A Study of Surface Integrity when Machining Refractory Titanium Alloys

Ginting, Armansyah; Nouari, Mohammed; Lebaal, Nadhir

doi:10.4028/www.scientific.net/AMR.83-86.1059

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HomeAdvanced Materials ResearchAdvances in Materials and Processing TechnologiesA Study of Surface Integrity when Machining...

A Study of Surface Integrity when Machining Refractory Titanium Alloys

Abstract:

In this paper, the surface integrity is studied when machining the aeronautical titanium alloys. Surface roughness, lay, defects, microhardness and microstructure alterations are studied. The result of surface roughness judges that the CVD-coated carbide fails to produce better Ra value than the uncoated. Lay is characterized by cutting speed and feed speed directions. Feed mark, tearing surface, chip layer formation as built up layer (BUL), and deposited microchip are the defects. Microhardness is altered down to 350 microns beneath the machined surface. The first 50 microns is the soft sub-surface caused by thermal softening in ageing process. Microstructure alteration is observed in this sub-surface. Down to 200 microns is the hard sub-surface caused by the cyclic internal work hardening and then it is gradually decreasing to the bulk material hardness. It is concluded that dry machining titanium alloy is possible using uncoated carbide with cutting condition limited to finish or semi-finish for minimizing surface integrity alteration.

Info:

Periodical:

Advanced Materials Research (Volumes 83-86)

Main Theme:

Advances in Materials and Processing Technologies

Edited by:

M. S. J. Hashmi, B. S. Yilbas and S. Naher

Pages:

1059-1068

DOI:

https://doi.org/10.4028/www.scientific.net/AMR.83-86.1059

Citation:

A. Ginting et al., "A Study of Surface Integrity when Machining Refractory Titanium Alloys", Advanced Materials Research, Vols. 83-86, pp. 1059-1068, 2010

Online since:

December 2009

Authors:

Armansyah Ginting, Mohammed Nouari, Nadhir Lebaal

Keywords:

Carbide, CVD-Coated, Cyclic Internal Work Hardening, Microhardness, Roughness, Thermal Softening

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References

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Paper TitlePages

Tool Wear and Surface Integrity in High Speed Milling of Forging and Cast TA15 Alloys with Coated Carbide Tools

Authors: P. Liu, Jiu Hua Xu, Yu Can Fu

Abstract: TA15 (Ti-6.5Al-2Zr-1Mo-1V) is a close alpha titanium alloy strengthened by solid solution with Al and other component. A series of experiments were carried out on normal and high speed milling of TA15. The recommended tools for many years had been the uncoated tungsten carbide grade K. In this work, the tool life of coated carbide tools used in high speed milling of forging and cast titanium alloy was studied. Additionally, the wear mechanism of cutting tools was also discussed. Finally, surface integrity, including surface roughness, metallograph and work hardening, were examined and analyzed. The result shows that the surface quality of forging and cast machined by carbide cutter is similar, but the tool life of carbide in high speed milling of forging TA15 is longer than that in high speed milling of cast TA15.

189

Investigation on White Layer Formation in PCBN Hard Turning GCr15

Authors: Bao Yun Qi, Ning He, Liang Li, Wei Zhao

Abstract: It is commonly believed that the white layer formed during hard machining of steels is caused primarily by a thermally induced phase transformation resulting from rapid heating and quenching. The focus of this study is to investigate the white layers produced on the machined surfaces and on the inner side part of the chips in dry hard turning GCr15 with PCBN tools. Samples of machined workpiece and chips were metallographically processed and observed under a microscope to determine whether white layers were present or not. Some properties of white layers were deduced in order to verify some of the prevalent theories. More specifically, chip shapes were studied to determine how they developed during machining with potential appearance of white layers, with a view to correlating the chip shapes with the white layer formation.

241

Identification of Subsurface Deformation in Machining of Inconel 718

Authors: Jin Ming Zhou, Volodymr Bushlya, Ru Lin Peng, Jan Eric Stahl

Abstract: There is considerable industrial significance to understand the nature of subsurface deformation under the machined surface for correct prediction of surface properties in machined components based upon the machined conditions and material behaviors that give rise to them. In this study, high speed machining of Inconel 718 was carried with whisker reinforced ceramic cutting tool under different conditions of tool wear, coolant state and cutting parameters. The objective of the present investigation was to determine the effect of both cutting parameters and tool wear on the plastic deformation in the subsurface region of Inconel 718 after the finishing machining with above process conditions. The surface and subsurface region of machined specimens were examined using a high resolution scan electron microscope (HRSEM) and EBSD technique, microhardness measurements were also conducted on the test samples, accordingly plastic strain analysis were carried out.

1681

Influence of Cutting Parameters on Surface Characteristics for Milling Powder Metallurgy Nickel-Based Superalloy

Authors: Yang Qiao, Xing Ai, Zhan Qiang Liu

Abstract: Powder metallurgy (PM) nickel-based superalloy is regarded as one of the most important aerospace industry materials, which has been widely used for engine components. As the demands of the service performance increase, the surface characteristics are becoming more and more important. However, the machined surface of PM nickel-based superalloy is easily damaged due to its poor machinability. A series of milling experiments in a wide range of speeds were carried out to investigate the effects of dry milling parameters on the surface characteristics of PM nickel-based superalloy. The machined surface is evaluated in terms of surface roughness and work hardening. The results show that, milled surface characteristics of PM nickel-based superalloy are sensitivity to the cutting speeds. The machined surface roughness increases with increase of the cutting speed, but with further increase of cutting speed between 70 to 90 m/min and 150 to 170 m/min two decreases in surface roughness appear. For work hardening, it can be seen that the machined workpiece surface hardens seriously.

1635

Surface Integrity in Micromilling of Hardened AISI D2 Tool Steel

Authors: J.B. Saedon, S.L. Soo, D.K. Aspinwall, A. Barnacle, N.H. Mohamad Nor

Abstract: This paper presents workpiece surface integrity of micromilling hardened tool steel AISI D2. These include 3D mapping of surface texture, analysis of microstructure and microhardness variation. The results indicate no evidence of major surface damage such as microcracks, un-tempered/over-tempered martensite, phase transformations or white layer formation was detected in any of the specimens analysed. No discernible deformation of the material grain structure beneath the machined surface was observed. This was mainly attributed to the comparatively low levels of mechanical force and temperatures generated during the micro milling operation.

151