Showing papers on "Inconel published in 2000"

Microstructural features of dissimilar welds between 316LN austenitic stainless steel and alloy 800

Abstract: For joining type 316LN austenitic stainless steel to modified 9Cr–1Mo steel for power plant application, a trimetallic configuration using an insert piece (such as alloy 800) of intermediate thermal coefficient of expansion (CTE) has been sometimes suggested for bridging the wide gap in CTE between the two steels. Two joints are thus involved and this paper is concerned with the weld between 316LN and alloy 800. These welds were produced using three types of filler materials: austenitic stainless steels corresponding to 316, 16Cr–8Ni–2Mo, and the nickel-base Inconel 182 1 . The weld fusion zones and the interfaces with the base materials were characterised in detail using light and transmission electron microscopy. The 316 and Inconel 182 weld metals solidified dendritically, while the 16–8–2 (16%Cr–8%Ni–2%Mo) weld metal showed a predominantly cellular substructure. The Inconel weld metal contained a large number of inclusions when deposited from flux-coated electrodes, but was relatively inclusion-free under inert gas-shielded welding. Long-term elevated-temperature aging of the weld metals resulted in embrittling sigma phase precipitation in the austenitic stainless steel weld metals, but the nickel-base welds showed no visible precipitation, demonstrating their superior metallurgical stability for high-temperature service.

Fatigue strength of Inconel 718 at elevated temperatures

Abstract: The strength of Inconel 718 under rotary bending fatigue is investigated at room temperature, 300, 500 and 600 °C in air. It is found that in the long-life region, the fatigue strength of a plain specimen is much higher at elevated temperatures than at room temperature, though the static strength decreases with the increase in temperature. The effect of temperature on the fatigue strength is examined in terms of the initiation and early growth behaviour of a small crack. The results are discussed in relation to the competition between the softening of the nickel matrix (γ phase) and the surface oxidation at elevated temperatures.

The microstructure of continuously processed Yba2Cu3Oy coated conductors with underlying CeO2 and ion-beam-assisted yttria-stabilized zirconia buffer layers

Abstract: The microstructural development of YBa2Cu3Oy (Y-123) coated conductors based on the ion-beam-assisted deposition (IBAD) of yttria-stabilized zirconia (YSZ) to produce a biaxially textured template is presented. The architecture of the conductors was Y-123/CeO2/IBAD YSZ/Inconel 625. A continuous and passivating Cr2O3 layer forms between the YSZ layer and the Inconel substrate. CeO2 and Y-123 are closely lattice-matched, and misfit strain is accommodated at the YSZ/CeO2 interface. Localized reactions between the Y-123 film and the CeO2 buffer layer result in the formation of BaCeO3, YCuO2, and CuO. The positive volume change that occurs from the interfacial reaction may act as a kinetic barrier that limits the extent of the reaction. Excess copper and yttrium generated by the interfacial reaction appear to diffuse along grain boundaries and intercalate into Y-123 grains as single layers of the Y-247, Y-248, or Y-224 phases. The interfacial reactions do not preclude the attainment of high critical currents (Ic) and current densities (Jc) in these films nor do they affect to any appreciable extent the nucleation and alignment of the Y-123 film.

Microstructural evolution of Inconel* 718 during ingot breakdown: process modelling and validation

Abstract: A computer model is presented that describes microstructural evolution during the ingot breakdown of nickel base superalloy Inconel 718 via the open die cogging operation. To support the development of the model, a compression testing programme has been carried out which covers the ranges of temperatures, strains, and strain rates experienced during thermomechanical processing. Analysis of the flow curves has allowed the identification of the regimes in which the various deformation mechanisms take place. Logic based rules have been incorporated into the model, and this has allowed predictions of the microstructural evolution to be made. Where possible, the results have been compared with the available experimental data and it is shown that theory and experiment are in reasonable agreement. A number of computational experiments have been carried out, to study the effects of changing the forging procedure.

SEM-EDS and XPS Studies of the High Temperature Oxidation Behaviour of Inconel 718

Abstract: The oxidation in air under isothermal conditions of Inconel 718 has been investigated at 900 °C. We have studied the firsts stages of the high temperature oxidation mechanism. The oxidised samples were examined using a number of surface analytical techniques including XPS and SEM-EDS. The results have shown that minor alloying elements strongly influence the oxidation behaviour of the alloy:

Wear of Coated Carbide Tools When Machining Nickel (Inconel 718) and Titanium Base (Ti-6A1-4V) Alloys

Abstract: Nickel base, Inconel 718, and titanium base, IMI 318 (Ti-6A1-4V) alloys were machined with single (TiN) and multiple (TiN/TiCN/TiN) PVD coated carbide inserts at high cutting conditions in order to evaluate their performance and also to analyze their failure modes. The machining results show that coating material(s), tool geometry, machining parameters as well as material properties can singly or jointly affect tool performance and failure modes. Flank wear was the dominant failure mode at cutting speeds up to 42 m/min for the Inconel 718 alloy and up to 100 m/min for the IMI 318 alloy when machining at feed rates up to 0.25 mm/rev and depth of cut up to 2.00 mm. Excessive chipping/flaking off of tool particles and premature edge fracture also contributed to tool rejection, particularly when machining with the multi-coated inserts due to their sharp edges and instability of the machining system at higher speed conditions. The multi-layer coated tools generally produced lower flank wear rates, thus the bes...

