Ying Fei Ge

Experimental Study on High Speed Milling of γ-TiAl Alloy

This paper deals with the milling machinability of gamma titanium aluminide at speeds of 60-240m/min. The results showed that surface roughness was less than Ra0.44μm at all cutting speeds used in the tests even when the tool wear reached VB0.2mm. The milling forces increased slightly with increasing cutting speed but increased rapidly with the elevated flank wear value especially for the Fy component. Compared to those of titanium alloy TA15, the milling forces of γ-TiAl were 190%, 180% and 200% greater for Fx, Fy and Fz respectively under the same machining conditions. Workpiece surface has a maximum microhardness of approximately 600HV0.100, and the depth of maximum hardened layer was confined to 180μm below the surface. When cut with TiAlN coated carbide tool, tool life was 35 min which was only about 1/2 of that for titanium alloy TA15.

High-Speed Turning of Titanium Matrix Composites with PCD and Carbide Tools

High-speed turning tests were performed on vol.10%(TiCp+TiBw)/TC4 composite (TMC) in the speed range of 60-120m/min using PCD and carbide tools to investigate the tool life, tool wear, cutting temperatures and cutting forces. The results showed that the carbide tool was not suit for the machining of TMC. Tool life of PCD was confined to 12 min for all the cutting conditions. Flank wear increased obviously with the increasing cutting speed especially when the cutting speed surpassed 80m/min. PCD tool mainly took place chipping, peeling, abrasive wear and adhesive wear at the rake face and flank. The cutting temperatures of carbide were about 1.5-2.0 times higher than that of the PCD. Under the same cutting condition, cutting temperature of TMC was nearly 100°C higher than that of the TC4 matrix. The cutting forces were confined to 130N and 150N for the PCD and carbide tool respectively. For the carbide the cutting forces slightly decreased when the cutting speed increased from 60m/min to 120m/min. When using the worn tool, the cutting forces significantly decreased with the increasing cutting speed especially for the peripheral force component.

Experimental Study on the Milling of a High Strength Titanium Alloy

A series of experiments were carried out on normal and high speed milling of a high strength titanium alloy (TA15). TA15 is a close alpha titanium alloy strengthened by solid solution with Al and other component. It is often used to make large structural parts in airplane and welded parts subject to heavy load. The tool life of several typical types of cutter commonly used in the milling of titanium alloy was studied by the orthogonal experiment design method. After multi-element regression analysis, the empirical equation of the tool life was stablished. The milling force and temperature were measured under different cutting conditions and tool wear status. The knowledge is useful to further understand and analysis of the cutting mechanism, machining quality and tool wear. The study on the machined surface integrity includes the following content: surface roughness, metallographic examination, work hardening and residual stress.

Cutting Temperature and Cutting Forces Investigation Based on the Taguchi Design Method when High-Speed Milling of Titanium Matrix Composites with PCD Tool

High-speed milling tests were performed on vol. (5%-8%) TiCp/TC4 composite in the speed range of 50-250 m/min using PCD tools to nvestigate the cutting temperature and the cutting forces. The results showed that radial depth of cut and cutting speed were the two significant influences that affected the cutting forces based on the Taguchi prediction. Increasing radial depth of cut and feed rate will increase the cutting force while increasing cutting speed will decrease the cutting force. Cutting force increased less than 5% when the reinforcement volume fraction in the composites increased from 0% to 8%. Radial depth of cut was the only significant influence factor on the cutting temperature. Cutting temperature increased with the increasing radial depth of cut, feed rate or cutting speed. The cutting temperature for the titanium composites was 40-90 °C higher than that for the TC4 matrix. However, the cutting temperature decreased by 4% when the reinforcements volume fraction increased from 5% to 8%.

Experimental Study on Milling of Titanium Matrix Composites

Titanium matrix composites (TMCs) possess many outstanding properties and have increasing and potential application in aerospace, automobile and other industries. However, TMCs are typical difficult-to-machining material due to the rapid tool wear rate and excessive machining induced defects. In this paper, tool wear, cutting forces, cutting temperature and surface roughness were investigated when milling TMCs with Polycrystalline Diamond (PCD) and carbide tools. The results showed that the values of surface roughness obtained by carbide tools were higher than that of PCD tools under the same cutting conditions. The value of cutting temperature for PCD tool was about 75% of the carbide tools, and the main cutting force value of PCD tool was about 85% of the carbide tool. Abrasive and adhesive wear were the main wear mechanisms of PCD and carbide tools. In all, PCD tools had a better cutting performance than carbide tools during finishing milling titanium matrix composites.

