Showing papers on "Inconel published in 1989"

INCONEL 718: A solidification diagram

Abstract: As part of a program studying weldability of Ni-base superalloys, results of an integrated analytical approach are used to generate a constitution diagram for INCONEL 718* in the temperature range associated with solidification. Differential thermal analysis of wrought material and optical and scanning electron microscopy, electron probe microanalysis, and analytical electron microscopy of gas tungsten arc welds are used in conjunction with solidification theory to generate data points for this diagram. The important features of the diagram are an austenite (γ)/Laves phase eutectic which occurs at ≈19.1 wt pct Nb between austenite containing ≈9.3 wt pct Nb and a Laves phase which contains ≈22.4 wt pct Nb. The distribution coefficient for Nb was found to be ≈0.5. The solidification sequence of INCONEL 718 was found to be (1) proeutectic γ, followed by (2) a γ/NbC eutectic at ≈1250°C, followed by (3) continued γ solidification, followed by (4) a γ/Laves phase eutectic at ≈1200°C. An estimate of the volume fraction eutectic is made using the Scheil solidification model, and the fraction of each phase in the eutectic is calculatedvia the lever rule. These are compared with experimentally determined values and found to be in good agreement.

The effects of heat treatment on the chromium depletion, precipitate evolution, and corrosion resistance of INCONEL alloy 690

Abstract: A series of heat treatments were performed to study the sensitization and the stress corrosion cracking (SCC) behavior of INCONEL Alloy 690. The microstructural evaluation and the chromium depletion near grain boundaries were carefully studied using analytical electron microscopy (AEM). The measured chromium depletion profiles were matched well to the calculated results from a thermodynamic/kinetic model. The constant extension rate test (CERT) was performed in the solution containing 0.001 M sodium thiosulfate (Na2S2O3) to study the SCC resistance of this alloy. The Huey test was also performed in a boiling 65 pct HNO3 solution for 48 hours to study the intergranular attack (IGA) resistance of this alloy. Both tests showed that INCONEL 690 has very good corrosion resistance. It is believed that the superior IGA and SCC resistances of this alloy are due to the high chromium concentration (≈30 wt pct). It is concluded in this study that INCONEL 690 may be a better alloy than INCONEL 600 for use as the steam generator (S/G) tubing material for pressurized water reactors (PWR's)

Welding of Inconel Alloy 718: A Historical Overview

Abstract: The introduction of Inconel alloy 718 represented a major advancement in the nickel-basesuperalloy class of materials. One of the most significant reasons was its lack of sensitivity to strain-age cracking during heat treatment of weldments. In addition, the general weldability of the alloy proved to be quite good. It has reasonably good resistance to fusion-zone cracking, and its sensitivity to heat-affected-zone microfissures in the base metal is comparable to other nickelchromium/nickel-chromium-iron alloys. The metallurgy of alloy 718 as it applies to welding issues, strain-age cracking behavior, and fusion-zone and heat-affected-zone fissuring resistance are reviewed in this paper. Superalloy 718-Metallurgy and Applications Edited by E.A. Loria The Minerals, Metals & Materials Society, 1989

The effects of heat treatment on the sensitization and SCC behavior of INCONEL 600 alloy

Abstract: A series of heat treatments were performed to study the sensitization effect on the stress corrosion cracking (SCC) behavior of INCONEL 600 alloy. The microstructural evolution and the chromium depletion near the grain boundary were carefully studied using analytical electron microscopy (AEM). Comparable constant load tests in the solution containing various concentrations of sodium thiosulfate (Na2S2O3) were, also performed in order to characterize the critical chromium concentration under the test conditions. It is observed that thermal treatment has a great effect on the microstructure and the chromium depletion profile of this alloy. Most specimens contained precipitates which were formed along grain boundaries in the semicontinuous form and were identified as M7C3 with a hexagonal crystal structure (a0=1.398 nm,C0=0.45 nm). Some intragranular precipitates which were identified as M23C6 with an fec crystal structure (a0=1.06 nm) were observed in the specimens aged for a longer period of time. The results of the constant load test showed that the susceptibility to SCC is sensitive to the chromium concentration at the grain boundary, and the minimum value to prevent SCC failure, under the test conditions, is approximately 8 wt pct.

