The Experts below are selected from a list of 162 Experts worldwide ranked by ideXlab platform
Amita Mistry - One of the best experts on this subject based on the ideXlab platform.
-
the effects of short pulse laser surface cleaning on Porosity formation and reduction in laser welding of aluminium alloy for automotive component manufacture
Optics and Laser Technology, 2014Co-Authors: A. W. Alshaer, Lin Li, Amita MistryAbstract:Laser welding of aluminium alloys typically results in Porosity in the fusion zones, leading to poor mechanical and corrosion performances. Mechanical and chemical cleaning of surfaces has been used previously to remove contaminants for weld joint preparations. However, these methods are slow, ineffective (e.g. due to hydrogen trapping) or lead to environmental hazards. This paper reports the effects of short pulsed laser surface cleaning on Porosity formation and reduction in laser welding of AC-170PX (AA6014) aluminium sheets (coated with Ti/Zr and lubricated using a dry lubricant AlO70) with two types of joints: fillet edge and flange couch, using an AA4043 filler wire for automotive component assembly. The effect of laser cleaning on Porosity reduction during laser welding using a filler wire has not been reported before. In this work, Porosity and weld fusion zone geometry were examined prior to and after laser cleaning. The nanosecond pulsed Nd:YAG laser cleaning was found to Reduce Porosity significantly in the weld fusion zones. For the fillet edge welds, Porosity was Reduced to less than 0.5% compared with 10–80% without laser cleaning. For flange couch welds, Porosity was Reduced to 0.23–0.8% with laser cleaning from 0.7% to 4.3% without laser cleaning. This has been found to be due to the elimination of contaminations and oxide layers that contribute to the Porosity formation. The laser cleaning is based on thermal ablation.
-
The effects of short pulse laser surface cleaning on Porosity formation and reduction in laser welding of aluminium alloy for automotive component manufacture
Optics and Laser Technology, 2014Co-Authors: A. W. Alshaer, Amita MistryAbstract:Laser welding of aluminium alloys typically results in Porosity in the fusion zones, leading to poor mechanical and corrosion performances. Mechanical and chemical cleaning of surfaces has been used previously to remove contaminants for weld joint preparations. However, these methods are slow, ineffective (e.g. due to hydrogen trapping) or lead to environmental hazards. This paper reports the effects of short pulsed laser surface cleaning on Porosity formation and reduction in laser welding of AC-170PX (AA6014) aluminium sheets (coated with Ti/Zr and lubricated using a dry lubricant AlO70) with two types of joints: fillet edge and flange couch, using an AA4043 filler wire for automotive component assembly. The effect of laser cleaning on Porosity reduction during laser welding using a filler wire has not been reported before. In this work, Porosity and weld fusion zone geometry were examined prior to and after laser cleaning. The nanosecond pulsed Nd:YAG laser cleaning was found to Reduce Porosity significantly in the weld fusion zones. For the fillet edge welds, Porosity was Reduced to less than 0.5% compared with 10-80% without laser cleaning. For flange couch welds, Porosity was Reduced to 0.23-0.8% with laser cleaning from 0.7% to 4.3% without laser cleaning. This has been found to be due to the elimination of contaminations and oxide layers that contribute to the Porosity formation. The laser cleaning is based on thermal ablation. © 2014 Elsevier Ltd.
Anthony D. Rollett - One of the best experts on this subject based on the ideXlab platform.
-
An Investigation of Process Parameter Modifications on Additively Manufactured Inconel 718 Parts
Journal of Materials Engineering and Performance, 2018Co-Authors: Christopher Kantzos, Ross Cunningham, Sneha P. Narra, Joseph Pauza, Jack L. Beuth, Anthony D. RollettAbstract:Additive manufacturing (AM) allows for the fabrication of complex parts via layer-by-layer melting of metal powder. Laser powder-bed AM processes use a variety of process parameters including beam power, beam velocity, and hatch spacing to control melting. Alterations to these parameters have often been attempted to Reduce Porosity, for example, but less work has been done to on comprehensive effects of process parameter modifications. This study looks at the effects of altering these parameters on microstructure, Porosity, and mechanical performance of Inconel 718. The results showed that process parameter modifications that result in Porosity formation can significantly Reduce fatigue life, while microstructure changes were minimal and had little effect on tensile properties. The precipitate structure was not found to be changed significantly. These results can inform future process parameter modifications, as well as heat treatments to optimize mechanical properties.
