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Welding and Weldability of Thorium-Doped Iridium Alloys

Description: Ir-0.3%W alloys doped with thorium are currently used as post-impact containment material for radioactive fuel in thermoelectric generators that provide stable electrical power for a variety of outer planetary space exploration missions. Welding and weldability of a series of alloys was investigated using arc and laser welding processes. Some of these alloys are prone to severe hot-cracking during welding. Weldability of these alloys was characterized using Sigmajig weldability test. Hot-cracking is influenced to a great extent by the fusion zone microstructure and composition. Thorium content and welding atmosphere were found to be very critical. The weld cracking behavior in these alloys can be controlled by modifying the fusion zone microstructure. Fusion zone microstructure was found to be controlled by welding process, process parameters, and the weld pool shape.
Date: March 12, 2000
Creator: David, S.A.; Ohriner, E.K. & King, J.F.
Partner: UNT Libraries Government Documents Department


Description: This task supports the change from an oil mixture termed 50:50 oil (an equal parts mixture of Milpro 634 and Pennex N47) to a new oil mixture (Castrol Illocut 334). This change was necessitated by a KCP vendor no longer supplying the Pennex N47 component of the 50-50. In order to continue production of machined parts, a detailed process was followed to ensure that high quality parts could be manufactured and that the cutting oil selected would provide acceptable human performance characteristics, e.g., skin irritability, smell, etc. A prime consideration in changing the oil was that no apparent change in the pinch weldability of the fill stems fabricated using the new oil and process parameters, if any, be observed. A two part approach, as detailed in the plan shown in Appendix B, was used to qualify the effect of the process on pinch weld characteristics. In the first phase, ref. 1., the weld parameter window was defined using fill stems made from 304L, 21-6-9, and 316 stainless steel. These weld conditions were then subsequently used for the Castrol Illocut 334 machined fill stems. The results of this activity are reported in this document. A follow-on task of welding in the facility was requested by one of the design agencies and this will be completed and reported separately.
Date: February 28, 2008
Creator: Korinko, P & David Maxwell, D
Partner: UNT Libraries Government Documents Department

Weld Properties of a Free Machining Stainless Steel

Description: The all weld metal tensile properties from gas tungsten arc and electron beam welds in free machining austenitic stainless steels have been determined. Ten heats with sulfur contents from 0.04 to 0.4 wt.% and a wide range in Creq/Nieq ratios were studied. Tensile properties of welds with both processes were related to alloy composition and solidification microstructure. The yield and ultimate tensile strengths increased with increasing Creq/Nieq ratios and ferrite content, whereas the ductility measured by RA at fracture decreased with sulfur content. Nevertheless, a range in alloy compositions was identified that provided a good combination of both strength and ductility. The solidification cracking response for the same large range of compositions are discussed, and compositions identified that would be expected to provide good performance in welded applications.
Date: August 1, 2000
Creator: Brooks, J. A.; Goods, S. H. & Robino, C. V.
Partner: UNT Libraries Government Documents Department

Nickel based superalloy with improved weldability and oxidation resistance. Fifth quarterly report for the period November 1999 - January 2000

Description: This program is part of the US Department of Energy (DOE) Energy Related Inventions Program (ERIP). The purpose of ERIP is to promote and facilitate the development of energy saving technologies that may not otherwise be developed solely by commercial enterprises. The program has been highly successful in achieving its mission. The aim of this project is to determine and provide technical and economic data to a commercial end user of the alloy so that a full-scale alloy qualification program can be defined and implemented. The object of this project is to define the compositional range for a new alloy that is suitable for evaluation and qualification by a commercial enterprise. Alloy properties that will need to be determined include weldability, oxidation resistance, creep strength, resistance to thermo-mechanical fatigue, microstructure stability, and cost. Test results will be used to finalize the compositional range of an alloy that will undergo a rigorous qualification process.
Date: February 29, 2000
Creator: Simkovich, George & Whitney, Eric
Partner: UNT Libraries Government Documents Department

Nickel Based Superalloy with Improved Weldability and Oxidation Resistance. Fourth quarterly report for the period July 1999 to October 1999

Description: The aim of this project is to determine and provide technical and economic data to a commercial end user of the alloy so that a full-scale alloy qualification program can be defined and implemented. The object of this project is to define the compositional range for a new alloy that is suitable for evaluation and qualification by a commercial enterprise. Alloy properties that will need to be determined include weldability, oxidation resistance, creep strength, resistance to thermo-mechanical fatigue, microstructure stability, and cost. Test results will be used to finalize the compositional range of an alloy that will undergo a rigorous qualification process.
Date: November 1, 1999
Creator: Simkovich, George & Whitney, Eric
Partner: UNT Libraries Government Documents Department

Laser beam welding of AZ31B-H24 magnesium alloy.

