Influence of cutting speed and tool wear on the surface integrity of the titanium alloy Ti-1023 during milling

The International Journal of Advanced Manufacturing Technology, Dec 2014

This study focuses on the machined surface integrity of the titanium alloy Ti-10V-2Fe-3Al (Ti-1023) during face milling. Surface roughness, machining defect, microhardness, and microstructure variations are investigated at different cutting speeds and tool average flank wear (VB) values. Experimental results show that surface roughness increases when cutting speed is increased from 40 to 100 m min−1 and decreases when cutting speed is increased from 100 to 300 m min−1 by using a new tool. Moreover, surface roughness values are stable when cutting speed is increased by using a worn tool at VB = 0.2 mm and increases when VB is increased. As for defects, the machining defect is determined to be dependent on cutting speed and tool wear directions. Microhardness is decreased to 35 μm beneath the machined surface at different cutting speeds by using a new tool. The influence of tool wear on hardening is significant, with the depth of hardening being less than 55 μm by using a worn tool at VB = 0.2 mm and reaching 130 μm at VB = 0.35 mm. No significant phase transformation or evident deformation can be observed at different cutting speeds by using a new tool (initial wear). Severe plastic deformation and deep alteration of the microstructure in the machined surface are produced with VB from initial wear to VB = 0.35 mm. VB is best maintained at less than 0.2 mm for finish machining of Ti-1023.

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Influence of cutting speed and tool wear on the surface integrity of the titanium alloy Ti-1023 during milling

Yang Houchuan Chen Zhitong Zhou ZiTong 0 ) Department of Aviation Repair Engineering, The First Aeronautical Institute of Air Force , Xinyang, Henan Province 464000 , China This study focuses on the machined surface integrity of the titanium alloy Ti-10V-2Fe-3Al (Ti-1023) during face milling. Surface roughness, machining defect, microhardness, and microstructure variations are investigated at different cutting speeds and tool average flank wear (VB) values. Experimental results show that surface roughness increases when cutting speed is increased from 40 to 100 m min1 and decreases when cutting speed is increased from 100 to 300 m min1 by using a new tool. Moreover, surface roughness values are stable when cutting speed is increased by using a worn tool at VB = 0.2 mm and increases when VB is increased. As for defects, the machining defect is determined to be dependent on cutting speed and tool wear directions. Microhardness is decreased to 35 m beneath the machined surface at different cutting speeds by using a new tool. The influence of tool wear on hardening is significant, with the depth of hardening being less than 55 m by using a worn tool at VB=0.2 mm and reaching 130 m at VB=0.35 mm. No significant phase transformation or evident deformation can be observed at different cutting speeds by using a new tool (initial wear). Severe plastic deformation and deep alteration of the microstructure in the machined surface are produced with VB from initial wear to VB = 0.35 mm. VB is best maintained at less than 0.2 mm for finish machining of Ti1023. 1 Introduction The titanium alloy Ti-10V-2Fe-3Al (Ti-1023) has been extensively used to manufacture critical components, such as aircraft fuselage, wing, landing gear, and helicopter rotor parts, employed in the aviation and aerospace industries because of its high strength-to-weight ratio, excellent corrosion and fatigue resistance, high fracture toughness, good casting properties, and hardenability [1]. These critical components are frequently used in extreme environments. The processing quality of these components directly affects the performance of the entire aircraft structure [2]. Finishing is still needed to satisfy tolerance requirements or achieve improved surface integrity. However, similar to other titanium alloys, Ti-1023 cannot be easily machined because of its high strength, chemical reactivity, and low thermal conductivity. Numerous investigations have confirmed that the performance, longevity, and reliability of machined components during their service life are considerably dependent on their surface quality [3]. Surface integrity requirements (e.g., surface roughness, machining defect, microhardness, microstructure, and residual stress) must be satisfied to eliminate severe failures produced by fatigue, creep, and stress corrosion cracking generated on the surface of components [46]. Hence, the quality of a machined surface is important to satisfy the increasing demands for sophisticated component performance. Many studies have been conducted to investigate the surface integrity of titanium alloys, including Ti-6Al-4V, Ti6242S, and Ti-6246 [713]. Sun and Guo [8] reported that roughness is obviously influenced by cutting speed and tool wear. As cutting speed increases, roughness value decreases. Consequently, the machined surface tends to become smooth toward the end of tool life at a cutting speed of 60 m min1. Other researchers have reported that cutting speed [7, 911, 15] is effective to a certain degree in increasing surface roughness. As cutting speed is increased, surface roughness increases for Ti-6246 and Ti-64 [7, 8, 13, 14]. Moreover, tool parameters, such as tool insert shape, tool average flank wear (VB), and the selected coolant, affect surface roughness values [16]. Tool wear close to tool half-life results in a slight decrease in surface roughness values than that in the previous period. When half-life is reached, the tool fits the workpiece and surface roughness is decreased. After half-life, however, the tool starts to wear severely and causes anomalies in the toolworkpiece contact surface, which increases surface roughness significantly [13]. Many forms of surface defects have been reported in literature [12, 15, 1720]. The main forms include surface drag, material pullout/cracking, feed marks, adhered material particles, tearing surface, chip layer formation, microchip debris, surface plucking, deformed grains, surface cavities, slip zones, laps (materials folded onto the surface), and lay patterns [12, 15, 1720]. Cutting speed can affect the amount of microchip debris on the surface [12, 17]. The most commonly reported surface damages are plastic deformation of the grains in the direction of cutting and surface cavities. Jeelani and Ramakrishnan [21, 22] reported that surface cavities are formed by chip fragmentation on the workpiece surface or by welding between the titanium adhering to the tool and the workpiece. The adher (...truncated)


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Yang Houchuan, Chen Zhitong, Zhou ZiTong. Influence of cutting speed and tool wear on the surface integrity of the titanium alloy Ti-1023 during milling, The International Journal of Advanced Manufacturing Technology, 2015, pp. 1113-1126, Volume 78, Issue 5-8, DOI: 10.1007/s00170-014-6593-x