Effects of electron beam oscillation techniques on solidification behaviour and stress rupture properties of Inconel 718 welds
01 Feb 2007-Science and Technology of Welding and Joining (Taylor & Francis)-Vol. 12, Iss: 2, pp 106-114
TL;DR: In this article, the effects of electron beam oscillation techniques (sinusoidal, square, triangular, ramp, circle and elliptical) in controlling Nb segregation, Laves formation and stress rupture behaviour of Inconel 718 electron beam welds are studied.
Abstract: Effects of electron beam oscillation techniques (sinusoidal, square, triangular, ramp, circle and elliptical) in controlling Nb segregation, Laves formation and stress rupture behaviour of Inconel 718 electron beam welds are studied. Effects of various post-weld heat treatments on stress rupture behaviour are compared. Elliptical beam oscillation technique resulted in less Nb segregation and discontinuous and fine Laves in the interdendritic regions compared with other welds and unoscillated beam weld. Response to aging was better for welds made with elliptical oscillated beam compared with welds made with unoscillated beam. Oscillated beam welds exhibited longer rupture life than unoscillated beam welds in both solution treated and aged and directly aged conditions.
Citations
More filters
TL;DR: In this article, three beam oscillating patterns that are transversal, longitudinal and circular were studied to join 4mm-thick AA6061-T6 aluminum alloy in butt configuration.
188 citations
TL;DR: Inconel 718 is a nickel-ferrous-chromium based superalloy extensively used in the aerospace sector at elevated temperature up to 650°C due to its better mechanical properties and weldability as discussed by the authors.
51 citations
TL;DR: In this article, the aging behavior of the joint is influenced by low Nb+Al+Ti content of isothermal solidification zone (ISZ) and formation of Nb-Cr-Mo based boride precipitates in diffusion affected zone (DAZ).
Abstract: Aging response of transient liquid phase Nb bearing wrought IN718 nickel base superalloy is studied. The aging behaviour of the joint is influenced by low Nb+Al+Ti content of isothermal solidification zone (ISZ) and formation of Nb–Cr–Mo based boride precipitates in diffusion affected zone (DAZ). It was shown that applying a post-bond heat treatment which was able to eliminate the diffusion induced boride precipitates in DAZ and increase the Nb+Al+Ti content of the ISZ improved the aging response and shear strength of the joint.
31 citations
TL;DR: In this article, the properties of electron beam-welded AISI 316L stainless steel butt joints with and without beam oscillation were evaluated by microstructural analysis, mechanical testing like microhardness measurements, tensile tests at room and elevated temperature 973 K (700°C), three-point bend, and Charpy impact tests.
Abstract: The properties of electron beam-welded AISI 316L stainless steel butt joints prepared with and without beam oscillation were evaluated by microstructural analysis, mechanical testing like microhardness measurements, tensile tests at room and elevated temperature 973 K (700 °C), three-point bend, and Charpy impact tests. All joints, irrespective of being prepared with or without beam oscillation, were found to be defect free. Welds produced by beam oscillation exhibited narrower fusion zone (FZ) with lathy ferrite morphology, while the weld without beam oscillation was characterized by wider FZ and skeletal ferrite morphology. During tensile tests at room and elevated temperature 973 K (700 °C), all samples fractured in the base metal (BM) and showed almost the same tensile properties as that of the BM. However, the notch tensile tests at room temperature demonstrated higher strength for joints prepared with the oscillating beam. Besides, face and root bend tests, as well as Charpy impact tests, showed higher bending strength and notch toughness, respectively, for joints prepared with beam oscillation.
31 citations
References
More filters
01 Jan 1987
991 citations
"Effects of electron beam oscillatio..." refers background in this paper
...Sufficient increase in the degree of undercooling (by having lower G/R) can alter the solidification mode from columnar dendritic to equiaxed dendritic.(18) Under the unoscillated welding conditions, the steep thermal gradients inherent in the process (because of extremely localised heating) result in higher G/R ratios and favour columnar growth from the fusion boundaries....
[...]