-
Evaluating the Effect of Processing Parameters on Porosity in Electron Beam Melted Ti-6Al-4V via Synchrotron X-ray Microtomography
JOM, 2016Co-Authors: Ross Cunningham, Sneha P. Narra, Tugce Ozturk, Jack L. Beuth, Anthony D. RollettAbstract:Electron beam melting (EBM) is one of the subsets of direct metal additive manufacturing (AM), an emerging manufacturing method that fabricates metallic parts directly from a three-dimensional (3D) computer model by the successive melting of powder layers. This family of technologies has seen significant growth in recent years due to its potential to manufacture complex components with shorter lead times, Reduced material waste and minimal post-processing as a “near-net-shape” process, making it of particular interest to the biomedical and aerospace industries. The popular titanium alloy Ti-6Al-4V has been the focus of multiple studies due to its importance to these two industries, which can be attributed to its high strength to weight ratio and corrosion resistance. While previous research has found that most tensile properties of EBM Ti-6Al-4V meet or exceed conventional manufacturing standards, fatigue properties have been consistently inferior due to a significant presence of Porosity. Studies have shown that adjusting processing parameters can Reduce overall Porosity; however, they frequently utilize methods that give insufficient information to properly characterize the Porosity (e.g., Archimedes’ method). A more detailed examination of the result of process parameter adjustments on the size and spatial distribution of gas Porosity was performed utilizing synchrotron-based x-ray microtomography with a minimum feature resolution of 1.5 µm. Cross-sectional melt pool area was varied systematically via process mapping. Increasing melt pool area through the speed function variable was observed to significantly Reduce Porosity in the part.
A. W. Alshaer - One of the best experts on this subject based on the ideXlab platform.
-
the effects of short pulse laser surface cleaning on Porosity formation and reduction in laser welding of aluminium alloy for automotive component manufacture
Optics and Laser Technology, 2014Co-Authors: A. W. Alshaer, Lin Li, Amita MistryAbstract:Laser welding of aluminium alloys typically results in Porosity in the fusion zones, leading to poor mechanical and corrosion performances. Mechanical and chemical cleaning of surfaces has been used previously to remove contaminants for weld joint preparations. However, these methods are slow, ineffective (e.g. due to hydrogen trapping) or lead to environmental hazards. This paper reports the effects of short pulsed laser surface cleaning on Porosity formation and reduction in laser welding of AC-170PX (AA6014) aluminium sheets (coated with Ti/Zr and lubricated using a dry lubricant AlO70) with two types of joints: fillet edge and flange couch, using an AA4043 filler wire for automotive component assembly. The effect of laser cleaning on Porosity reduction during laser welding using a filler wire has not been reported before. In this work, Porosity and weld fusion zone geometry were examined prior to and after laser cleaning. The nanosecond pulsed Nd:YAG laser cleaning was found to Reduce Porosity significantly in the weld fusion zones. For the fillet edge welds, Porosity was Reduced to less than 0.5% compared with 10–80% without laser cleaning. For flange couch welds, Porosity was Reduced to 0.23–0.8% with laser cleaning from 0.7% to 4.3% without laser cleaning. This has been found to be due to the elimination of contaminations and oxide layers that contribute to the Porosity formation. The laser cleaning is based on thermal ablation.
-
The effects of short pulse laser surface cleaning on Porosity formation and reduction in laser welding of aluminium alloy for automotive component manufacture
Optics and Laser Technology, 2014Co-Authors: A. W. Alshaer, Amita MistryAbstract:Laser welding of aluminium alloys typically results in Porosity in the fusion zones, leading to poor mechanical and corrosion performances. Mechanical and chemical cleaning of surfaces has been used previously to remove contaminants for weld joint preparations. However, these methods are slow, ineffective (e.g. due to hydrogen trapping) or lead to environmental hazards. This paper reports the effects of short pulsed laser surface cleaning on Porosity formation and reduction in laser welding of AC-170PX (AA6014) aluminium sheets (coated with Ti/Zr and lubricated using a dry lubricant AlO70) with two types of joints: fillet edge and flange couch, using an AA4043 filler wire for automotive component assembly. The effect of laser cleaning on Porosity reduction during laser welding using a filler wire has not been reported before. In this work, Porosity and weld fusion zone geometry were examined prior to and after laser cleaning. The nanosecond pulsed Nd:YAG laser cleaning was found to Reduce Porosity significantly in the weld fusion zones. For the fillet edge welds, Porosity was Reduced to less than 0.5% compared with 10-80% without laser cleaning. For flange couch welds, Porosity was Reduced to 0.23-0.8% with laser cleaning from 0.7% to 4.3% without laser cleaning. This has been found to be due to the elimination of contaminations and oxide layers that contribute to the Porosity formation. The laser cleaning is based on thermal ablation. © 2014 Elsevier Ltd.
