Effect of interpass temperature on the structure and properties of multipass weldments in high performance nickel alloys

2011 Summer.Includes bibliographical references.Nickel alloys comprise an important group of engineering materials which are used primarily for their exceptional resistance to corrosion and their ability to maintain good mechanical strength over a wide temperature range, (both low and high) in demanding industrial applications. Welding is a primary fabrication process for these alloys. It has been a generally accepted practice to maintain a maximum interpass temperature of 200°F or lower when multipass welding many nickel alloys to prevent defects such as cracking or loss of corrosion resistance. This practice has been based on recommendations by many of the nickel alloy producers. A low maximum interpass temperature can increase the welding time which increases fabrication costs. According to the author's industry contacts and based upon the author's industrial experience as well as the author's examination of the literature, there has been little or no systematic research on the effect of interpass temperature for multipass welding of nickel alloys. In fact, the same is true for the establishment of the basic robotic welding parameters using the new generation of digital power supplies for these alloys. This dissertation presents research on the effect of interpass temperature on two nickel alloys; HASTELLOY® C-2000® and HASTELLOY® B-3®. Welding parameters were also developed for these alloys and also for HAYNES® 230® alloy using Gas Metal Arc Welding, GMAW, as a single process for both the root and fill weld passes. Weldments were made at 5 different interpass temperatures, 100°F - 500°F, in 100°F increments, for these alloys in thicknesses of 0.25 inch and 0.5 inch. Transverse weld specimens were then tested according to AWS B4.0:2007 using tensile, bend, and hardness tests. Transverse weld specimens were corrosion tested according to ASTM G28A for the HASTELLOY C-2000 alloy and the HASTELLOY B-3 alloy was subjected to 20% HCl at 149°C for 96 hours in an autoclave. The specimens were also examined using optical light microscopy for intergranular corrosion attack, weld fusion, cracking, and heat affected zone (HAZ) microstructure effects. (HASTELLOY, HAYNES, C-2000, B-3, and 230 are registered trademarks of Haynes International, Inc.) No significant loss of tensile strength was found at any of the higher interpass temperatures. All ultimate tensile strengths for both alloys were above the ASME Boiler and Pressure Vessel Code Section IX minimum. All samples passed 2T transverse face bend tests. Some lack of fusion was observed at the root of some samples at random interpass temperatures. No noticeable change in the HAZ microstructure or cracking was observed at the highest interpass temperature for both the HASTELLOY C-2000 and the HASTELLOY B-3 alloys. No significant corrosion attack was found along the weld, face or root sides, for both alloys at the higher interpass temperature of 500°F. It was concluded that a higher interpass temperature could be specified for these alloys without any appreciable loss of strength, weld soundness, loss of corrosion resistance, or detrimental effect to microstructure. It was also shown that the GMAW process could be used as a sole welding process but more development is needed to decrease process variability in the root pass and to develop a complete welding procedure specification

A New Era in Extragalactic Background Light Measurements: The Cosmic History of Accretion, Nucleosynthesis and Reionization

(Brief Summary) What is the total radiative content of the Universe since the epoch of recombination? The extragalactic background light (EBL) spectrum captures the redshifted energy released from the first stellar objects, protogalaxies, and galaxies throughout cosmic history. Yet, we have not determined the brightness of the extragalactic sky from UV/optical to far-infrared wavelengths with sufficient accuracy to establish the radiative content of the Universe to better than an order of magnitude. Among many science topics, an accurate measurement of the EBL spectrum from optical to far-IR wavelengths, will address: What is the total energy released by stellar nucleosynthesis over cosmic history? Was significant energy released by non-stellar processes? Is there a diffuse component to the EBL anywhere from optical to sub-millimeter? When did first stars appear and how luminous was the reionization epoch? Absolute optical to mid-IR EBL spectrum to an astrophysically interesting accuracy can be established by wide field imagingat a distance of 5 AU or above the ecliptic plane where the zodiacal foreground is reduced by more than two orders of magnitude.Comment: 7 pages; Science White Paper for the US Astro 2010-2020 Decadal Survey. If interested in further community-wide efforts on this topic please contact the first autho