Description: The laser beam weldability of AZ31B magnesium alloy was examined with high power CW CO{sub 2} and pulsed Nd:YAG lasers. The low viscosity and surface tension of the melt pool make magnesium more difficult to weld than steel. Welding parameters necessary to obtain good welds were determined for both CW CO{sub 2} and pulsed Nd:YAG lasers. The weldability of the magnesium alloy was significantly better with the Nd:YAG laser. The cause of this improvement was attributed to the higher absorption of the Nd:YAG beam. A lower threshold beam irradiance was required for welding, and a more stable weldpool was obtained.
Date: September 29, 1998
Creator: Leong, K. H.
Partner: UNT Libraries Government Documents Department

Weldability of Fe-Al-Cr Overlay Coatings for CorrosionProtection in Oxidizing/Sulfidizing Environments

Description: The effect of chromium additions to the weldability of Fe-Al based overlay claddings are currently being investigated for the corrosion protection of boiler tubes in Low NOx furnaces. The primary objective of this research is to identify weldable (crack-free) Fe-Al-Cr weld overlay coating compositions that provide corrosion resistance over long exposure times. During the current project phase, preliminary corrosion testing was conducted on several ternary Fe-Al-Cr alloys in two types of gaseous corrosion environments. These long-term corrosion tests were used to develop a target weld composition matrix and serve as a base line for future corrosion tests. Preliminary Fe-Al based welds with various aluminum concentrations and one ternary Fe-Al-Cr weld overlay were successfully deposited using a Gas Tungsten Arc Welding (GTAW) process and cracking susceptibility was evaluated on these coatings.
Date: March 4, 2003
Creator: Regina, JR
Partner: UNT Libraries Government Documents Department

Summary of beryllium specifications

Description: This report summarizes and compares the main beryllium properties included in producer, Department of Energy (formerly ERDA) facility, and government specifications. These data are tabulated in a sequence established primarily by increasing purity and secondarily by increasing tensile properties. Comments on formability and weldability are also included.
Date: February 17, 1978
Creator: Corle, R. R.
Partner: UNT Libraries Government Documents Department

Weld overlay cladding with iron aluminides

Description: The hot and cold cracking tendencies of some early iron aluminide alloy compositions limited their use to applications where good weldability was not required. Considerable progress has been made toward improving this situation. Using hot crack testing techniques developed at ORNL and a systematic study of alloy compositional effects, we have established a range of compositions within which hot cracking resistance is very good, essentially equivalent to stainless steel. Cold cracking, however, remains an issue, and extensive efforts are continuing to optimize composition and welding parameters, especially preheat and postweld heat treatment, to minimize its occurrence. In terms of filler metal and process development, we have progressed from sheared strip through aspiration cast rod and shielded metal arc electrodes to the point where we can now produce composite wire with a steel sheath and aluminum core in coil form, which permits the use of both the gas tungsten arc and gas metal arc processes. This is a significant advancement in that the gas metal arc process lends itself well to automated welding, and is the process of choice for commercial weld overlay applications. Using the newly developed filler metals, we have prepared clad specimens for testing in a variety of environments both in-house and outside ORNL, including laboratory and commercial organizations. As a means of assessing the field performance of this new type of material, we have modified several non-pressure boundary boiler components, including fuel nozzles and port shrouds, by introducing areas of weld overlay in strategic locations, and have placed these components in service in operating boilers for a side-by-side comparison with conventional corrosion-resistant materials.
Date: November 1, 1996
Creator: Goodwin, G.M.
Partner: UNT Libraries Government Documents Department

Hermetic packaging for microwave modules. Final report

Description: Microwave assemblies, such as radar modules, require hermetically sealed packaging. Since most of these assemblies are used for airborne applications, the packages must be lightweight. The aluminum alloy A-40 provides the needed characteristics of these applications. This project developed packaging techniques using the A-40 alloy as a housing material and laser welding processes to install connectors, purge tube, and covers on the housings. The completed package successfully passed the hermetic leak requirements and environmental testing. Optimum laser welding parameters were established in addition to all of the related tooling for assembly.
Date: October 1, 1996
Creator: Hollar, D.L.
Partner: UNT Libraries Government Documents Department