Bikiran Goswami - One of the best experts on this subject based on the ideXlab platform.
-
Applications of thermal barrier coating system in gas turbines - A review
2004Co-Authors: A. K. Ray, Bikiran GoswamiAbstract:Ceramic coatings are refractory metal oxides deposited on substrate to Reduce thermal loss and to protect components, being operuted at high temperature. Thermal barrier coatings (TBC) are composite overlay of bond coat and ceramic coat on a superallor substrate implemented in combustion engines. Thermal and mechanical strains of service exposure requires structural compliance tolerances. This is facilitated by brittle constituent deposition technique over a ductile substrate. Electron beamphysical vapour deposition and plasma spray technique provides this from tortuous intergrunular network of coating. Porous deposition technique is applied in most cases instead of cementation or continuous section thickness. Thermal barrier coating is inevitable in aerospace engine sections operating at limiting conditions of strains. This is attributed to reduction of temperature levels and grat1iets.Subsequent advantages are protection of high temperature components for maximum utilisation of component lives and maximum utilisation of energy by operating at optimum allowable temperature limits. Thermo-mechanical behaviour of TBC is optimised by ill-situ formation and transformation mechanisms of alumina from aluminium of substrate/bond coat and metastable tetragonal zirconia to stable tetmgonal zirconia respectively at temperature of service. The former produces a volumetric contraction whereas later produces volumetric expansion. In service the composite system provides an auto-toughening effects in due courses. Mechanical behaviour of TBC is attributed to the intergranular tortuous network. This on strain exposure form cracks and at the second stage of crack tip blunting form cubic allotropy from metastable tetragonal phase. Reduction of cia ratio thus increases toughness. However a prolonged exposure form localised spallation zones being initiated by volumetric expansion stresses associated with nickel enrichment of thermally grown oxides (TBC) at bond coat/ceramic coat interface and auto-sintering. TBC interaction directly with substrate is a wide variation of ductility. So bond coat is applied to produce mechanical adherence and stress relaxation effects. Generally M-CrAIY family of bond coating alloys are used. Exposure to operatingltest temperature produces thermally grown oxides (TGO) at interface. This occupies an intermediate zone in response to property interactions. TGO mainly consists of alumina being catalysed by chromia and adhered by yttria. Current scenario is to study contmdiction between auto-sintering and auto-toughening mechanisms and to decrease effects of thermal expansion mismatch stresses by application of composite coatings made from functionally graded materials microlaminated,and multilayeredceramic/ceramicor metallic/ceramicor metallic/metallic coatings. Application of laser scaling or remelting to Reduce Porosity of free surface and to increase glaze is another avenues to Reduce diffusion of reactive gases and to increase internal heat transfer respectively. The former state increases life of bond coat/substrate, where as later increase energy efficiency by maximu mutilisation of heat.The main unsolved problems are spallation of ceramic coating being cohesively induced in either side of interface and spread out to interfacesof adhesion. TBC increase life more than twice for cases of aerospace engines however localised spallation by high temperature corrosion of bond coat/substrate, TGO stresses, gaseous/liquid contaminant diffusion/impregnation through tolerance networking of voids. erosion and their addItive effects increase pressure over preventive measure.
-
Thermal Barrier Coating System for Gas Turbine Application- A Review
High Temperature Materials and Processes, 2003Co-Authors: Bikiran Goswami, A. K. Ray, Sanjay K. SahayAbstract:Ceramic coatings are refractory metal compounds deposited on substrates to Reduce thermal loss and to protect components from high temperature. Thermal barrier coatings (TBC) are composite overlay of bond coat and ceramic coat on a superalloy substrate. Atomised deposition or splat deposition of fine semi-molten particle technique deposits thin coatings of brittle ceramic. Thermal and mechanical strains arising from service exposure require structural compliance tolerances. This is facilitated by brittle constituent deposition over a ductile substrate. Electron beam physical vapour deposition and plasma spray technique lead to a tortuous intergranular network of coating. Porous deposition technique is applied in all cases instead of cementation or continuous section thickness. Thermal barrier coating is inevitable in aerospace engine sections operating at limiting conditions of strains. Thermal barrier coatings help in protection of high temperature components for maximum utilisation of component lives, and maximum utilisation of energy by operating at optimum allowable temperature limits. Thermo mechanical behaviour of TBC is optimised by in-situ formation and transformation mechanisms of alumina from aluminium of substrate/bondcoat and metastable tetragonal zirconia to stable tetragonal zirconia respectively at temperature of service. While the former produces a volumetric contraction, the latter produces