The interaction of reaction-bonded silicon carbide and inconel 600 with a nickel-based brazing alloy

Abstract: The objective of the present research was to join reaction-bonded silicon carbide (RBSC) to INCONEL 600 (a nickel-based superalloy) for use in advanced heat engine applications using either direct brazing or composite interlayer joining. Direct brazing experiments employed American Welding Society (AWS) BNi-5, a commercial nickel-based brazing alloy, as a filler material; composite interlayers consisted of intimate mixtures of α-SiC and BNi-5 powders. Both methods resulted in the liquid filler metal forming a Ni-Si liquid with the free Si in the RBSC, which, in turn, reacted vigorously with the SiC component of the RBSC to form low melting point constituents in both starting materials and Cr carbides at the metal-ceramic interface. Using solution thermodynamics, it was shown that a Ni-Si liquid of greater than 60 at. pct Ni will decompose a-SiC at the experimental brazing temperature of 1200 ‡C; these calculations are consistent with the experimentally observed composition profiles and reaction morphology within the ceramic. It was concluded that the joining of RBSC to INCONEL 600 using a nickel-based brazing alloy is not feasible due to the inevitability of the filler metal reacting with the ceramic, degrading the high-temperature properties of the base materials.

Effect of thermomechanical treatments on short-range ordering and secondary-phase precipitation in NiCr-based alloys

Abstract: Effects of thermomechanical treatments on short-range ordering and secondary-phase precipitation have been studied in three NiCr based superalloys: (i) TD NiCr, an oxide dispersion strengthened and very low carbon alloy; (ii) Nimonic 75, a carbide and solid-solution strengthened alloy; (iii) Inconel X-750, a γ-strengthened, low carbon alloy. The different experimental techniques adopted, i.e. electrical resistivity, hardness and calorimetric measurements, showed varying sensitivity to ordering, precipitation and recrystallization phenomena. Hardness is particularly sensitive to effects of cold work, hard secondary-phase precipitation and recrystallization, whereas resistivity and specific heat are strongly affected by ordering and γ precipitation. The order-disorder transformation was the dominating microstructural feature in the metallurgical simple alloy TD NiCr, whereas in Nimonic 75 this transformation occurs along with carbide precipitation. In Inconel X-750 the precipitation of the γ′ phase sometimes overlaps and masks ordering effects. Cold working always causes a reduction in resistivity by disordering the material and provides lattice defects which enhance ordering during subsequent annealing.

The Role of Niobium and Other Refractory Elements in Superalloys

Abstract: This paper presents the results from ongoing research programs which study the effectiveness of niobium and tantalum in various nickel-base superalloys and ironnickel-base superalloy INCONEL 718,. This work not only shows the significance of niobium and tantalum as alloying additions in current superalloys, but also the necessity of these additions in the design of future superalloys demanding greater strength and temperature resistance.

The effect of alloy chemistry on creep behaviour in a helium environment with low oxygen partial pressure

Abstract: The alloy NiCr22W12Fe (Thermon 4972) has mechanical and creep rupture properties similar to those of the alloy NiCr22Co12Mo (Inconel 617) when air tested. In atmospheres with low oxygen partial pressure, such as helium with reactive components, the high-temperature corrosion resistance of Thermon 4972 was improved over Inconel 617 due to the formation of a protective oxide layer consisting of a manganese chromium spinel, which preserved the strength. For Inconel 617 the oxide layers are not protective. Strong internal oxidation and decarburization occurred, leading to a weakening of the material with increasing creep rupture time.

Sensitization of inconel 600. I. Scanning auger and optical microscopy

Abstract: The effect of impurity elements such as carbon, phosphorus, boron and silicon on the microstructural characteristics and grain-boundary chemistry of Inconel 600 has been investigated using optical microscopy and scanning Auger electron microscopy techniques. Of the elements added, only phosphorus was detected at grain boundaries and at the carbide-matrix interface. Carbon and boron were found to form discrete precipitates while silicon did not affect significantly the microstructural characteristics of the material. Sulphur-rich particles were found at the fractured surfaces and were associated with chromium carbides and titanium nitrides.