High Strength Stainless Steel Properties that Affect Resistance Welding

Description: This report discusses results of a study on selected high strength stainless steel alloy properties that affect resistance welding. The austenitic alloys A-286, JBK-75 (Modified A-286), 21-6-9, 22-13-5, 316 and 304L were investigated and compared. The former two are age hardenable, and the latter four obtain their strength through work hardening. Properties investigated include corrosion and its relationship to chemical cleaning, the effects of heat treatment on strength and surface condition, and the effect of mechanical properties on strength and weldability.
Date: August 1, 2001
Creator: Kanne, W.R.
Partner: UNT Libraries Government Documents Department

Modeling and Simulation of Microstructural Development During Weld Solidification

Description: Techniques for numerical calculations of phase transformation kinetics have recently become available. These methods are integrated with computational thermodynamics to allow for the description of diffusion-controlled transformations as a function of time. Such calculations have been applied to the modeling of solidification behavior in the current study. Three examples are considered which relate to the prediction of microstructure development and solute redistribution during conditions corresponding to welding conditions. The examples evaluate dendritic growth, planar growth, and competition between alternate solidification modes. It is shown that these techniques are particularly powerful when dealing with multi-component (>2) alloy systems. For such multi-component alloys, new considerations must be taken into account to describe the solute redistribution and the conditions leading to planar front growth. Finally, when studying global behavior covering a wide range of alloy compositions and thermal conditions, individual computations become impractical. For such calculations, neural network analysis may be beneficial and an example is given where such an analysis is shown to be suitable in describing a complex series of phase transformations.
Date: October 4, 1999
Creator: Vitek, J.M. & David, S.A.
Partner: UNT Libraries Government Documents Department

Weldability of polycrystalline aluminides. Topical report

Description: To investigate hydrogen cold cracking in iron aluminides and, specifically, to study the effect of fusion zone grain size on cracking susceptibility, welds were produced using magnetic arc oscillation to refine the fusion zone grain structures. Conventional welding produced extremely coarse columnar fusion zone grains (an average linear dimension of 530 micrometers) while welds produced with a magnetically oscillated arc contained equiaxed fusion zone grains averaging 115 micrometers in diameter. Slow strain rate tensile tests were conducted in varying water vapor atmospheres, on weldments with average fusion zone grain sizes ranging between 115 and 530 micrometers. Fracture strength and percent strain to fracture were measured for each fusion zone microstructure. The fracture strength increased in proportion to the inverse square root of the mean grain diameter, and decreased with increasing water vapor concentration. The results of the tensile tests showed that finer, equiaxed fusion zones were less susceptible to hydrogen cracking and more tolerant of high hydrogen concentrations than coarse fusion zone grain structures. Microstructural refinement via arc oscillation was also found to be suitable only for well-controlled fabrication environments.
Date: July 1, 1995
Creator: Fasching, A. A.; Edwards, G. R. & David, S. A.
Partner: UNT Libraries Government Documents Department

Laser beam welding of any metal.

Description: The effect of a metal's thermophysical properties on its weldability are examined. The thermal conductivity, melting point, absorptivity and thermal diffusivity of the metal and the laser beam focused diameter and welding speed influence the minimum beam irradiance required for melting and welding. Beam diameter, surface tension and viscosity of the molten metal affect weld pool stability and weld quality. Lower surface tension and viscosity increases weld pool instability. With larger beam diameters causing wider welds, dropout also increases. Effects of focused beam diameter and joint fitup on weldability are also examined. Small beam diameters are sensitive to beam coupling problems in relation to fitup precision in addition to beam alignment to the seam. Welding parameters for mitigating weld pool instability and increasing weld quality are derived from the above considerations. Guidelines are presented for the tailoring of welding parameters to achieve good welds. Weldability problems can also be anticipated from the properties of a metal.
Date: October 1, 1998
Creator: Leong, K. H.
Partner: UNT Libraries Government Documents Department