Characterization of Carbon Deposits from Jet Fuel on Inconel 600 and Inconel X Surfaces

Abstract: Flow reactor experiments were conducted to study carbon deposit formation from decomposition of a jet fuel (JP-8) at 500 °C and 500 psig for 5 h on the surface of two superalloys, Inconel 600 and Inconel X. The deposits collected on superalloy surfaces were characterized by temperature-programmed oxidation, size exclusion microscopy, and energy-dispersive X-ray spectroscopy. Significantly lower deposition on Inconel X compared to that on Inconel 600 was attributed to the presence of minor elemental components, such as Al, Ti, Nb, and Ta in the Inconel X alloy.

Simultaneous Optimization of Machining Parameters for Dimensional Instability Control in Aero Gas Turbine Components Made of Inconel 718 Alloy

Abstract: Aero gas turbine components made of Inconel 718 superalloy revealed significant dimensional instability after machining. The dimensional instability is a manifestation of alterations in residual stresses and microstructure, which are influenced by machining parameters. This paper presents a simultaneous optimization technique used to control the dimensional instability in turning operation. Empirical equations are established for predicting surface residual stresses, surface finish, dimensional instability and tool life using response surface methodology. Experimental results show a strong correlation between residual stresses and dimensional instability. A desirability function approach is used to optimize the multiple responses and machining parameters are derived for practical applications. Inconel 718 test specimen and jet engine components machined with optimal cutting parameters show dimensional instability within the acceptable tolerance band.

Brazing of Inconel X-750 to stainless steel 304 using induction process

Abstract: The proposed paper discusses results of the joining of Inconel X-750 to stainless steel 304 by induction brazing. The experimental brazing was carried out at 1423 K using a nickel-based brazing BNi-2 (Ni–7Cr–3Fe–3.2B–4.5Si–0.06C wt.%) filler metal. By means of induction heating, joining process can be completed within seconds in argon ambient. The effects of joining time on the microstructures of joint and base materials, elemental distribution within the brazed joint, and the joint shear strengths were investigated. Experimental results show that BNi-2 containing boron and silicon melting point depressants can achieve good wetting and spreading between Inconel X-750 and stainless steel 304. Joint shear strengths of as high as 483 MPa were obtained when processed at approximately 1423 K for 180 s. The width of the braze-affected zone increases with increasing joining time but it does not cause any significant reduction in the joint strength. Inconel X-750 and stainless steel 304 exhibited no noticeable change in their microstructures due to the rapid heating cycle of induction processing.

High temperature fatigue crack growth in Inconel 718

Abstract: The nickel base superalloys are extensively used in high temperature applications, so it is important to know their behaviour under conditions of high-temperature fatigue. This paper studies the influence of ΔK, loading frequency, stress ratio and temperature on the high temperature fatigue crack growth rate of nickel base superalloys. This study is based on fatigue tests carried out in corner crack specimens of Inconel 718 at 600°C and at room temperature. Three stress ratios (R = 0.05, 0.5 and 0.8) and loading frequencies ranging from 0.0017 to 15 Hz were considered in the tests. For frequencies below 0.25 Hz, the load wave shape was trapezoidal with different dwell times at maximum load. At relatively high frequencies the propagation is cycle dependent, while for lower frequencies it is time dependent. At intermediate frequencies a mixed crack growth occurs. The transition frequencies from cycle dependent to mixed regime and from mixed to time dependent regime were obtained for each R. The incr...

Wear Behavior of PVD and CVD Coated Carbide Tools when Face Milling Inconel 718

Abstract: The wear behavior of two types of coated cemented carbide tools has been studied when face milling a nickel-based superalloy Inconel 718. PVD-TiN and CVD-TiCN+Al2O3 tools were used. It was found that the coatings were detached after only five seconds of cutting. An attrition type wear mechanism associated with workpiece material adhesion was observed which eventually led to severe chipping, flaking, plastic deformation and cracking. It was noted that the coatings had no significant effect on tool performance under the cutting conditions tested. Presented at the 54th Annual Meeting Las Vegas, Nevada May 23–27, 1999

Dimensional instability studies in machining of Inconel 718 nickel based superalloy as applied to aerogas turbine components