An analysis of specimen geometry effect on the creep life of inconel alloy X-750

Abstract: The effects of section size and specimen geometry (flat, tubular and solid specimens) on the creep behaviour of a nickel-base superalloy (Inconel X-750) have been elicited. The effect of the section size was observed in all three specimen geometries; time to fracture was progressively shortened as the specimen thickness was reduced. The creep behaviour exhibited by the alloy in the three specimen geometries was compared on the basis of similar section size. It emerged that the times to rupture of tubular specimens were considerably longer than those of flat and solid specimens while the minimum creep rate at all the applied stresses was found to be nearly unaffected by the specimen geometry. It is shown that the principle of the volume to surface ratio is applicable and the equivalence of creep life data in different geometries is obtained when a comparison is made using the ratio of the cross-sectional area to the perimeter as the normalizing parameter.

Sensitization of inconel 600. II. Analytical electron microscopy

Abstract: Analytical electron microscopy has been used to study the effect of trace impurity elements, such as carbon, phosphorus, boron and silicon, on the microstructural characteristics of Inconel 600. Sulphide particles, rich in manganese and chromium, have been detected in association with both titanium nitride and chromium carbide, and the structure, lattice parameters and crystallographic orientation relationship between the γ-M23C6 and sulphide determined. Additions of carbon to the base alloy caused extensive precipitation of carbides, mainly of the M7C3 type. In the annealed alloy, these carbides were found to outline prior austenite grain boundaries and, on subsequent ageing, precipitated at the existing boundaries. Trace additions of boron to the base alloy increased the twin frequency by enhancing precipitation at non-coherent twin boundaries. These new precipitates were rich in chromium but also contained some iron and nickel. Additions of silicon did not alter the microstructure of the base ...

The development of the deformed microstructure in commercially pure nickel

Abstract: The development of the deformed microstructure in Inconel 200 (commercial-purity nickel) is described. Experiments were undertaken in uniaxial tension to strains of 0.25 at strain rates from 10 −5 s −1 to 5×10 −3 s −1 over a range of temperatures from 300 to 800 K. The effects of these variables on the developing microstructure are described and particular attention is paid to the conditions for cell and subgrain formation and to the formation of microbands. Microbands were seen in Inconel 200 following tensile deformation to a strain of 0.25 at a strain rate of 5 × 10 −3 s −1 and the number of grains containing microbands increased with increasing deformation temperature over the temperature range studied.

Interaction of ceramic cutting tools with nickel-based alloys

Abstract: In order to identify the chemical wear mechanisms affecting the lifetime of ceramic cutting tools, the interactions of ceramic-nickel-based alloys were studied via diffusion tests. Three ceramics and two superalloys were tested: SiAlON, zirconia-toughened alumina and alumina-SiC whiskers composite against Inconel 718 and Waspaloy. Diffusion tests were conducted in vacuum at 1200 °C; transverse sections of different diffusion couples were examined. The characterization of the reaction was conducted using scanning electron microscopy, electron microprobe and X-ray analysis. The formation of molten silicides at the interface and the enrichment of the diffusion zone with chromium, niobium and molybdenum were outlined; carbides and nitrides are also likely to form.

Pitting and stress corrosion cracking behaviour of INCONEL 600 alloy in thiosulphate solution

Abstract: The effect of thiosulphate ions on the pitting corrosion and stress corrosion cracking behaviour of solution-treated INCONEL 600 alloy was investigated. In the absence of chloride ions, pitting corrosion was observed on the specimen surfaces of solution-treated INCONEL 600 alloy, in thiosulphate solution. Intergranular stress corrosion cracking in this material was also found to occur in thiosulphate solution at 95 °C and at applied potentials of −440 and +100 mV (SCE). Crack growth rates as a function of stress intensity (da/dt vs. K) at these two potentials are reported. The possible mechanism for these observations is discussed.

The oxidation performance of Cr2 O3-forming commercial iron-nickel alloys at high temperature

Abstract: The oxidation of commercial iron-nickel-base and nickel-base Cr203-forming alloys in oxygen under isothermal conditions at 800°C and lOOO°C has been investigated. Although the scales developed on Incoloy DS, Incoloy 800H, Incoloy 825 and Inconel 625 are reasonably protective, those on the first three alloys are partlcularly susceptl~le to failure on cooling. Intergranular oxidation is substantial and can be correlated wlth. the depth of chromium depletion in the subjacent alloy. Void formation at the alloy grau,,: boundaries is particularly severe for Incoloy DS. The roles of the varwus. minor alloymg additions manganese, titanium, silicon, aluminium, molybdenum and mobwm. are. considered and correlated with the overall oxidation process. Manganese and titanium can diffuse relatively rapidly across the scale to form new oxide on the scale. surface, while aluminium and silicon form internal oxides only. Molybdenum and niobium have little effect on the overall behaviour of Incoloy 825 and Inconel 62...

