Welding Metallurgy of
01 Jan 1987-
About: The article was published on 1987-01-01 and is currently open access. It has received 991 citations till now. The article focuses on the topics: Welding.
Citations
More filters
TL;DR: In this paper, a study of the power beam welding of two precipitation strengthened nickel base superalloys, Waspaloy and Udimet 720Li, which are widely used in the gas turbine industry is presented.
Abstract: A study is presented of the power beam welding of two precipitation strengthened nickel base superalloys, Waspaloy and Udimet 720Li, which are widely used in the gas turbine industry. Processing was carried out on 4·3 mm thickness rectilinear sections using (i) an electron beam welding apparatus operating at 150 kV and 12 mA, and (ii) a Nd-YAG laser capable of delivering 3·5 kW at the workpiece. The laser beam welds yielded 'hourglass shaped' fusion profiles, due to the blooming of the laser beam; conversely, the profiles of the electron beam welds were very much more uniform. Radiography indicated considerable porosity in the laser welds, which was attributed to the entrapment of gases due to keyhole collapse. In Waspaloy, the fusion zone was about 40% softer than the baseplate following welding; in contrast, the Udimet 720Li fusion zone was about 15% harder. This was attributed to the different equilibrium fractions of the γ' phase, and the lack of any detectable in weld γ' precipitation in Wasp...
26 citations
TL;DR: In this paper, the nickel-plated carbon nanotubes composite inconel718 alloy coatings were prepared on 304 stainless steel by laser melting deposition and its properties of microstructure, wear resistance and corrosion resistance were studied.
Abstract: Nickel-plated carbon nanotubes composite inconel718 alloy coatings were prepared on 304 stainless steel by laser melting deposition. Its properties of microstructure, wear resistance and corrosion resistance were studied. In the inconel718 coating, the phases are γ-(Ni, Fe), γ′-Ni (Al, Ti) and Fe3Ni2. Compared with the coating without nickel-plated carbon nanotubes, the new phases are C, (Fe, C), C70 and Fe5C2, the grain structure is more uniform, the number of cracks is less and the length of cracks is shorter, the hardness is reduced by 21%, the self-corrosion potential is decreased by 4.4%, the corrosion current density is increased by 47%, the polarization resistance is decreased by 44%, the friction coefficient increases by 18% and the mass wear increases by 83%.
26 citations
TL;DR: In this article, a small addition of scandium to the commercial 7010 alloy reduces the hot cracking susceptibility during solidification of welds produced by the gas tungsten arc welding process.
Abstract: The commercial 7000 series aluminium alloys are based on medium strength Al–Zn–Mg and high strength Al–Zn–Mg–Cu systems. The medium strength alloys are weldable, whereas the high strength alloys are non-weldable. This is because the amount of copper present in these alloys gives rise to hot cracking during solidification of welds. As a result, the high strength Al–Zn–Mg– Cu base alloys are not used for applications where joining of components by welding is an essential step. In the present study, using a combination of qualitative Houldcroft test and quantitative Varestraint test, it is shown that a small addition of scandium to the commercial 7010 alloy reduces the hot cracking susceptibility during solidification of welds produced by the gas tungsten arc welding process. The improvement in weldability is found to be the result of the considerable grain refinement in the weld structure following the scandium addition. The results of microhardness and tensile tests are further described within the...
26 citations
Cites background from "Welding Metallurgy of"
...Among the weldable and heat treatable alloys, medium strength Al–Zn–Mg alloys are being employed extensively in the manufacture of components for aircraft and space crafts in view of their corrosion resistance and ease of fabrication.(3) In recent years, the aeronautical community has renewed attention to reducing the weight of components by using very high strength aluminium alloys....
[...]
...These problems are greater in Mg containing 2000 series and Cu containing 7000 series aluminium alloys.(3) Among the weldable and heat treatable alloys, medium strength Al–Zn–Mg alloys are being employed extensively in the manufacture of components for aircraft and space crafts in view of their corrosion resistance and ease of fabrication....
[...]
TL;DR: In this article, a simplified macroscopic and semi-analytical thermal analysis of directed energy deposition (DED) is presented to obtain computationally efficient simulations of the entire process, where solidification and solid-state phase transitions are taken into account.
