteristic in machining titanium Ti6Al4V. The performance of round cutting edge was evaluated by wear and the mechanical-thermal characteristic. There exists an optimal cutting edge radius that makes round cutting edge show optimal performance within a certain range.Finally, the tool flank wear model was established involving uncoated carbide tool. The wear model can predict tool flank wear within a certain range. Cutting parameters were optimized in the light of established wear model. The wear map method was used to study tool wear. Tool wear map for uncoated carbide tool in machining Ti6Al4V was constructed. It can provide a global understanding of the effects of machining conditions on tool wear. It made possible using the constructed wear map for cutting parameters choice to attain a desirable productivity at an acceptable tool wear rate. This can provide theoretical basis for optimization of cutting parameters, tool wear controlling, increasing tool life and achieving high-efficiency machining titanium.?...