Investigation of Iron Aluminide Weld Overlays

Description: Conventional fossil fired boilers have been retrofitted with low NO(sub)x burners in order for the power plants to comply with new clean air regulations. Due to the operating characteristics of these burners, boiler tube sulfidation corrosion typically has been enhanced resulting in premature tube failure. To protect the existing panels from accelerated attack, weld overlay coatings are typically being applied. By depositing an alloy that offers better corrosion resistance than the underlying tube material, the wastage rates can be reduced. While Ni-based and stainless steel compositions are presently providing protection, they are expensive and susceptible to failure via corrosion-fatigue due to microsegregation upon solidification. Another material system presently under consideration for use as a coating in the oxidation/sulfidation environments is iron-aluminum. These alloys are relatively inexpensive, exhibit little microsegregation, and show excellent corrosion resistance. However, their use is limited due to weldability issues and their lack of corrosion characterization in simulated low NO(sub)x gas compositions. Therefore a program was initiated in 1996 to evaluate the use of iron-aluminum weld overlay coatings for erosion/corrosion protection of boiler tubes in fossil fired boilers with low NO(sub)x burners. Investigated properties included weldability, corrosion behavior, erosion resistance, and erosion-corrosion performance.
Date: August 2, 1999
Creator: Banovic, S.W.; DuPont, J.B.; Levin, B.F. & Marder, A.R.
Partner: UNT Libraries Government Documents Department

Synchrotron Based Observations of Sigma Phase Formation and Dissolution in Duplex Stainless Steel

Description: The formation and growth of sigma ({sigma}) phase in 2205 duplex stainless steel was observed and measured in real time using synchrotron radiation during isothermal heat treating at temperatures between 700 C and 850 C. Synchrotron experiments were performed on this material at the Advanced Photon Source (APS) while isothermally holding the samples for times of up to 10 hr. During the isothermal hold, sigma formed in quantities up to 22% as the ferrite transformed to a mixture of sigma and austenite phases. In addition, sigma formed at 850 C was heated to 1000 C to observe its dissolution. The amounts of sigma that formed, and the dissolution temperature of sigma were compared to the results predicted by Thermocalc, showing differences between the calculated and measured values. The synchrotron data was further modeled using a modified Johnson-Mehl-Avrami analysis to determine kinetic parameters for sigma formation. The initial JMA exponent, n, at low fractions of sigma was found to be approximately 7.0, however, towards the end of the transformation, n decreased to values of approximately 0.75. Because of the variable value of n, it was not possible to determine reliable values for the activation energy and pre-exponential terms for the JMA equation. During cooling to room temperature, the high temperature austenite partially transformed to ferrite, substantially increasing the ferrite content while the sigma phase kept its high temperature value.
Date: August 22, 2006
Creator: Elmer, J; Palmer, T & Specht, E
Partner: UNT Libraries Government Documents Department

Laser engineered net shaping (LENS) for the repair and modification of NWC metal components.

Description: Laser Engineered Net Shaping{trademark} (LENS{reg_sign}) is a layer additive manufacturing process that creates fully dense metal components using a laser, metal powder, and a computer solid model. This process has previously been utilized in research settings to create metal components and new material alloys. The ''Qualification of LENS for the Repair and Modification of Metal NWC Components'' project team has completed a Technology Investment project to investigate the use of LENS for repair of high rigor components. The team submitted components from four NWC sites for repair or modification using the LENS process. These components were then evaluated for their compatibility to high rigor weapons applications. The repairs included hole filling, replacement of weld lips, addition of step joints, and repair of surface flaws and gouges. The parts were evaluated for mechanical properties, corrosion resistance, weldability, and hydrogen compatibility. This document is a record of the LENS processing of each of these component types and includes process parameters, build strategies, and lessons learned. Through this project, the LENS process was shown to successfully repair or modify metal NWC components.
Date: November 1, 2006
Creator: Atwood, Clinton J.; Smugeresky, John E. (Sandia National Labs, Livermore,CA) & Gill, David Dennis
Partner: UNT Libraries Government Documents Department

Weldability Comparison of Tritium-Charged-and -Aged 304 and 316LN Stainless Steels

