Papers by Keyword: Inconel 718

Abstract: Laser based metal additive manufacturing (AM) is an emerging technology in various aerospace industries including aero-engine components and turbine manufactures. Laser cladding is a potential process for material deposition and surface enhancement technique that forms a strong metallurgical bond with the substrate. In the present study, Nickel based Inconel 718 (IN718) super alloy which maintains high strength working at elevated temperatures is used as the clad material. The study investigates the processing of Inconel 718 with powder morphology and microstructural properties and also two, three and four-layer deposition. This study explores the possibility of depositing IN718 using laser cladding that can be better considered as metal AM process.

Abstract: In this work, an experimental measurement, contour method, is implemented for an after quenching IN718 forging specimen to obtain the distribution of residual stress field. A sequentially coupled thermal mechanical finite element model is developed with the similar 3D geometry of the experimental specimen and implemented the same heat transfer boundary of the rapid quenching with the experimental condition. A thermal mechanical rate dependent continuum plasticity model for IN718 alloy, with the dynamic strain ageing (DSA) effect incorporated, is developed to study the impact of DAS effect on the evolution of residual stress during rapid quenching. The modelling predictions of residual stress are in good agreement with the contour method measurements. The impact of DSA effect is further quantified, indicating that an annular high plastic strain rate region in the core part of the disc is captured during the simulation of the quenching process.

Abstract: INCONEL 718 superalloy (IN 718) is frequently used in highly aggressive environments, such as aerospace and gas turbine engines, where excellent mechanical properties, creep-, fatigue- and oxidation-resistance performance at high and cryogenic temperatures are required. Recent studies have successfully cold sprayed IN 718, showing great potential mainly in maintenance and repairing fields. However, due to the low plastic deformation, the manufacture of IN 718 cold sprayed coatings often requires the use of expensive propulsive gases or high working parameters to enhance deposition efficiency, with a significant increase in production costs. This paper investigates for the first time the addition of Ni to IN 718 powders in order to increase plastic deformation and interparticle bonding strength. Four composite coatings were deposited via a high-pressure cold spray process using nitrogen as propulsive gas, considering different IN 718 mass fractions in the feedstock: C1 (0 wt%), C2 (25 wt%), C3 (50 wt%), C4 (75 wt%). The coatings are examined in terms of microstructural characteristics and tribological performance. The addition of IN 718 particles significantly improves the mechanical properties of the coatings, despite an increase in porosity, which however does not exceed 1%. The tribological performance of the four coatings is investigated using a pin-on-disk test, demonstrating that the coating wear resistance behaviour improved as the IN 718 content increased. Analysis of the wear mechanism shows that C4 coating has a different wear behaviour than the other coatings, thus achieving the best wear-resistance performance.

Abstract: Challenging structural applications such as customized jet engine parts are increasingly fabricated by Selective Laser Melting (SLM) of Inconel 718 powder. The as-built surface quality of SLM parts is however inferior of the machined version and the fatigue behavior is negatively affected. The as-built fatigue response of SLM Inconel 718 was quantified here using three sets of directional specimens. Since the surface quality is influenced by powder characteristics, process parameters and layer-wise fabrication, fatigue results showed a directional contribution that was interpreted using metallography and fractography.

Abstract: The spacer grids are part of the Fuel Element (FE) set of the PWR (Pressurized Water Reactor) type reactor. These grids maintain the position of the fuel rods within the arrangement of the FE, conserving among them the spacing necessary for the operation of the reactor. The grids are manufactured from the union of the intersecting points of stamped strips of Base Material (BM) Inconel 718, by a joint process called brazing. The addition metal (AM) used consists of a brazing paste based on Ni-Cr-P (nickel-chromium-phosphorus), which is added dropwise in the intersection of grids with a clearance of 0.025 mm. For this purpose, Inconel 718 smooth strips of 0.35 mm thick nickel plated samples were prepared, the AM was added and the vacuum oven was 10^-3 mbar, in different time and temperatures. The samples were prepared by metallography and characterized using optical microscopy (OM), scanning electron microscopy (SEM) and mechanical microhardness test. The purpose of this work is to characterize the brazing joint by means evaluate the size of precipitates and the different compounds formed in the joint. It was found different precipitates composed mainly of titanium and niobium. Phosphorus rich phases were found in the brazed region. The mean hardness of the BM was 469 ± 12 HV and in the joint region hardness of 1345 ± 34 HV was found in the lighter phases.