Creep behaviour of the intermetallic B2 phase (Ni,Fe)Al with strengthening soft precipitates

Abstract: The creep behaviour of Fe-Ni-Al alloys with the intermetallic (Ni,Fe)Al phase (B2 structure) as matrix and /alpha/-Fe precipitate particles (disordered bcc structure) is studied at 900 and 1000/sup 0/C and compared with that of single-phase B2-(Ni,Fe)Al and other two-phase Fe-Ni-Al alloys with the (Ni,Fe)Al phase. The observed creep behaviour is controlled primarily by dislocation creep which is described by the conventional power law (Dorn equation) with a threshold stress for the strengthening precipitates. Deformation mechanism maps have been calculated. The creep resistance of the investigated alloys is of the order of that of the nickel-base superalloy Inconel 617. (orig.).

Fatigue Crack Growth Properties of Ni-Base Alloys in High Pressure Hydrogen at Room Temperature

Abstract: The fatigue crack growth properties of the Inconel 718 and Udimet 720 Ni-base alloys being used for liquid hydrogen fueled rocket engine materials were investigated as functions of ΔK and frequency in a high pressure hydrogen of 19.7MPa at room temperature. The results obtained are as follows;(1) The fatigue crack growth rate in hydrogen was larger than that in argon for both Inconel 718 and Udimet 720. The effect of hydrogen on fatigue crack growth rate increased with decreasing the frequency of the cyclic loading. The effect of hydrogen on fatigue crack growth of Udimet 720 was higher than that of Inconel 718.(2) Above the ΔK which the striations were observed on the fracture surface in argon, hydrogen showed marked effect on the fatigue crack growth, i.e., the fracture along the interfaces between δ phase and γ matrix for Inconel 718 and that the interfaces between γ' phase and γ matrix for Udimet 720 were observed on the fracture surface in hydrogen, respectively.

High Temperature Corrosion Analysis of Inconel 617 | Thermal Energy Storage Capsules

Abstract: The corrosion degradation of three Inconel 617 Alloy Thermal Energy Storage capsules filled with eutectic fluoride salts LiF-MgF2-KF, LiF-MgF2-NaF and LiF-MgF2 were analyzed. The ultrahigh purity fluoride salts were previously sealed inside the Inconel capsules under controlled processing conditions and thermally cycled in vacuum over a temperature differential of 200 K near 1000 K for 10,000 hr. It was determined that the microstructural degradation is minimal but some aluminum from the alloy may have been displaced into the salt. Comparisons are made with previously reported equilibrium calculations and a semiquantitative diffusion model is presented to support the possibility of diffusion control over the corrosion. The results indicate that Inconel 617 may be a suitable material for fluoride salts in thermal energy storage applications.

High performance alloy electroforming

Abstract: Electroformed copper and nickel are used in structural applications for advanced propellant combustion chambers. An improved process has been developed by Bell Aerospace Textron, Inc. wherein electroformed nickel-manganese alloy has demonstrated superior mechanical and thermal stability when compared to previously reported deposits from known nickel plating processes. Solution chemistry and parametric operating procedures are now established and material property data is established for deposition of thick, large complex shapes such as the Space Shuttle Main Engine. The critical operating variables are those governing the ratio of codeposited nickel and manganese. The deposition uniformity which in turn affects the manganese concentration distribution is affected by solution resistance and geometric effects as well as solution agitation. The manganese concentration in the deposit must be between 2000 and 3000 ppm for optimum physical properties to be realized. The study also includes data regarding deposition procedures for achieving excellent bond strength at an interface with copper, nickel-manganese or INCONEL 718. Applications for this electroformed material include fabrication of complex or re-entry shapes which would be difficult or impossible to form from high strength alloys such as INCONEL 718.

