Showing papers on "Inconel published in 2003"

Effect of standard heat treatment on the microstructure and mechanical properties of hot isostatically pressed superalloy inconel 718

Abstract: Ni–Fe base superalloy, Inconel 718, was processed through powder metallurgy (P/M) hot isostatic pressing (HIP) route. In order to balance the strength and ductility, the HIPed material was given the standard heat treatment, viz. solution treatment at 980 °C for 1 h/water quenched (WQ) to room temperature and a two-step ageing treatment consisting of 720 °C for 8 h/furnace cooling (FC) at 55 °C h−1 to 620 °C and holding at 620 °C for 8 h before air cooling (AC) to room temperature. Optical microscopy and scanning electron microscopy (SEM) studies on the heat treated alloy have shown a homogeneous microstructure with fine grain size (25 μm) along with the presence of prior particle boundary (PPB) networks. Transmission electron microscopy (TEM) on the heat treated material has revealed the presence of oxides, MC carbides and δ-precipitates at the grain boundaries and a uniform precipitation of fine γ″ and γ′ strengthening phases in the matrix. Tensile and stress rupture tests were performed on the heat treated material. While the yield strength (YS) and ultimate tensile strength (UTS) of the HIPed and heat treated alloy at room temperature and 650 °C were comparable to those of conventionally processed wrought IN 718, its ductility was lower. The stress rupture life of the HIPed alloy improved marginally due to heat treatment and met the minimum specification requirement of life hours but the rupture ductility was found to be inferior to that of the wrought material. The fractography of the failed samples has revealed the transgranular ductile mode of fracture in the as-solution treated alloy, while intergranular mode of failure with the decohesion of PPBs occurred more predominantly in the aged condition. This change of fracture mode with ageing treatment shows the ductility dependence on the relative strength of the matrix and PPBs. The TEM studies on the deformed alloy have revealed that the brittle oxides and carbides at the prior particle boundaries coupled with the fine γ″ and γ′-precipitates in the matrix are responsible for low ductility at 650 °C. The investigations of the present study have led to better understanding of the structure–property relationships in HIP+heat treated alloy 718 and suggest that the standard heat treatment recommended for wrought IN 718 is not suitable for HIPed alloy and has to be modified to realise optimum properties.

Deposition, characterization and machining performance of multilayer PVD coatings on cemented carbide cutting tools

Abstract: CrN/TiN and TiN/AlTiN multilayer coatings with different periods were deposited on cemented carbide cutting tools in an industrial-size cathodic arc evaporation device Nanolayer coatings were particularly studied and the influence of the superlattice period on mechanical behaviors have been investigated Mechanical properties were first correlated to the period of multilayer and nanolayer coatings Machining performance of coated cutting tools were then evaluated by turning Inconel 718 superalloy The decrease of layer periodicity leads to higher microhardness for both compositions Adhesion tests and surface topography analyses indicate better adhesion and lower roughness for CrN/TiN than for TiN/AlTiN coatings All these coatings, especially TiN/AlTiN nanolayers, favorably influence flank wear and cutting time for machining Inconel 718 in relatively severe cutting conditions The relationship between physical properties, coatings compositions and wear mechanisms during machining Inconel 718 is discussed

Measurement of Specific Heat Capacity and Electrical Resistivity of Industrial Alloys Using Pulse Heating Techniques

Abstract: The determination of the specific heat capacity and electrical resistivity of Inconel 718, Ti-6Al-4V, and CF8M stainless steel, from room temperature to near the melting temperatures of the alloys, is described. The method is based on rapid resistive self-heating of a solid cylindrical specimen by the passage of a short-duration electric current pulse through it while simultaneously measuring the pertinent experimental quantities (i.e., voltage drop, current, and specimen temperature). From room temperature to about 1300 K, the properties are measured using an intermediate-temperature pulse-heating system by supplying a constant current from a programmable power supply and measuring the temperature using a Pt-Pt:13% Rh thermocouple welded to the surface of the specimen. From 1350 K to near the melting temperatures of the alloys, the properties are measured using a millisecond-resolution high-temperature pulse-heating system by supplying the current from a set of batteries controlled by a fast-response switching system and measuring the temperature using a high-speed pyrometer in conjunction with an ellipsometer, which is used to measure the corresponding spectral emissivity. The present study extends the application of these techniques, previously applied only to pure metals, to industrial alloys.