Abstract: Machining is one of the major manufacturing processes that converts a raw work piece of arbitrary size into a finished product of definite shape of predetermined size by suitably controlling the relative motion between the tool and the work. Lately, machining process is shifting towards high speed machining (HSM) from conventional machining to improve and efficiently increase production, and towards dry machining from excessive coolant used wet machining to improve economy of production. And the tools used are mostly hardened alloys to facilitate HSM. The work piece materials are continually improving their properties by emergence and development of newer and high resistive super alloys (HRSA). In this paper an attempt has been made to validate an experimental result of cutting force obtained by performing HSM on an HRSA Inconel 718, by comparing it with the numerical result obtained by simulating the same setting using DEFORM 3D software. Based on the comparison it is found that the simulated results exhibit close proximity with the experimental results validating the experimental results and the effectiveness of the software.

Abstract: The development of micro-products in industry, like aviation, medical equipment, electronics, etc, has been increasing lately. The need for scaling down of product has been increasing to make the product simpler and complex. Micro-milling has capabilities in producing complex parts. In this study, mapping and comparing the result of the machining process of Inconel 718 and Aluminum Alloy 1100 was employed. In this experiment, Inconel 718 was used as workpiece material and the result of Aluminum Alloy taken from recent studies. Then, A cutting tool with a diameter 1 mm carbide coating TiAlN was used in this experiment. The machining process was performed with three varieties of spindle speed and feed rate with a constant depth of cut. After the machining is done, the mapping of the result surface roughness of Inconel 718 and AA1100 performed. It was found that Inconel 718 has poor machinability compared with AA 1100. Inconel 718 also has a high manufacturing cost compared to AA 1100 because the cutting tool was easy to wear.

Abstract: Inconel 718 is a nickel-based super alloy well suited for high-temperature applications encountered in space shuttles, aircraft black box and turbocharger due to their inherent properties. Taking into account of extreme working conditions, efficiency in the process of machining without affecting the nature of the surface integrity with utmost care assumes a lot of importance. In this current study, an attempt has been made to investigate the influence of cutting speed and feed rate on various machining aspects like cutting forces, chip morphology, surface roughness and tool wear during the orthogonal turning of Inconel 718. Also, the work has been focused on feed forces and thrust forces to understand the proper material deformation behaviour and surface integrity.

Abstract: In this paper, preheating temperature was investigated for the laser assisted machining (LAM) of Inconel 718 under different conditions for the milling test. The experimental results show that the requirement of laser power for the particularly preheating temperature proportionally increased with the table speed. The resultant cutting force for sufficient shearing work material in LAM was lower than conventional machining (CM) approximately 11, 21 and 28% for the cutting speed of 30, 50 and 75 m/min, respectively. The tool wear in LAM could be improved at relatively high cutting speed of 75 m/min and the hardness of machined surface in LAM was slightly higher than CM.

Abstract: The ability to withstand axial hot compression at 700 °C of electropulsing-assisted ultrasonic surface rolling process (EUSRP) treated Inconel 718 was characterized by hot compression tests in this study. Results indicated that EUSRP induced ultra-fine microstructure on the near-surface regions of the sample and the formation of recrystallized ultra-fine grains in the near-surface regions was further promoted during hot compression test. In addition, a large number of nanoγ'' phases were precipitated on the broadened grain boundaries of the near-surface regions. In summary, EUSRP enhanced the ability to withstand axial hot compression of Inconel 718 at 700 °C.