Study On The Precision Manufacturing Of Cermet Micro End-mill Tool And Its Cutting Performance

With the development of the micro/nano science and technology, micro machine have been the new equipment in micro area, which have a wide application prospect in aerospace, precision apparatus and bio-medical. Micro machining include LIGA, focused ion beam, micro electro-discharge, micro cutting and so on at current study, which accelerate the development of micro machine. Micro milling is one of micro machining technologies. It is capable to machine various engineering materials with a relatively high material removal rate, and allows for the complex three dimensional structures in the field of micro machining. Generally, micro milling tool is made of ultra-hard material including tungsten carbide and poly-crystalline diamond (PCD). Cermet has not been used to machine micro end-mill tool at present study. However, tungsten carbide tool is usually used to machine the alloys having poor mechanical properties. PCD are widely used to machine nonferrous metals in micro machining due to its high hardness and low friction coefficient. Thus, this study attempts to manufacture the micro end-milling tool using Ti(C7N3)-based ceramic material and micro end-mill tool with the diameter of (?)0.5～(?)1.0 mm were successfully fabricated. There were used to machine LY12 to verify the feasibility of cermet micro end-mill tool. The main contents are summarized as follows in this study:Cermet tools were manufactured from micro and macro area, especially feasibility of the cermet micro milling tool were study. In macro area, cermet tools were used to turning hastelloyC-276, H13,1Cr18Ni9Ti,17-4PH. Results indicated that the best cutting performance of three Ti(C7N3)-based cermet tool is Ti(C7N3)/TaC/WC, thus, Ti(C7N3)/TaC/WC micro end-mill tool were manufactured. The fatigue life and micro hardness of Ti(C7N3)/TaC/WC were investigated. Results indicated that the crack propagation coefficient of Ti(C7N3)/TaC/WC are 36,131805(N, R) respectively. The micro hardness decreases with the increasing of loading force, when the load force is 1N, the micro hardness of cermet is 29 GPa by nano indentation method.The ratio of each part of micro end-mill tool was optimized by establishing the mathematical model to investigate the deformation of micro end-mill tool. Based on finite element analysis method, the stress and strain of various kind of cermet tool tips structure were investigated. Triangular, quadrangular, pentagonal and hexagonal of cermet micro end-mill tool with diameter of φ1.0 mm and φ0.5 mm were successfully manufactured by using wire electrical discharge machining. The screw structure of cermet micro end-mill tool with diameter of φ1.0 mm,φ0.8 mm and φ0.5 mm were fabricated by using precision grinding. The least square method was used to fit out the cutting edge radius. It showed that the cutting edge radius of cermet micro end-mill tool with diameter of φ1.0 mm,φ0.8 mm and φ0.5 mm was 4.125 μm、4.319μm and 3.89μm respectively.The cutting performance of cermet micro end-mill tool was investigated in cutting LY12. Results indicated that workpiece machined surface own poor quality due to micro tool tip serious ploughed with workpiece when the rule structure of cermet micro tool with the diameter of φ1.0 mm were used. However, when the rule structure of cermet micro tool with the diameter of φ0.5 mm were used to machine LY12 at n=20000 r/min,ap=2μm, f=4μm/z, machined surface roughness was 0.92 μm. The optimal cutting parameters of screw structure of cermet micro end-mill tool with diameter of φ1.0 mm was n=30000 r/min, ap=100μm, f=2μm/z by single factor experiment method. In that case, the tool diameter decreased to about 3.13% after machining time 50 min, and the machined surface roughness was 0.44μm. At the same cutting parameters, the tip fracture of WC micro end-mill tool (176μm) was greater than Ti(C7N3)-based cermet micro end-mill tool. Additionally, failure modes and failure mechanism of Ti(C7N3)-based cermet micro end-mill tools were thoroughly discussed. The results indicated that the main failure mode was tool tip micro chipping and failure mechanism was adhesive wear using cermet micro end-mill tool with the diameter of φ1.0 mm and φ0.8 mm. The main wear mechanisms of the cermet micro end-mill tool with the diameter of φ0.5 mm were micro-crack initiation and crack propagation resulting in tool tip fracture failure due to stress concentration at cutting edge root.