Abstract: Inconel 718 alloy is used extensively in aerogas turbines and this alloy is most difficult to machine and highly prone to dimensional instability after machining. Such detrimental phenomenon poses an enormous problem in engine assembly and affects structural integrity. This paper highlights the systematic research work undertaken to study the plastic deformation characteristics of Inconel 718, and the effect of process variables on machined surface, subsurface, and dimensional instability. Also illustrated is the technique developed for simultaneous optimization of several process variables such as cutting speed, feed, depth of cut, rake angle, and tool nose radius to control the residual stresses and dimensional instability within the acceptable tolerance band of the component. Prediction equations were developed for residual stress, dimensional instability, tool life, surface finish, and material removal rate. Predicted data were validated experimentally. This paper also presents the qualitative and quantitative data on dimensional instability with specific case studies of jet engine components, and it clearly illustrates the approach followed to develop a technique to control such detrimental effect.

Electro-spark deposition coatings for high temperature oxidation resistance

Abstract: A simple but efficient technique has been developed to produce surface coatings on metals and alloys. This technique uses direct high frequency electrical sparks to melt and deposit metal or alloy coatings onto substrate surface. The present paper reports Al and FeCrAl coatings on AISI 304, 310 and 430 stainless steel and Inconel 600 substrates. Isothennal oxidation in air indicated that the oxidation rates of the coated specimens were much lower than that of the un-coated specimens. The scale spallation resistance was also dramatically improved. The phases and microstructures of the coatings and oxide scales were characterised using XRD and HRSEM. The properties of the different coatings were compared; and the effects of the processing parameters were discussed based on the experimental results. Further improvements in an effort to obtain thicker and more uniform coatings with better oxidation resistance and to use this technique in industrial applications were also proposed.

The non-destructive estimation of the superficial mechanical properties of components in the INCONEL 600 alloy by X-ray diffraction peak width

Abstract: INCONEL 600 alloy is largely used as nuclear power center components. The non-destructive determination of the superficial mechanical proprieties is indispensable for the qualification of the fabrication process and for the service duration estimation in aggressive environment. X-ray diffraction (XRD) technique is non-destructive and can be used to determine microscopic internal stresses from the broadening of the XRD peaks. The average magnitude of XRD peak broadening is related directly to the hardness, the elastic limit or degree of cold work of the material which can be used as a means of quantifying the surface mechanical properties. With an empirical relationship between the {311} XRD peak width and the conventional mechanical proprieties (hardness, elastic limit, hard work degree) for INCONEL 600 alloy, the superficial mechanical characteristics can be estimated from diffraction peak width for just finished parts or for maintenance pieces. Several TEM observations are also realized for microstructure study.

Effect of sulphur on hot ductility and heat affected zone microfissuring in Inconel 718 welds

Abstract: The influence of sulphur on microfissuring has been studied by characterising the hot ductility and heat affected zone (HAZ) microfissuring in welded wrought Inconel 718. A series of Inconel 718 base alloys, with sulphur concentrations in the range 7–110 wt-ppm and with the lowest possible concentrations of carbon, boron, and phosphorus were used in the study. The hot ductility of the alloys was measured using a Gleeble 1500 system, and their weldability was evaluated by bead on plate electron beam welding. The effect of sulphur on microfissuring in the weld HAZ was compared with that of boron in boron containing, but sulphur free, alloys. Sulphur reduced the weldability of the material, but its influence was very moderate in comparison with that of boron. The rate of increase of the brittle temperature range hot ductility parameter with increasing sulphur concentration was significantly smaller compared with that with increasing boron concentration. This may be because sulphur and boron seem to i...

Effect of grain size on heat affected zone cracking susceptibility.Study of weldability of Inconel 718 cast alloy (2nd Report)

Abstract: Introduction A previous report has shown that Inconel 718 cast alloy faces the problem of liquation cracking in the heat affected zone (HAZ) and clarifies that HAZ cracking is mainly due to grain boundary liquation associated with constitutional liquation of the Laves cluster. These results suggest that, to improve the HAZ cracking susceptibility, it is basically necessary to find a way of reducing the grain boundary liquation caused by constitutional liquation of the Laves cluster. For this purpose, it is effective to reduce the amount of Laves cluster present at the grain boundaries in the base metal. The extent to which the Laves cluster is formed at the grain boundaries varies depending on the alloy chemistry, granular structure, heat treatment, etc. To improve HAZ cracking in Inconel 718 cast alloy, it is necessary to clarify the effects of these factors on the HAZ cracking susceptibility. Previous research intended to establish the relationship between the HAZ cracking susceptibility and grain size among these factors has been mainly focused on the forged alloy. That is to say, Thompson et al, Lucas et al and Robinson et al have shown that the HAZ cracking susceptibility of Inconel 718 forged alloy can be improved by grain refinement. However, relatively few quantitative research efforts have so far been mounted to determine the relationship between the HAZ cracking susceptibility and grain size of Inconel 718 cast alloy, and many obscure aspects concerning the mechanism of HAZ cracking susceptibility improvement remain to be clarified. To obtain fundamental data relating to improvement of HAZ cracking, Inconel 718 cast alloy specimens with different grain sizes are subjected to the spot varestraint test and the isothermal liquation test, and the effect of the grain size on the HAZ cracking susceptibility is investigated. Based on these results, the mechanism of HAZ