Radio Astronomy

Contains research objectives, summary of research and reports on eleven research projects.National Aeronautics and Space Administration (Grant NGL 22-009-016)National Science Foundation (Grant GP-14854)Joint Services Electronics Programs (U. S. Army, U. S. Navy, and U. S. Air Force) under Contract DA 28-043-AMC-02536(E)National Science Foundation (Grant GP-13056)Sloan Fund for Basic Research (M. I. T. Grant 312

Radio Astronomy

Contains table of contents for Section 4 and reports on nine research projects.National Science Foundation Grant AST 88-19848National Science Foundation Grant AST 90-22501Alfred P. Sloan FellowshipNational Science Foundation Presidential Young Investigator AwardNational Aeronautics and Space Administration Grant NAGW-2310David and Lucile Packard FellowshipSM Systems and Research CorporationNational Aeronautics and Space Administration/Goddard Space Flight Center Contract NAS 5-30791National Aeronautics and Space Administration/Goddard Space Flight Center Grant NAG5-10Leaders for Manufacturing Progra

Origins Space Telescope: Baseline mission concept

The Origins Space Telescope will trace the history of our origins from the time dust and heavy elements permanently altered the cosmic landscape to present-day life. How did galaxies evolve from the earliest galactic systems to those found in the Universe today? How do habitable planets form? How common are life-bearing worlds? To answer these alluring questions, Origins will operate at mid-and far-infrared (IR) wavelengths and offer powerful spectroscopic instruments and sensitivity three orders of magnitude better than that of the Herschel Space Observatory, the largest telescope flown in space to date. We describe the baseline concept for Origins recommended to the 2020 US Decadal Survey in Astronomy and Astrophysics. The baseline design includes a 5.9-m diameter telescope cryocooled to 4.5 K and equipped with three scientific instruments. A mid-infrared instrument (Mid-Infrared Spectrometer and Camera Transit spectrometer) will measure the spectra of transiting exoplanets in the 2.8 to 20 μm wavelength range and offer unprecedented spectrophotometric precision, enabling definitive exoplanet biosignature detections. The far-IR imager polarimeter will be able to survey thousands of square degrees with broadband imaging at 50 and 250 μm. The Origins Survey Spectrometer will cover wavelengths from 25 to 588 μm, making wide-area and deep spectroscopic surveys with spectral resolving power R ∼ 300, and pointed observations at R ∼ 40,000 and 300,000 with selectable instrument modes. Origins was designed to minimize complexity. The architecture is similar to that of the Spitzer Space Telescope and requires very few deployments after launch, while the cryothermal system design leverages James Webb Space Telescope technology and experience. A combination of current-state-of-the-art cryocoolers and next-generation detector technology will enable Origins\u27 natural background-limited sensitivity

Apophis planetary defense campaign

We describe results of a planetary defense exercise conducted during the close approach to Earth by the near-Earth asteroid (99942) Apophis during 2020 December–2021 March. The planetary defense community has been conducting observational campaigns since 2017 to test the operational readiness of the global planetary defense capabilities. These community-led global exercises were carried out with the support of NASA's Planetary Defense Coordination Office and the International Asteroid Warning Network. The Apophis campaign is the third in our series of planetary defense exercises. The goal of this campaign was to recover, track, and characterize Apophis as a potential impactor to exercise the planetary defense system including observations, hypothetical risk assessment and risk prediction, and hazard communication. Based on the campaign results, we present lessons learned about our ability to observe and model a potential impactor. Data products derived from astrometric observations were available for inclusion in our risk assessment model almost immediately, allowing real-time updates to the impact probability calculation and possible impact locations. An early NEOWISE diameter measurement provided a significant improvement in the uncertainty on the range of hypothetical impact outcomes. The availability of different characterization methods such as photometry, spectroscopy, and radar provided robustness to our ability to assess the potential impact risk

Advancing Science of the Moon: Progress Toward Achieving the Goals of the Scientific Context for Exploration of the Moon Report

No abstract availabl