Abstract: In this contribution, a simplified macroscopic and semi-analytical thermal analysis of directed energy deposition (DED) is presented to obtain computationally efficient simulations of the entire process. Solidification and solid-state phase transitions are taken into account. The model is derived for laser metal powder directed energy deposition, although it can be simply adapted for other focused thermal energy (e.g., electron beam, or plasma arc). The gas flow used for carrying the powder significantly influences cooling conditions, which is included in the model. The proposed simulation strategy applies to multilayer composites with a wide range of shapes in the horizontal plane and arbitrary laser scanning strategies (continuous way, back and forth, etc.). The proposed work provides a simple tool to study the influence of most process parameters, design in situ experiments and in turn develop optimization loops to reach material requirements and specific microstructures. In situ pyrometer measurements have been compared to the model, and good agreement has been observed with 2.6% error in average. The model is used to demonstrate the effect of various process parameters for a simple cylindrical geometry and a more complex auxetic cell.
26 citations
Cites background from "Welding Metallurgy of"
...Moreover, dwell times have an effect on the direction of crystallization mostly aligned with the temperature gradient [52, 53]....
[...]
TL;DR: In this article, the authors examine and quantify these issues in detail, thus providing the reader with an appreciation of all things that must be considered when preparing a standardized procedure for weldability testing.
Abstract: Industry and research have long desired the establishment of standards for weldability testing in regards to hydrogen-assisted cold cracking formation. This would have the obvious advantage of allowing data to be reliably compared between different research labs. But making decisions regarding standards requires some careful thought and agreement on i) how test parameters affect test results, ii) what exactly needs to be measured, and iii) how test results should be interpreted and reported. Our depth of understanding on these points has matured significantly over time and, while there is not always universal agreement, it is at least possible to start highlighting factors important to standards. This paper examines these factors, including the welding parameters, restraint, hydrogen, and cracking index. When comparing different alloys having different thermal characteristics, the use of constant welding parameters (common practice) will result in variable weld penetration and weld pool shape, which can influence grain shape and microstructural features, which can result in inequitable weldability comparisons. Welding on test coupons having different dimensions can affect restraint, which will influence the residual stresses around the weldment. High restraint usually results in higher crack susceptibility. Also, hydrogen content present in a weldment depends on the thermal history, welding parameters, and surrounding atmosphere humidity, with high hydrogen contents associated to great cracking susceptibility. Finally, the selection of an appropriate cracking index is required for data analysis. Quantifications of crack length and minimum preheat temperature are common indexes used for comparison. Critical stress and hydrogen content are other indexes. But how well these indexes actually represent weldability are contentious issues. This paper will examine and quantify these issues in detail, thus providing the reader with an appreciation of all things that must be considered when preparing a standardized procedure for weldability testing.
25 citations
References
More filters
TL;DR: In this article, the state of the art in selective laser sintering/melting (SLS/SLM) processing of aluminium powders is reviewed from different perspectives, including powder metallurgy (P/M), pulsed electric current (PECS), and laser welding of aluminium alloys.
1,172 citations
TL;DR: In this article, the authors show that the pre-existing dislocation network, which maintains its configuration during the entire plastic deformation, is an ideal modulator that is able to slow down but not entirely block the dislocation motion.
557 citations
TL;DR: In this article, the fundamental understanding of structure-properties relationship in automotive steels resistance spot welds is discussed. And a brief review of friction stir spot welding, as an alternative to RSW, is also included.
Abstract: Spot welding, particularly resistance spot welding (RSW), is a critical joining process in automotive industry. The development of advanced high strength steels for applications in automotive industry is accompanied with a challenge to better understand the physical and mechanical metallurgy of these materials during RSW. The present paper critically reviews the fundamental understanding of structure–properties relationship in automotive steels resistance spot welds. The focus is on the metallurgical characteristics, hardness–microstructure correlation, interfacial to pullout failure mode transition and mechanical performance of steel resistance spot welds under quasi-static, fatigue and impact loading conditions. A brief review of friction stir spot welding, as an alternative to RSW, is also included.
369 citations
TL;DR: In this article, a unified equation to compute the energy density is proposed to compare works performed with distinct equipment and experimental conditions, covering the major process parameters: power, travel speed, heat source dimension, hatch distance, deposited layer thickness and material grain size.
369 citations
TL;DR: This study attempted to predict solidification defects by DNN regression with a small dataset that contains 487 data points and found that a pre-trained and fine-tuned DNN shows better generalization performance over shallow neural network, support vector machine, and DNN trained by conventional methods.
314 citations