Papers by Keyword: Nickel-Based Alloy

Abstract: Nickel-based alloy is known as one of the most difficult–to-machine materials and the milling process is one of the most common metal removal operations. Modeling and simulation of milling process have the potential for understanding the milling mechanism, improving cutting tool designs and selecting optimum conditions, especially in advanced applications such as high-speed milling. This paper presents a 3D coupled thermo-mechanical finite element model based on ABAQUS\Explicit for the simulation of Inconel 718 chip formation in metal cutting. In the simulations, a Lagrangian formulation with an explicit solution scheme and a penalty contact algorithm has been used. The material behavior is modeled with classical Johnson-cook plasticity constitutive model and dynamic failure criteria for element removal, coupled with adaptive meshing and mass scaling technology for limiting the calculation time. The milling tool is modeled in UG software according to the real tool geometry, and meshed as a rigid tool. In order to verify the accuracy of 3D simulation, results (cutting forces and cutting temperature) were compared with the experimental results under the same cutting conditions as the simulations. The results obtained indicate that the simulation methodology is capable of predicting the cutting forces and cutting temperature. It suggests that 3D finite element simulation model of cutting processes can be truly trusted.

Abstract: An experimental study was undertaken to explore the conditions and performance on rough and finish grinding fir-tree root forms of turbine blades made of a nickel-based alloy using vitrified CBN wheels and water-based grinding fluid. This work was motivated by switching the grinding of fir-tree root forms from grinding with conventional abrasive wheels to vitrified CBN wheels for reducing overall production cost and enhancing productivity. Grinding experiments were conducted to measure grinding forces, power, surface roughness, and stress near the blade roots under various dressing and grinding conditions. Wheel re-dressing life in terms of the total number of good parts ground between dressing was tested with the condition producing the maximum material removal rate while satisfying preset part quality and process requirements. It was found that the maximum material removal rate achievable in rough grinding was restricted by the stress limit and the wheel re-dressing life was dominated by the radial wheel wear limit. The targeting part quality and process requirements were achieved. It was proved that vitrified CBN grinding process is feasible and very promising to machine fir-tree root forms.

Abstract: Wetting behaviors of pure nickel and nickel-based alloys on sintered silicon carbide ceramics and their interfacial microstructures were investigated in this presentation. The nickel-based alloys were mainly the commercial nickel-molybdenum-chromium products. The wetting and spreading properties were observed by a real-time thermal optical measurement system under flowing argon-5%hydrogen atmosphere. As temperature increased, the pure nickel cylinder sample had few changes before 1356°C except for the thermal expansion in size and changed to liquid drop-shape when the temperature reached 1366°C. The contact angle was about 90^o. And nickel could not contact sintered silicon carbide ceramics well. However, the introduction of molybdenum and/or chromium in the pure nickel was good for the wetting properties of pure nickel on sintered silicon carbide ceramics. The contact angles of nickel-based alloys (B-1, C-1 and C-2) on sintered silicon carbide ceramics after holding 15min at 1400°C were 25^o, 12.5^o, 11.5^o, respectively. And they hardly reduced as temperature increased. The SEM images indicated that the interfacial microstructures of B-1 and C-1 on sintered silicon carbide ceramic substrates were uniform and the dissolved interface near silicon carbide ceramics indicated that they had a good bonding. At the same time, the reciprocal diffusion was clear in the intermediate layer. Besides that, the introduction of chromium was supposed to reduce the diffusion rate of molybdenum from the alloy to the ceramic substrate.

Abstract: In production of safety critical components in aero engine manufacture, to date broaching is the most efficient process machining fir-tree slots in turbine discs. Machining highly thermal resistant Nickel-based alloys, manufacturers commonly use High Speed Steel (HSS) tools and work at low cutting speeds in order to stay at rather low tool wear rates and avoid part quality defects. The key variable affecting tool wear as well as part quality, as in most machining processes, is the temperature. Excessive temperatures in the cutting zone lead to enhanced tool wear on the one hand, and surface defects such as white layer formation and residual tensile stresses on the other hand. In this article, the temperature development is investigated for typical tool geometries and cutting parameters in broaching. Furthermore, the possibility of a temperature control using intermediate variables such as process forces is discussed, and potentials employing a control are explained.