High Speed Machining of Particulate Reinforced Metal Matrix Composites with PCD Tools

Polycrystalline diamond (PCD) tools were used in high speed machining of SiCp/2009Al and TiCp/TC4 composites. The results showed that milling forces decreased with the increasing cutting speed, and that the force value of vol.20%SiCp/2009Al was less than that of the matrix. The machined surface roughness Ra is less than 0.8μm for all the milling experiments until cutting time was 180 minutes. The machined surface included some defects such as scratches, craters, micro cracks and so on. Surface finish can be improved through increasing cutting speed. When milling, gradual flank wear and slight edge chipping took place on the PCD tool flank. But no obvious abrasive wear was observed. However, the PCD tool suffered from significant abrasive wear in the flank when turning. A flow type chip was formed either for milling or turning when vol.20%SiCp/2009Al was used. Some voids and micro cracks were found in the chip. For TiCp/TC4 composite, the chip took the form of interrupted saw-toothed due to the dynamic behavior of micro crack. Although PCD tool was very suitable for high speed machining of SiCp/2009Al, its geometry parameters must be rightly chosen for TiCp/TC composite, or else sever edge chipping would take place in a few minutes.

Diamond Tool Wear Mechanism in Ultra-Precision Turning of SiCp/Al Composites

The wear pattern and its mechanisms of Single Crystal Diamond (SCD) tool has been investigated experimentally and theoretically during ultra-precision turning of SiC particle-reinforced aluminum matrix composite. The results showed that micro wear, chipping, peeling, abrasive wear and chemical wear were the dominating wear patterns of SCD tools. Coupled with XRD analysis on the machined surface and Raman studies on the flank wear land of SCD tool, it was pointed that the combined effects of abrasive wear of SiC particles and catalysis of copper in the aluminum matrix have caused the severe graphitization.

Surface Generation and Chip Formation when Ultra-Precision Turning of SiCp/Al Composites

Chip formation and surface generation were investigated when ultra-precision turning of SiCp/2009Al and SiCp/ZL101A composites using Single Crystal Diamond (SCD) and Polycrystalline Diamond (PCD) tools. The results showed that the machined surfaces took on many defects of pits, voids, microcracks, grooves, protuberance, matrix tearing etc. It was noticed that most of these defects had an intimate relationship with the removal process of SiC particle. The surface finish was much better when the SiC particles were removed by cut through or in-situ pressed into mechanisms. Material swelling and side flow, tool-workpiece relative vibration, feed rate and tool nose radius, removal mode of SiC particles were these main mechanisms of surface generation. Generally, a saw-toothed chip was formed when ultra-precision turning this kind of material and the mechanisms of this type of chip were dynamic microcrack behavior and strain concentration, which induced by the non-uniform deformation of the workpiece material.

Advances in High-Speed Milling of Metal Matrix Composites

Particle reinforced metal matrix composites (PMMC) possess many outstanding properties and are increasingly applied in automobile, aerospace, electronics and medical industries. However, PMMC is a typical difficult-to-machining material due to the rapid tool wear rate and excessive machining induced defects. Although large amount of investigations have been done on the conventional machining of PMMC, merely several researchers have dedicated themselves to the study of milling, especially high speed milling of this material. Within the milling studies, most researchers have selected the carbide coated or uncoated solid carbide tools whose tool life was not satisfactory for engineering application. The literatures review indicates that most researchers limited their study to sintering or casting SiCp/Al composites at the low or moderate cutting speed. Material produced by the in-situ reaction method or titanium matrix composites was seldom selected as the research object. The research content was limited to the effect of cutting parameters on the machined surface quality or cutting forces. It is suggested that high-speed milling with PCD tool should be conducted in order to improve the machined surface quality and material removal rate and decrease the machining cost. Tool life modeling, surface roughness prediction, cutting parameters optimization and high-speed milling data base and the expert system should be greatly noticed by the researchers.

Cutting Temperature Investigation when High-Speed Milling of SiCP/Al Composites

High-speed milling tests were performed on SiCp/2009Al composites in the speed range of 600-1200m/min using PCD tools to investigate the cutting temperatures and the influence factors. The results showed that the cutting temperature could reach 580°C under the given cutting conditions. Graphitization took place on the PCD tools under the high cutting temperature coupled with the effects of abrasive wear of SiC particles and catalysis of copper in the 2009 aluminum matrix. Cutting parameters, tool materials, workpiece materials and tool wear condition had significant effect on the high speed milling temperature while tool geometries had the minor effect. Among these influence factors, cutting speed was the most significant factor. Reinforcement volume fraction was the less significant factor and followed by radial depth of cut, feed rate and tool materials.