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- 2019
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Tidskriftsartikel (refereegranskat)
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| 2. |
- Chen, Zhe, 1987-, et al.
(författare)
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Effect of Machining Parameters on Cutting Force and Surface Integrity when High-Speed Turning AD730™ with PCBN Tools
- 2019
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Ingår i: The International Journal of Advanced Manufacturing Technology. - : Springer London. - 0268-3768 .- 1433-3015. ; 100:9-12, s. 2601-2615
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Tidskriftsartikel (refereegranskat)abstract
- The novel wrought nickel-based superalloy, AD 730™, is a good candidate material for turbine disc applications at high temperatures beyond 650 °C. The present study focuses on the machining performance of this newly developed alloy under high-speed turning conditions with advanced PCBN tools. Meanwhile, the machined surface integrity as influenced by cutting speed and feed rate was also investigated. The surface integrity was thoroughly characterized in terms of surface roughness and morphology, machining-induced plastic deformation, white layer formation, and residual stresses. It has been found that the cutting speed and feed rate had a strong effect on the cutting forces and resultant surface integrity. The cutting forces required when machining the alloy were gradually reduced with increasing cutting speed, while at 250 m/min and above, the flank tool wear became stronger which led to increased thrust force and feed force. A higher feed rate, on the other hand, always resulted in higher cutting forces. Increasing the cutting speed and feed rate in general deteriorated the surface integrity. High cutting speeds within the range of 200–250 m/min and a low feed rate of 0.1 mm/rev are preferable in order to implement more cost-effective machining without largely reducing the surface quality achieved. The formation of tensile residual stresses on the machined AD 730™, however, could be of a concern where good fatigue resistance is critical.
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| 3. |
- Chen, Zhe, 1987-
(författare)
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Surface Integrity of Broached Inconel 718 and Influence of Thermal Exposure
- 2014
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Inconel 718 is a nickel-based superalloy that is extensively used as a disc material in gas turbine engines. The service life of gas turbine discs is normally governed by the modes of material degradation and fatigue failure since they work mostly at high temperatures and are subjected to cyclic mechanical loadings. Fatigue failures often start with the initiation of cracks at the surface and the precise details of the failure process significantly depend on the surface conditions. In turbine disc production, one of the last manufacturing steps is to broach root fixings, commonly of fir-tree design, for blade mounting. It has always been a challenge when machining Inconel 718 due to its high strength retention at elevated temperatures, rapid work hardening, as well as low thermal conductivity. This usually leads to rapid tool wear, and consequently shorter tool life, and at the end to the deterioration of the surface integrity of the machined components.The aim of this licentiate thesis is to increase our knowledge about the surface integrity, especially microstructure and residual stresses, of broached Inconel 718 and its stability under thermal exposure. This knowledge can later be used for analyzing the initiation and propagation of fatigue cracks in broached Inconel 718, particularly in the case of high temperature fatigue, thereby giving a better understanding of the failure mechanism of gas turbine discs from a fatigue point of view.A broaching operation has been performed using similar cutting conditions as that used in turbo machinery industries for producing fir-tree root fixings. In addition, service damages were analyzed in a retired dis of Inconel 718. Surface defects, severe plastic deformation and generation of high tensile residual stresses have been found to be the main damages to the surface integrity caused by the broaching operation. The machining induced plastic deformation was found to accelerate the microstructural degradation beneath the broached surface when subjected to thermal exposure. The surface tensile residual stresses can be completely removed after short thermal exposure, the tensile layer in the sub-surface region, however, exhibited a high resistance to stress relief at high temperatures. The damage analysis on the retired disc indicated that presence of the highly deformed layer on the machined surface is negative for preventing the occurrence of fretting fatigue in turbine discs.
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| 4. |
- Persson, Henrik, et al.
(författare)
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Modelling tool life in high speed machining of AD730
- 2018
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Ingår i: Procedia Manufacturing. - : Elsevier BV. - 2351-9789. ; 25, s. 316-321, s. 316-321
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Tidskriftsartikel (refereegranskat)abstract
- AD730® is a new type of nickel-based superalloy, developed by Aubert & Duval, with high temperature properties exceeding conventional superalloys such as Alloy 718. This paper presents the tool life model for this superalloy for the purpose of process optimization and manufacturing cost estimation. The tool life modelling is based on comprehensive machining tests, using the Colding model. The cutting tool material used is CBN 170, a grade specially designed and optimized for machining of nickel-based superalloys.
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| 5. |
- Zhou, Jinming, et al.
(författare)
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Comparative assessment of the surface integrity of AD730® and IN718 superalloys in high-speed turning with a CBN tool
- 2019
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Ingår i: Journal of Manufacturing and Materials Processing. - : MDPI AG. - 2504-4494. ; 3:3
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Tidskriftsartikel (refereegranskat)abstract
- Nickel-based superalloys are typical materials used in components of aeroengines and gas turbine machinery. The strength properties of these alloys at high temperatures are crucial not only to the performance (e.g., power generation efficiency, energy consumption, and greenhouse gas emissions) of aeroengines and industrial gas turbines, but also to machinability during component manufacturing. This study comparatively evaluated the surface integrity of two superalloys, AD730® and Inconel 718 (IN718), during high-speed finishing turning using cubic boron nitride (CBN) tools. IN718 is a conventional superalloy used for the hot section components of aeroengines and industrial gas turbines, while AD730® is a novel superalloy with enhanced high-temperature mechanical properties and good potential as a next-generation superalloy for these components. High-speed turning tests of two superalloys were conducted using a CBN cutting tool and jet stream cooling. The achieved surface integrity of the AD730® and IN718 superalloys was characterized and analyzed to assess the comparability of these alloys.
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