TL;DR: In this article, the authors describe the characteristic defects found as a result of welding the more difficult, highly alloyed materials and review a number of welding processes used in the manufacture and repair of nickel alloy components.
Abstract: The continued drive for increased efficiency, performance and reduced costs for industrial gas turbine engines demands extended use of high strength-high temperature capability materials, such as nickel based superalloys. To satisfy the requirements of the component design and manufacturing engineers, these materials must be capable of being welded in a satisfactory manner. The present paper describes the characteristic defects found as a result of welding the more difficult, highly alloyed materials and reviews a number of welding processes used in the manufacture and repair of nickel alloy components. These include gas tungsten arc (GTA) and electron beam (EB) welding, laser powder deposition and friction welding. Many of the more dilute nickel based alloys are readily weldable using conventional GTA processes; however, high strength, precipitation hardened materials are prone to heat affected zone and strain age cracking defect formation. A number of factors are found to affect the propensity f...
365 citations
TL;DR: Pulsed Nd-YAG laser welding characteristics of Inconel 718 sheet material (2.mm thick) were investigated in this article, where Weld microstructures and room temperature tensile properties were evaluated.
221 citations
TL;DR: In this paper, an attempt was made to control the formation of Laves phase in alloy 718 gas tungsten arc welds using pulsed current, and the results show that the use of current pulsing refines the fusion zone microstructure, reduces the amount of laves phase and exerts a favourable influence on its morphology and improves the response of the fusion zones to post-weld heat treatment and weld tensile properties.
Abstract: The presence of Nb rich Laves phase in Inconel 718 weld fusion zones is known to be detrimental to weld mechanical properties. In the present study, an attempt was made to control the formation of Laves phase in alloy 718 gas tungsten arc welds using pulsed current. Welds were produced in 2 mm thick sheets of the alloy with constant current and pulsed current and were subjected to post-weld solution treatment at 980°C followed by aging. Detailed microstructural studies and tensile tests at 650°C were conducted. The results show that the use of current pulsing (i) refines the fusion zone microstructure, (ii) reduces the amount of Laves phase and exerts a favourable influence on its morphology and (iii) improves the response of the fusion zone to post-weld heat treatment and weld tensile properties.
168 citations
TL;DR: In this article, the formation of laves phase in high heat input gas tungsten arc (GTA) and low heat input electron beam (EB) welds of 2 mm thick superalloy 718 in as-welded and postweld heat treated (PWHT) conditions is evaluated.
Abstract: The important consequence of the solidification in cast or welded superalloy 718 is the segregation of Nb and the formation of laves phase. Laves phase is a brittle intermetallic topologically close-packed phase with hexagonal structure, known for its detrimental effect on mechanical properties at room temperature [1]. Although data available with regard to wrought materials is somewhat elaborate it is not true for welds in general and for electron beam welds in particular. In this letter the formation of laves phase in high heat input gas tungsten arc (GTA) and low heat input electron beam (EB) welds of 2 mm thick superalloy 718 in as-welded and post-weld heat treated (PWHT) conditions is evaluated. The results have a bearing on the tensile ductility and other properties of welds. Sheets of superalloy 718 of thickness 2 mm in solution treated condition (chemical composition in Table I) were autogenously welded by automatic GTA and EB welding processes, resulting in full penetration using the weld process parameters listed in Table II. The as-welded samples were subjected to two PWHT schedules: direct duplex ageing and solution treatment followed by ageing. Solution treatment was carried out at 980 °C for 20 rain with air cooling and the duplex ageing was carried out at 720 °C for 8 h with furnace cooling to 620 °C for 8 h with air cooling. The as-welded and heat treated samples were then subjected to scanning electron microscopic (SEM) examination and quantitative electron probe micro-analysis (EPMA) for the analysis of microsegregation of elements and determination of the formation of laves phase. Figs 1 and 2 show SEM micrographs of the aswelded microstructures of EB and GTA weld metals, respectively. Essentially, the solidified structure is of dendritic type. EB weld metal showed relatively finer
60 citations