Experiment Research On High Speed Machining Of Titanium Alloy With PCBN

Titanium alloys have been widely used in the national defense and civil industry, especially in the aerospace, because of their prominent performance excellence. Many structures of the airplane are presently made of thin-walled parts, which need high material removal rates in the cutting process. While titanium alloys are difficult-to-cut materials, with low cutting rates and high tool wear rates. In machining thin-walled parts, they are very easy to deform, too. So the issue of machining titanium alloy is always a problem which need be resolved immediately. With the application of high speed machining technology, high speed machining titanium alloy has became a focus field in the research of whole world.There are many investigations of cutting titanium alloy and a great deal of achievements have been made, such as cutting performance and surface integrality, tool wear and tool life and so on. However, a great number of researches have been done in the low cutting speed due to the poor machinability of titanium alloys. In this thesis, the theoretical and experimental researches on cutting force, surface quality, tool failure shape and failure mechanism, and tool life of high speed machining titanium alloy Ti6A14V will be carried out in order to provide methods with the development of new tool materials and the increase of tool life.Cutting force is one of the important physics parameters in machining processes, influencing machining precision and machining quality. Surface roughness is a criterion of surface quality and reflects the condition of tool wear and failure. Based on the characteristic of PCBN tool material and titanium alloy Ti6A14V workpiece, single-factor experimentation will be made to research on cutting force and machined surface roughness. It is proved that stabile cutting force and lower surface roughness are gained in machining titanium alloy Ti6A14V used PCBN compared with other tool materials. Tool failure influences tool life and machined surface quality directly, and influences machining cost and machining efficiency. Tool failure shape and failure mechanism in high speed machining titanium alloy Ti6A14V used PCBN tool will be researched by micrographic experiments (SEM and EDS) and analysis. It is found that the tool failure shapes of PCBN tool are wear and fracture, and the primary tool failure mechanisms are mechanical wear, chemical wear and brittle fracture. It is proved that dominant failure mechanisms are different with different cutting conditions. When the cutting factors are all in the low level or in the early and middle cutting process, mechanical wear is the dominant failure mechanism. While with the increase of cutting factors or in the late cutting process, chemical wear and brittle fracture are more and more salient due to the increase of the cutting heat.Tool life is the key problem of the high speed machining technology. It is a focus of the investigators. This thesis uses the opposite angle-orthogonal regression experiment to work out the empirical equation of tool life. The influence of cutting factors is analyzed, viz. the influence of cutting depth is primary, the influence of cutting speed is second, and the influence of feed rate is last. Tool wear law is depicted via analyzing tool life. When the feed rate and cutting depth are in the low level, the increase of wear rate is rapidly at early cutting process, steady at the middle cutting process and very sharply at the lately of cutting process. When the feed rate and cutting depth are in the high level, tool failure is very bad, and tool life is very short.