Superplastic behaviour of Inconel* 718 sheet

Abstract: Inconel 718 is a nickel based alloy used extensively in the aerospace industry, having good service capabilities, in terms of strength and fatigue resistance, at high temperatures. Inconel 718, in the form of sheet, has the capability of being shaped using gas pressure forming techniques similar to those used for a number of aluminium and titanium based alloys. An extensive research programme has been carried out to investigate the high temperature formability of this alloy. This has involved both uniaxial tensile testing to determine such parameters as flow stress and strain rate sensitivity, and microstructural examination to investigate grain stability under both static heating and following deformation. The forming characteristics of the material have been correlated with the δ phase solvus temperature determined using SEM techniques. Optimum forming temperatures and strain rates are discussed.

Diffusion bonding of a superplastic Inconel 718SPF superalloy by electroless nickel plating

Abstract: Although intimate contact can be obtained for diffusion bonding of a superplastic Inconel 718SPF superalloy under a low pressure of 7 MPa, the precipitates formed at the interface retarded achievement of a sound joint. The shear strength was only 41.5 MPa for an overlap length of 12 T (T=1.3 mm, sheet thickness). The diffusion bondability of this Inconel 718SPF superalloy was enhanced by electroless nickel plating. In this situation, the bonding shear strength increased to 70.4 MPa for the same overlap length of 12 T under the same bonding condition, regardless of the roughness of the surface to be bonded. Upon decreasing the overlap length from 12 to 6 T, the bonding strength remained constant.

Long Term Thermal Stability on INCONEL Alloys 718, 706, 909, and Waspaloy at 593C and 704C

Abstract: This paper presents a study of the isothermal stability of INCONEL” alloys 718, 706, 909, and WASPALOY**. Standard annealed and aged materials were exposed at 593’C up to 10,OOOh and at 704’C up to 5,000h. The exposed materials were tested for room temperature tensile, room temperature impact, and high temperature tensile. The strength of alloy 909 degraded on 593°C exposure but 706 and 718 retained their strength. At 704°C exposure, WASPALOY had the best stability in terms of high temperature strength whilst 909 was the poorest and retained only 50% of its strength. On 704°C exposure, alloy 706 and WASPALOY retained their room temperature impact strength better than ahoy 718. The tested materials were subjected to optical microscopy to develop an understanding of the reasons for the above results. * INCONEL is a trademark of the Special Metals Family of Companies ** WASPALOY is a trademark of the United Technology Corporation Superalloys 2ooo Edited byT.M. Pollock, R.D. Kissinger. R.R. Bowman, K.A. Green, M. McLean. S. Olson, and J.J. Schirm TMS CThe Minerds, Metals &Materials Society), 2ooO

A Study on Fusion Repair Process for a Precipitation Hardened IN738 Ni-Based Superalloy

Abstract: Several fusion repair processes such as laser cladding, laser welding and gas tungsten arc welding have been taken into consideration for repairing IN738 precipitation hardened Ni-based superalloy material. Effect of heat input on weld cracking susceptibility has been studied to obtain optimum condition for crack-free welds. Variations in cracking susceptibility as a function of welding heat input is discussed with reference to metallurgical characteristics of the welds.

Welding method for different material

Abstract: PROBLEM TO BE SOLVED: To provide a welding method for different material in which cracks do not penetrate in a welding joint of different materials of an austenitic stainless steel pipe with a CrMo steel pipe even after using for a long time. SOLUTION: In this welding method for different material, an austenitic stainless steel pipe 1 is welded to a low alloy steel 2 with an Inconel series welding material, and a cladding by welding metal 4 is formed or a weld metal having a final layer by overlaying is formed so as to differ a position of heat affected zone on the low alloy steel side from a position where Cr content on the outside surface is changed. COPYRIGHT: (C)2002,JPO

Characteristics of heat affected zone cracking in Inconel 718 cast alloy. Study of weldability of Inconel 718 cast alloy (1st Report)

Abstract: (2000). Characteristics of heat affected zone cracking in Inconel 718 cast alloy. Study of weldability of Inconel 718 cast alloy (1st Report) Welding International: Vol. 14, No. 5, pp. 365-374.