Abstract: This paper presents an experimental investigation of the machining characteristics of IN718 nickel-based super alloy in wire electrical discharge machining (WEDM) process. During experiments, parameters of discharge current and pulse on time were changed to explore the effect on various aspects of the surface characteristic. Scanning electron microscopy (SEM), surface roughness and micro hardness tests were performed. Experimental results reveal that the surface roughness will increase with the increasing of current and pulse duration. Micro hardness tests show there is no hard phenomenon.

Abstract: The technology to produce micro-holes without recast layer on nickel-based alloy is studied in this work. The holes are firstly drilled with Nd: YAG laser, a millisecond pulsed laser of high power and efficiency. For the reason of thermal effect, however, holes drilled by this laser always have the defect of recast layer, which is a serious problem, especially in the application as aviation and aerospace engine. In order to remove the recast layer, laser parameters are optimized to produce micro-holes with the least recast layer, and then a kind of chemical etching is used to clear the residual recast layer completely.

Abstract: An experimental study is reported on the grinding of a nickel-based alloy using vitrified CBN wheels. This work was motivated by switching the grinding of fir-tree root forms of jet engine blades from creep-feed grinding with conventional abrasive wheels to vitrified CBN wheels. The objective is to explore process limits and practical grinding parameters for judging the switch in terms of overall costs and productivity. Straight surface grinding experiments were conducted with water-based fluid on rectangular blocks at a fixed wheel speed v_s = 45 m/s, various depths of cut a = 0.05 - 1.0 mm, and workspeeds v_w = 2 - 40 mm/s. Grinding power, forces, surface roughness, and radial wheel wear were measured. Specific material removal rate of 8 mm³/(mm.s) was reached in rough grinding using a wheel dressed for achieving surface roughness R_a = 0.8 µm in finish grinding. It was found that shallow depths of cut combined with fast workspeeds, or less creep-feed modes, are more suitable for achieving high material removal rates with vitrified CBN grinding. Rough grinding is restricted by high grinding temperatures with newly dressed wheels and by chatters with worn wheels.

Abstract: According to the microstructure defects of laser claded nickel alloy, such as crack and nets brittle phase, the friction stir processing (FSP) method is utilized in this paper to modify microstructure defects by the coupled effect of thermal and stress of FSP. For this purpose, two key scientific problems of large deformation condition and microstructure evolution theory during FSP, are proposed in this paper. Based on this, the following issues are highlighted in this work. Firstly, obtain the friction condition of larger deformation by continuous dirved friction experiment. Secondly, study on the temperature (T), stress (σ), and strain velocity under different processing parameters via self-developed physical simulation apparatus. Thirdly, disclose the effects of T、σ、 on the microstructure evolution and then obtain the microstructure evolution equation by dynamic re-crystallization. The above work could provide theory support for the new technique of laser cladding and FSP for preparing high performance coating.

Abstract: To analysis cutting mechanism and heat transfer coefficient of Ni-based superalloy IN718, this paper introduced a three-dimensional finite element model for cutting process based on DEFORM-3D V6.1, and cutting force Fy and cutting temperature T under different feed rate f , cutting speed v and back engagement ap were obtained. The temperature variation during cutting process under different cooling method was analyzed. The simulation results indicate that the influence of back engagement ap on the cutting force Fy is the greatest, while that of cutting speed v is minor; and for cutting temperature T, influence of cutting speed v is the greatest, while that of back engagement ap is minor. Influence of heat transfer coefficient on highest temperature and average cutting force Fy is minor, but its influence on average temperature is quite obvious. Greater heat transfer coefficient is less average temperature.

Abstract: The mechanical engineering industry is always in the search of new hardfacing alloys which nowadays make it possible to solve considerable delicate problems of abrasive wear and corrosion. These alloys are heterogeneous materials and are generally composed of a ductile matrix and a significant proportion in hard phases (carbides, borides or silicides), which give a good wear resistance and corrosion. The following studies made on alloys containing Ni, rich in Silicon and tungsten. We noted that addition of these elements (Si and W) got interesting mechanical properties. The alloys that we chose for this study contain the elements C, B, Si, Cr and W with additions in Ti and Mo. The aim of this work is the characterisation of the various phases formed during solidification, to study chemical affinities in this system poly-constitutes and to make a correlation between the chemical composition, the conditions of development and the microstructures obtained.