Effect of Chemistry and Processing on the Structure and Mechanical Properties of Inconel Alloy 718

Abstract: Alloy 718 has been utilized in gas turbine engines for almost 30 years because of its extremely good mechanical properties.\"30ver the years the property levels attained with the alloy have been increased by altering the thermomechanical history as discussed by LoriaP The chemical composition range for the alloy has remained relatively stable over the years, although there has been a tightening of the columbium range along with tighter control of minor elements such as magnesium and sulfur. Recently there has been interest in the stabilizing of Y\" by adjustments of aluminum, titanium, and columbium. Superalloy 71 &Metallurgy and Applications Edited by E.A. Loria The Minerals, Metals & Materials Society, 1989

Stresses associated with Inconel 600 oxidation

Abstract: The aim of this study was to analyze the influence of a previous deformation or of presulphidation of an Inconel 600 alloy (synthetic and industrial grade) on stress evolution in the oxide scale. The experiments were performed mainly by deflection of a thin foil, and the stresses were analyzed using the models of Norin, Morton and Brenner. First, the influence of the dissolved oxygen and of the protective layer of SiO 2 were analyzed. Then, during the growth of the oxide layers, two distinct mechanisms were discussed for the relaxation of the stresses by the diffusion creep (Gangulee's model) or the deformation by curvature of the thin foil. The prevention of the relaxation of the stresses by diffusion creep is primarily associated with the formation of minor oxides (or carbides) in the pores of the inner Cr 2 O 3 layer. On the other hand, sulphur-diffusing into the oxide because of sulphide decomposition in the alloy increases the chromium vacancy content, due to sulphide ions (S − ) on chromium sites of Cr 2 O 3 . This helps the diffusion creep relaxation. Previous deformation of the substrate induces a relaxation mechanism mainly by creep of the substrate.

A Mechanism for Hydrogen Induced IGSCC in Inconel 600

Abstract: Intergranular stress corrosion cracking (IGSCC) of INCONEL 600 in high temperature deaerated water has been termed ‘hydrogen induced IGSCC. It is suggested here that these cracks are initiated by the nucleation of a high density of methane bubbles on the grain boundaries under the combined action of the applied stress, and high pressure methane formed from carbon in solution reacting with hydrogen injected by corrosion. The bubbles then grow together to give local failure by grain boundary diffusion. The thermodynamics and kinetics of this process are examined and shown to be in quantitative agreement with several experimental observations. The mechanism involves no dissolution of the metal, the role of corrosion being the injection of hydrogen at a high fugacity.

Thermal conductivity of Inconel 600 and Ti-6Al-4V from 360 K to 900 K

Abstract: Mesures de la conductivite thermique a l'aide d'un appareil a ecoulement de chaleur axial relatif controle par ordinateur. On observe une augmentation de la conductivite thermique avec la temperature et on montre qu'elle peut etre decrite par des equations lineaires

Hydrogen Assisted Fracture of Inconel 600 Charged at High Temperature

Abstract: Effect of hydrogen charging from the gas phase at 350–600°C and 30–45 MPa as well as subsequent ageing at room tenperature on fracture mode and plasticity of Inconel 600 has been studied. No change in microstructure has been produced by charging below 550 and 40 MPa whereas exposure at higher temperature and pressure caused hydrogen attack. Ageing at RT changed the distribution of hydrogen in metal and thus modified the fracture mode and plasticity. Hydrogen present in solid solution decreased plasticity much more than that segregated around inclusions.

Effect of pulse duty cycle on Inconel 718 laser welds

Abstract: Crack sensitive Inconel 718 was laser pulse welded using a 3.0 kW CO2 laser. Weld shape, structure, and porosity were recorded as a function of the pulse duty cycle. Within the matrix studied, the welds were found to be optimized at a high (17 ms on, 7 ms off) duty cycle. These welds were superior in appearance and lack of porosity to both low duty cycle and CW welds.

An Analysis of the Effect of Environmental Damage on the Creep Fracture of Inconel Alloy X–750

Abstract: A mathematical model which allows for the analysis of the effect of environmental damage, caused by prior exposure of test samples to high temperature oxygen environment, on the creep life and ductility has been developed. This model developed specifically for nickel-base superalloys considers two forms of environmental damage one characterized by a profusely cavitated region and the other a free region of poor creep strength. The predictions of this model are discussed in detail and also compared with the experimental results of Pandey, Taplin, Ashby and Dyson (1986) on Inconel X-750 alloy.