High temperature carbon corrosion in solid oxide fuel cells

Abstract: Operating conditions in a current design for a planar geometry oxide fuel cell plant are briefly reviewed and the danger of encountering “metal dusting” conditions identified. Laboratory tests were designed to produce accelerated metal dusting by exposing heat resisting alloys to a CO–26 H2–6 H2O (vol. pct) gas mixture at 680°C under thermal cycling conditions. The hot gas composition corresponded to ac = 2.9 and an oxygen potential high enough to oxidise chromium and aluminium, but not iron or nickel. The alloys tested included ferritic and austenitic chromia formers and two ferritic alumina formers, all with electropolished surfaces. Thermal cycling of the chromia formers led to oxide scale damage followed by internal carburisation, metal dusting and coking. This failure occurred very rapidly on most austenitic materials (Alloy 800, Inconel 601, 690, 693, Alloy 602CA), but did not commence until after approximately 50 one-hour cycles for the ferritic steel Fe–27Cr–0.001Y (wt %). The alloy with t...

Joining alumina to inconel 600 and UMCo-50 superalloys using an Sn10Ag4Ti active filler metal

Abstract: Alumina ceramics were brazed to Inconel 600 and UMCo-50 superalloys at 900 °C for 10 min using an Sn10Ag4Ti active filler metal. The brazing filler showed good wettability on alumina and superalloys. The flexural strengths were 69 and 57 MPa for alumina/Inconel 600 and alumina/UMCo-50 joints, respectively. In both cases, the brazed specimens fractured along the Sn10Ag4Ti/superalloy interfaces after four-point bending tests. Electron probe microanalysis (EPMA) elemental mapping revealed that the Ni of Inconel 600 and the Co of UMCo-50 dissolved into Sn10Ag4Ti filler metal, which serves to reinforce the weak Sn10Ag4Ti matrix.

The Effect of PWHT on the Material Properties and Micro Structure in Inconel 625 and Inconel 725 Buttered Joints

Abstract: This report describes investigations performed on as welded and post weld heat treated samples of AISI 8630 steel, buttered with Inconel 625 and Inconel 725. The investigations have focused on the properties and microstructure in the partial mixed zone between the buttering and the steel before and after post weld heat treatment. The samples were heat treated for 4 1/2 hours at 640°C, 665° and 690°C and investigated with respect to mechanical properties and microstructure near the fusion line. A range of testing and analyses were performed including notch impact toughness testing, identification of fracture initiation and propagation in impact specimens, hydrogen measurements, examination of the micro structure in steel and Inconel using light microscope, hardness testing and electron micro-probe analysis of the alloying elements across the fusion line. Additional investigations in TEM on samples from an actual joint, post weld heat treated at 665°C were also performed. The results show that post weld heat treatment at 665°C and 690°C reduced the impact toughness in coarse grained heat affected zone, caused by decarburisation, ferrite formation and grain growth. The partially mixed zone (5–10μm) of the Inconel buttering, gained partly extremely high hardness caused by carbon enrichment, reaustenitization and formation of virgin martensite. As welded samples gave more favorable properties and microstructure than the post weld heat treated ones.Copyright © 2003 by ASME

Characterisation of hot isostatically pressed nickel base superalloy Inconel* 718

Abstract: Inert gas atomised Inconel 718 superalloy powder was characterised for various important properties and subsequently consolidated by hot isostatic pressing (hipping) at 1200° C and 120 MPa for 3 h. The density of the as compacted material was nearly the same as its theoretical density. Optical microscopy of as hipped material showed a fine grained structure with no porosity but having annealing twins and prior particle boundaries (PPBs). Electron probe microanalysis (EPMA) studies revealed that the PPBs were decorated with Al, Ti oxides, and MC type carbides enriched with Nb and Ti. In addition to these phases, the presence of very fine γ"-Ni3Nb and γ'-Ni3(Al,Ti) precipitates in the matrix were revealed by TEM analysis, which indicates that the compacted material was partially aged during the slow cooling stage of hipping. Tensile tests conducted on the as hipped material showed that the ultimate tensile strength (UTS) and ductility values were comparable to those obtained in the (solution treated...

Laser powder fusion repair of Z-notches with nickel based superalloy powder

Abstract: A method is provided for repairing Z-notch wear surfaces on low pressure gas turbine engine turbine blades. The method is directed to turbine blades made of superalloy Inconel 713. Powdered Inconel 713 is welded to the Z-notch wear surface by directing an Nd:YAG laser beam upon the material. The laser beam is focused and traverses the wear surface in a stich-like pattern. The method allows Inconel 713 turbine blades to be repaired with the same material in a manner that does not generate cracking in the matrix material.