volumetric expansion. In service the composite system provides auto-toughening effects in due course. An intergranular tortuous network of coating forms cracks on exposure of strain and the crack tip blunting forms cubic allotropy from metastable tetragonal phase, resulting in an increase in toughness due to elimination of c/a ratio. However, a prolonged exposure forms localised spallation zones, which are initiated by volumetric expansion stresses associated with nickel enrichment of thermally grown oxides (TGO) at bond coat/ceramic coat interface, and auto-sintering. Bond coat is applied to produce mechanical adherence and stress relaxation effects. Generally M-CrAlY families of bond coating alloys are used for this purpose. Exposure to operating/test temperature produces thermally grown oxides (TGO) at interface. This occupies an intermediate zone in response to property interactions. TGO mainly consists of alumina being catalyzed by chromia and adhered by yttria. Active research is going on to study the mechanisms of auto sintering and auto-toughening of TBC. Work is in progress to explore how to decrease thermal expansion mismatch stresses by application of composite coatings made from functionally graded materials, microlaminated, and multilayered ceramic/ ceramic or metallic/ceramic or metallic/metallic coatings. The application of laser scaling or remelting to Reduce Porosity of free surface and to increase glaze are other avenues to Reduce diffusion of reactive gases and to increase internal heat transfer respectively. The former increases life of bond coat/substrate, whereas the latter increases energy efficiency by maximum utilisation of heat. The main unsolved problem is spallation of ceramic coating, which is cohesively induced in either side of interface and spread out to interfaces of adhesion. TBC increases life more than two-fold for cases of aerospace engines. However localised spallation may rise by high temperature corrosion of bond coat/substrate, TGO stresses, gaseous/liquid contaminant diffusion/ impregnationthrough tolerance networking of voids, and erosion.
Lin Li - One of the best experts on this subject based on the ideXlab platform.
-
the effects of short pulse laser surface cleaning on Porosity formation and reduction in laser welding of aluminium alloy for automotive component manufacture
Optics and Laser Technology, 2014Co-Authors: A. W. Alshaer, Lin Li, Amita MistryAbstract:Laser welding of aluminium alloys typically results in Porosity in the fusion zones, leading to poor mechanical and corrosion performances. Mechanical and chemical cleaning of surfaces has been used previously to remove contaminants for weld joint preparations. However, these methods are slow, ineffective (e.g. due to hydrogen trapping) or lead to environmental hazards. This paper reports the effects of short pulsed laser surface cleaning on Porosity formation and reduction in laser welding of AC-170PX (AA6014) aluminium sheets (coated with Ti/Zr and lubricated using a dry lubricant AlO70) with two types of joints: fillet edge and flange couch, using an AA4043 filler wire for automotive component assembly. The effect of laser cleaning on Porosity reduction during laser welding using a filler wire has not been reported before. In this work, Porosity and weld fusion zone geometry were examined prior to and after laser cleaning. The nanosecond pulsed Nd:YAG laser cleaning was found to Reduce Porosity significantly in the weld fusion zones. For the fillet edge welds, Porosity was Reduced to less than 0.5% compared with 10–80% without laser cleaning. For flange couch welds, Porosity was Reduced to 0.23–0.8% with laser cleaning from 0.7% to 4.3% without laser cleaning. This has been found to be due to the elimination of contaminations and oxide layers that contribute to the Porosity formation. The laser cleaning is based on thermal ablation.
-
Evaluation of five strategies to limit the impact of fouling in permeable reactive barriers.
Journal of hazardous materials, 2010Co-Authors: Lin Li, Craig H BensonAbstract:Ground water flow and geochemical reactive transport models were used to assess the effectiveness of five strategies used to limit fouling and to enhance the long-term hydraulic behavior of continuous-wall permeable reactive barriers (PRBs) employing granular zero valent iron (ZVI). The flow model accounted for geological heterogeneity and the reactive transport model included a geochemical algorithm for simulating iron corrosion and mineral precipitation reactions that have been observed in ZVI PRBs. The five strategies that were evaluated are pea gravel equalization zones, a sacrificial pre-treatment zone, pH adjustment, large ZVI particles, and mechanical treatment. Results of simulations show that installation of pea gravel equalization zones results in flow equalization and a more uniform distribution of residence times within the PRB. Residence times within the PRB are less affected by mineral precipitation when a pre-treatment zone is employed. pH adjustment limits the total amount of hydroxide ions in ground water to Reduce Porosity reduction and to retain larger residence times. Larger ZVI particles Reduce Porosity reduction as a result of the smaller iron surface area for iron corrosion, and retain longer residence time. Mechanical treatment redistributes the Porosity uniformly throughout the PRB over time, which is effective in maintaining residence time.