Description: Measurement of the effects of helium (from tritium decay) on the weldability of Types 304 and ITER Grade 316LN stainless steel demonstrated the inherent complexities in designing and conducting an experimental program using tritium-charged-and-aged materials to simulate the effects of irradiation-induced helium on weld behavior. Differences in microstructure, surface condition and alloy chemistry are known to play key roles in tritium absorption and distribution and thus have direct effects on the subsequent 3He production and distribution. The helium embrittlement cracking produced in 0.5 in. (12.7 mm) thick 304 and 316LN plates that were tritium-charged in the same container and subsequently welded with gas metal arc, low heat input weld overlays and gas tungsten arc stringer beads, varied markedly. For example, the porosity in the weld beads was much higher in the 304 plate than in the 316LN plate. Additionally, crack measurements from weld cross-sections revealed more extensive intergranular cracking in the heat-affected zones of welds on the 304 plate when compared to the 316LN plate. However, the differences between the two types of stainless steel may not be a result of differences in the resistance to helium embrittlement cracking, but may be due to initial tritium concentration differences developed in the as-charged plates. Further work is necessary to identify the reasons for the apparent plate to plate variation in tritium/helium content and to demonstrate the similarities (or differences) between Types 304 and ITER grade 316LN stainless steel.
Date: June 10, 2003
Creator: Tosten, M.H.
Partner: UNT Libraries Government Documents Department

An overview of the welding of Ni{sub 3}Al and Fe{sub 3}Al alloys

Description: Weldability (degree to which defect formation is resisted when an alloy is welded) is an issue in fabrication of Ni{sub 3}Al and Fe{sub 3}Al. Work to define and improve welding of Ni{sub 3}Al and Fe{sub 3}Al alloys is reviewed and progress illustrated by examples of current activities. The cast Ni{sub 3}Al alloys currently under development, IC221M and IC396M, have low resistance to solidification cracking and hence difficult to weld. Modifications to the composition of both base alloys and weld deposits,however, increase their resistance to cracking. Crack-free, full-penetration welds were made in centrifugally cast tubes of IC221M. Tensile and stress- rupture properties of the weldments compare favorably with base metal properties. Weldability issues have limited the use of Fe{sub 3}Al alloys to weld overlay applications. Filler metal compositions suitable for weld overlay cladding were developed, and the preheat and postweld heat treatment needed to avoid cracking, were determined experimentally.
Date: December 31, 1996
Creator: Santella, M.L.
Partner: UNT Libraries Government Documents Department

The effects of zirconium and carbon on the hot cracking resistance of iron aluminides. Topical report

Description: Iron aluminides have been of interest for about 60 years because of their good high temperature strengths (below 600{degrees}C) and excellent oxidation and sulfidation resistance, as well as their relatively low cost and conservation of strategic elements. These advantageous properties have driven the development of iron aluminides as potential structural materials. However, the industrial application of iron aluminides has been inhibited because of a sharp reduction in strength at temperatures higher than 600{degrees}C and low ductility at ambient temperatures due to hydrogen embrittlement. Oak Ridge National Laboratory has shown in recent years that room temperature properties of alloys containing 28% Al (all compositions are in atomic percent unless otherwise noted) can be improved through thermomechanical processing and alloying. Iron aluminides must have good weldability if they are to be used as structural materials. A coarse fusion zone microstructure is formed when iron aluminides are welded, increasing their susceptibility to cold cracking in water vapor. A recent study at Colorado School of Mines has shown that refining the fusion zone microstructure by weld pool oscillation effectively reduces cold cracking. Weld pool inoculation has been shown to refine fusion zone microstructures, but coarse carbide distribution caused this approach to reducing cold cracking to be ineffective.
Date: February 1, 1998
Creator: Mulac, B.L.; Edwards, G.R. & David, S.A.
Partner: UNT Libraries Government Documents Department

The effect of laser welding process parameters on the mechanical and microstructural properties of V-4Cr-4Ti structural materials.

Description: This paper reports on a systematic study which was conducted to examine the use of a pulsed Nd:YAG laser to weld sheet materials of V-Cr-Ti alloys and to characterize the microstructural and mechanical properties of the resulting joints. Deep penetration and defect-free welds were achieved under an optimal combination of laser parameters including focal length of lens, pulse energy, pulse repetition rate, beam travel speed, and shielding gas arrangement. The key for defect-free welds was found to be the stabilization of the keyhole and providing an escape path for the gas trapped in the weld. An innovative method was developed to obtain deep penetration and oxygen contamination free welds. Oxygen and nitrogen uptake were reduced to levels only a few ppm higher than the base metal by design and development of an environmental control box. Effort directed at developing an acceptable postwelding heat treatment showed that five passes of a diffuse laser beam over the welded region softened the weld material, especially in the root region of the weld.
Date: June 15, 2000
Creator: Reed, C.; Natesan, K.; Xu, Z. & Smith, D.
Partner: UNT Libraries Government Documents Department