Reactive magnetron sputtering as a way to improve the knowledge of metastable f.c.c. nitrogen solid solutions formed during plasma assisted nitriding of Inconel 690

Abstract: Low temperature plasma assisted nitriding (PAN) treatments of Inconel 690 (a nickel base alloy with a 30 wt.% chromium content) produce a complex layer constituted by two different metastable f.c.c. solid solutions denoted (γN1 and γN2). In addition, different layer thicknesses are observed for differently oriented grains. Reactive magnetron sputtering (RMS) of Inconel 690 in argon–nitrogen containing mixtures is used to produce homogeneous films constituted by a well defined γN phase. In reactive conditions, the as-deposited coatings (T<100 °C) containing up to 30 at.% of nitrogen are nanocrystalline supersaturated f.c.c. solid solution (γN) with a grain size lying between 3 and 7.5 nm. A comparison between the products synthesized by these two techniques (PAN and RMS) is presented in this study. The formation of γN phases in low temperature PAN is discussed in the light of electron backscatter diffraction measurements and by comparison with X-ray diffraction patterns of RMS coatings. By using the results obtained in situ by RMS on heated substrates and by tempering of as-deposited films, the decomposition products of the γN phase at high temperature (⩾450 °C) or long PAN treatments at 400 °C are identified to be f.c.c. CrN and γ(Ni,Fe) depleted in nitrogen.

High temperature moiré interferometry investigation of creep crack growth of inconel 783—environment and β-phase effects

Abstract: The effect of β-phase and environment on creep crack growth behavior of Inconel 783, the newly developed low thermal expansion superalloy, was investigated using high temperature moire interferometry. Results show that oxygen partial pressure plays an important role on the creep crack growth behaviors of the alloy. Stress assisted grain boundary oxygen (SAGBO) embrittlement is the principal mechanism of the environmental degradation of the alloy. β-Phase network along the grain boundaries of the alloy improves the resistance to creep crack growth by improving the ductility of the alloy and preventing the occurrence of SAGBO embrittlement.

Temperature, microstructure and mechanical response during shear-band formation in different metallic materials

Abstract: Adiabatic shear banding was investigated in low carbon steels, a nickel-base superalloy Inconel 718. Tests were performed using cylindrical as well as flat hat-shaped specimens in a Split-Hopkinson-Pressure-Bar set-up. The flat specimen allows the in situ measurement of the temperature field by means of a fast infrared detector array simultaneously with the mechanical response of the specimen. Two types of arrays (InSb and InGaAs) were used in the localization and postlocalization phase, respectively, where the temperatures lie in different ranges. Special interest is given on the development of the localization process from the early stage up to well-developed bands and/or failure. The microstructural changes were investigated in these stages using optical microscopy, SEM and TEM. The summarized result of all observations is that the shear bands (white bands in steel and similar but much thinner bands in Inconel 718) were formed during the postlocalization phase by friction processes obviously.

An investigation of the micromechanisms of fatigue crack growth in structural gas turbine engine alloys

Abstract: This paper presents an overview of fatigue fracture modes in selected structural alloys employed in gas turbine engines. These include the mechanisms of fatigue crack growth in the near-threshold, Paris and high-ΔK regimes obtained from Ti-6Al-4V, Inconel 718 and PWA 1472 (a single crystal nickel-based superalloy of similar chemical composition to Inconel 718). Fatigue fracture modes in these materials are shown to be strong functions of the stress intensity factor range, ΔK, and the maximum stress intensity factor, K max. Fatigue mechanism maps are also presented to show the parametric ranges of ΔK and K max corresponding to the different fatigue fracture modes.

Effect of High-Pressure Coolant Supplies when Machining Nickel-Base, Inconel 718, Alloy with Ceramic Tools

Abstract: Chip breakability is significantly improved with the use of high pressure coolant supply. This is a result of the reduction in the tool-chip contact length during machining as the coolant under high pressure lifts the chip up after passing the deformation zone. Increasing the coolant pressure results in shorter ceramic tool life when machining Inconel 718 suggesting that the high pressure coolant supply reduces temperature at the cutting zone below a critical level where ceramic tools can perform satisfactorily. The inadequate fracture toughness of ceramic tools makes them more susceptible to failure by mechanical action such as notching at the depth of cut line and premature fracture. The notch wear rate increases with higher coolant supply pressure due to significant erosion of the tool material by the high pressure coolant jet. This mechanically related failure mode occurs on a random basis leading to inconsistency in tool performance, accelerated by fluctuations in thermal and mechanical properties wh...

Fatigue Properties of Inconel 718 in Long Life Region at Elevated Temperature

Abstract: The fatigue properties of Inconel 718 in long life region up to 10 8 cycles were investigated under rotating bending at room temperature and 500°C. The early propagation of a crack was suppressed by oxide induced crack closure. Consequently, fatigue strength was higher at 500°C than at room temperature. Surface fracture occurred at high st ress levels and internal fracture occurred in long life region beyond 10 7 cycles at 500°C. Correspondingly, S-N curve at 500°C presented in a step-wise shape, compared to the conventional one-step sha pe at room temperature. Intergranular cracking was observed at the origins of internal fracture at 500°C. Introduction Nickel-base superalloy has been widely used in the severe conditions such as components of jet engines, gas turbine engines and so on, because this alloy has excellent proper ties in st ength at high temperature and high resistance to corrosive environment. Therefore, ma ny studies have been carried out on the mechanical properties, especially on the creep and fatigu e properties [1-4]. On the other hand, the fatigue properties of high strength steels and surfa ce modified steels in the long life region beyond 10 7 cycles, are of much interest to machine designers and mater ial engineers. For example, origins of fatigue fracture in high strength steels ch ange from the surface slips or defects in short life region to the interior in long life one, correspondingly S-N curve shows a step-wise shape [5-9]. Moreover, the presence of fatigue limit is not clarifi ed. Therefore, the accumulation of experimental data and the establishment of criteria for design and maintenance of machines and structures are urgent subjects for materials employed under the c ircumstances where high strength steels and surface modified steels find increasing applications. However, the data on the fatigue properties in these materials in long life region, especially t elevated temperature, were very limited [10]. In the present study, the fatigue properties of Inconel 718 in long life region up t 10 cycles were investigated under rotating bending at room temperature and 500°C. Key Engineering Materials Online: 2003-07-15 ISSN: 1662-9795, Vols. 243-244, pp 321-326 doi:10.4028/www.scientific.net/KEM.243-244.321 © 2003 Trans Tech Publications Ltd, Switzerland All rights reserved. No part of contents of this paper may be reproduced or transmitted in any form or by any means without the written permission of Trans Tech Publications Ltd, www.scientific.net. (Semanticscholar.org-13/03/20,21:06:00) Material and Experimental Procedures The material used was a nickel-base superalloy Inconel 718. The ch emical compositions (wt%) of the alloy are 0.03C, 0.05Si, 0.06Mn, 0.008P, 0.002S, 18.5Cr, 3.08Mo, 0.27Co, 0.02Cu, 0.55Al, 0.96Ti, 19.18Fe, 0.004B, 5.03Nb, and Ta and remainder Ni. The alloy was solution tre ated at 982°C for 1 hr, water quenched, then aged at 720°C for 8 hr, furnace cooled to 621 °C and aged at 621°C for 8 hr followed by air cooling. The mean grain size was about 10 m. The 0.2% proof stress and ultimate strength of the alloy after heat treatment were 1 147 MPa and 1372 MPa at room temperature and 1050 MPa and 1250 MPa at 500°C, respectively. Figure 1 shows the shape and dimensions of specimen. Prior to fatigue testing, all the specimens were electro-polished to removed the work hardened surface layer by about 20 m. The crack length was measured along the circumferential direction on the surfac e using the plastic replica method. The measurement of crack length at 500°C was performed by interrup ting the test machine at specified intervals of stress repetitions, then cooling down the spe cimen to take plastic replicas. The influence of the repetitious heating and cooling processes on the fat igue life was hardly recognized. The tests were carried out at room temperature and 500°C using a high temperature Ono type rotating bending fatigue test machine with a capacity of 100 N·m, operating at 55Hz.

Evaluation of effects of niobium and manganese addition on nickel base weldments

Abstract: The present work investigates the influence of different concentrations of Nb (from 01 to 335 wt-%) or Mn (from 078 to 332 wt-%) on the microstructure and mechanical properties of an Inconel 690 weldment Welding electrodes are produced by coating Inconel filler metal 52 with a flux containing various percentages of Nb or Mn Weldments with a bevel edge are butt welded via a manual shielded metal arc welding process, using identical parameters and procedures The microstructure and mechanical properties of the resulting weldments are then analysed The experimental results indicate that the subgrain structures of the welds are primarily dendritic Under tensile testing, it is found that each specimen ruptures in the fusion zone and that the fracture surfaces exhibit entirely ductile features It is noted that as the content of Nb increases, the welds tend to show a finer subgrain structure, ie having smaller dendritic spacing Consequently, the tensile strength and microhardness of the fusi

Metallurgical changes and mechanical behaviour during high temperature aging of welds between Alloy 800 and 316LN austenitic stainless steel

Abstract: In the use of ferritic to austenitic stainless steel transition joints for power plant applications, the difference in coefficients of thermal expansion constitutes a serious problem. One way to mitigate this is to use a trimetallic configuration by interposing a material with a coefficient of thermal expansion intermediate between the ferritic and austenitic steels. Modified 9Cr - 1Mo steel has been joined to 316LN austenitic stainless steel using Alloy 800 as an intermediate piece. In the work herein reported, welds between Alloy 800 and 316LN have been produced using Inconel 182 filler material. These have been subjected to high temperature exposure for up to 5000 h at 625 ° C. Results have shown that up to 500 h of aging the structure and mechanical properties remain unaffected. On treatment for 2000 and 5000 h, however, there is a noticeable increase in hardness and reduction in toughness. These have been found to be caused by precipitation of Ni3Ti and carbide phases including NbC and M23C6.

Microstructure development and superplasticity in Inconel 718 sheet

Abstract: Within the range of temperatures and strain rates investigated, mechanical testing identified the optimum forming condition for Inconel 718 sheet as being 965°C with a strain rate of 10-4 s-1. A detailed investigation of the microstructural behaviour under these deformation conditions was carried out and is reported here. Typically superplastic deformation would generate an enhanced rate of grain growth. This was not the case with the present material; instead it was found that a slight apparent grain size reduction occurred and there was evidence of substantial dislocation activity. It was concluded that the material was deforming on the borderline between 'true' superplasticity and normal slip based deformation.

Effect of a localized thermal treatment process on the electrochemical behaviour of thermally sprayed nickel-based alloy

Abstract: In present work, thermally sprayed Inconel 718 coatings were prepared by high velocity oxy-fuel (HVOF) spraying. To promote their corrosion resistance the effect of different associated processes (AP) to the torch have been investigated. The first one is a pre-heating maintained during the coating elaboration. The second one consists in a post-cooling process applied just after particle impingement on the substrate. The third one corresponds to an association of a pre-heating and post-cooling process to the thermal spraying torch to elaborate coatings. In each case, the associated processes were maintained during coating elaboration. Coatings were characterized by their metallographic microstructures, phase compositions, microhardness and fractal dimensions of their cross-section profiles. The electrochemical properties of the coatings were evaluated in sulfuric acid solution using free potential measurements and polarization curves. It was found that the cross-section profiles and the lamellar morphologies of the coatings prepared using the different combinations of pre-heating or post-cooling processes were similar to each other. However, the additional pre-heating process used with torch has notably improved the corrosion resistance of the coating opposite to the post-cooling process. These coatings were all preferentially corroded around the lamellar boundaries at the surfaces. The corrosion resistance can be related to the oxide contents in the thermally sprayed coatings and the different chromium contents around their lamellae boundaries due to the chromium depletion during the particle oxidation step. The heat–cooling process presented in this paper seems to have the same effect that the pre-heating process.

Ultra-supercritical steam corrosion

Abstract: Efficiency increases in fossil energy boilers and steam turbines are being achieved by increasing the temperature and pressure at the turbine inlets well beyond the critical point of water. To allow these increases, advanced materials are needed that are able to withstand the higher temperatures and pressures in terms of strength, creep, and oxidation resistance. As part of a larger collaborative effort, the Albany Research Center (ARC) is examining the steam-side oxidation behavior for ultrasupercritical (USC) steam turbine applications. Initial tests are being done on six alloys identified as candidates for USC steam boiler applications: ferritic alloy SAVE12, austenitic alloy Super 304H, the high Cr- high Ni alloy HR6W, and the nickel-base superalloys Inconel 617, Haynes 230, and Inconel 740. Each of these alloys has very high strength for its alloy type. Three types of experiments are planned: cyclic oxidation in air plus steam at atmospheric pressure, thermogravimetric analysis (TGA) in steam at atmospheric pressure, and exposure tests in supercritical steam up to 650oC (1202°F) and 34.5 MPa (5000 psi). The atmospheric pressure tests, combined with supercritical exposures at 13.8, 20.7, 24.6, and 34.5 MPa (2000, 3000, 4000, and 5000 psi) should allow the determination of the effect of pressure on the oxidation process.

Hole drilling of Inconel 718 by high intensity pulsed ultraviolet laser

Abstract: Holes were percussion drilled in Inconel 718 plates by a high intensity pulsed ultraviolet laser (266 and 355 nm) with 8 ns pulse width. It showed that shortening the laser wavelength resulted in thinner recast layers, less microcracks, and faster machining speed. In order to get high quality and fast speed in laser hole drilling, a two-step processing method was proposed and tested.