| 1. |
- Singh, Sukhdeep, 1988, et al.
(författare)
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Influence of homogenisation treatments on the hot ductility of cast ATI® 718Plus®: Effect of niobium and minor elements on liquation characteristics
- 2021
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Ingår i: Materials Science & Engineering A: Structural Materials: Properties, Microstructure and Processing. - : Elsevier BV. - 0921-5093 .- 1873-4936. ; 799
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Tidskriftsartikel (refereegranskat)abstract
- The hot ductility of cast ATI® 718Plus® was assessed using the Gleeble thermo-mechanical simulator after being subjected to different homogenisation heat treatments. The hot ductility deteriorated significantly after long-dwell homogenisation heat treatments for 24 h at temperatures of 1120 and 1190 °C as compared with those treated at a short dwell time of 4 h at the same temperatures. The observed ductility deterioration was related to more extensive liquation along the grain boundaries caused by different mechanisms, e.g., liquation by solute segregation mechanism, Laves melting, constitutional liquation of MC carbides and supersolidus grain boundary melting, with the effect and extent depending on the solute changes after the homogenisation heat treatments. Furthermore, the role of Nb as the solute element and as the precipitate former, as well as the effect of minor alloying elements segregating along the grain boundaries, is discussed in connection to grain boundary liquation, which contributes to a better understanding of heat-affected zone liquation cracking susceptibility of cast ATI® 718Plus®.
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| 2. |
- Draxler, Joar, et al.
(författare)
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A numerical model for simulating the effect of strain rate on eutectic band thickness
- 2020
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Ingår i: Welding in the World. - : Springer. - 0043-2288 .- 1878-6669. ; 64:10, s. 1635-1658
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Tidskriftsartikel (refereegranskat)abstract
- Large tensile strains acting on the solidifying weld metal can cause the formation of eutectic bands along grain boundaries. These eutectic bands can lead to severe liquation in the partially melted zone of a subsequent overlapping weld. This can increase the risk of heat-affected zone liquation cracking. In this paper, we present a solidification model for modeling eutectic bands. The model is based on solute convection in grain boundary liquid films induced by tensile strains. The proposed model was used to study the influence of strain rate on the thickness of eutectic bands in Alloy 718. It was found that when the magnitude of the strain rate is 10 times larger than that of the solidification rate, the calculated eutectic band thickness is about 200 to 500% larger (depending on the solidification rate) as compared to when the strain rate is zero. In the paper, we also discuss how eutectic bands may form from hot cracks.
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| 3. |
- Singh, Sukhdeep, 1988, et al.
(författare)
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Heat-Affected-Zone Liquation Cracking in Welded Cast Haynes® 282®
- 2020
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Ingår i: Metals. - : MDPI AG. - 2075-4701. ; 10:1
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Tidskriftsartikel (refereegranskat)abstract
- Varestraint weldability testing and Gleeble thermomechanical simulation of the newly developed cast form of Haynes® 282® were performed to understand how heat-affected-zone (HAZ) liquation cracking is influenced by different preweld heat treatments. In contrast to common understanding, cracking susceptibility did not improve with a higher degree of homogenization achieved at a higher heat-treatment temperature. Heat treatments with a 4 h dwell time at 1120 °C and 1160 °C exhibited low cracking sensitivity, whereas by increasing the temperature to 1190 °C, the cracking was exacerbated. Nanosecond ion mass spectrometry analysis was done to characterize B segregation at grain boundaries that the 1190 °C heat treatment indicated to be liberated from the dissolution of C–B rich precipitates.
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| 4. |
- Singh, Sukhdeep, 1988, et al.
(författare)
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Hot cracking in cast alloy 718
- 2018
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Ingår i: Science and Technology of Welding and Joining. - : Informa UK Limited. - 1743-2936 .- 1362-1718. ; 23:7, s. 568-574
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Tidskriftsartikel (refereegranskat)abstract
- Hot cracking susceptibility of the Fe–Ni-based precipitation hardening cast superalloy Alloy 718 was studied by Varestraint weldability testing. The effect of two hot isostatic pressing (HIP) treatments commonly employed in the aerospace industry was investigated in reference to the as cast condition. It was found that the heat affected zone (HAZ) liquation cracking susceptibility increased for samples with pre-weld HIP treatments. The as cast condition disclosed the best response for liquation cracking followed by HIP-1120 (1120°C/4h (HIP) + 1050°C/1h and furnace cooling to 650°C/1h in vacuum + 950°C/1h) and HIP-1190 (1190°C/4h (HIP) + 870°C/10h and furnace cooling to 650°C/1h in vacuum + 950°C/1h). The amount of the secondary precipitates and base metal grain size was found to be important parameters influencing the cracking susceptibility. Regarding solidification cracking susceptibility, the three conditions appear to behave similarly.
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| 5. |
- Singh, Sukhdeep, 1988, et al.
(författare)
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Influence of Hot Isostatic Pressing on the Hot Ductility of Cast Alloy 718 : The Effect of Niobium and Minor Elements on the Liquation Mechanism
- 2020
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Ingår i: Metallurgical and Materials Transactions. A. - : Springer. - 1073-5623 .- 1543-1940. ; 51:12, s. 6248-6257
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Tidskriftsartikel (refereegranskat)abstract
- The influence of two hot isostatic pressing (HIP) treatments on liquation behavior was investigated and compared with regard to the extent of heat-affected zone liquation cracking in cast Alloy 718. The extent of liquation was seen to increase after HIP treatment at 1190 °C due to solute changes caused by the homogenization of Nb, which contributed to extensive grain boundary melting. The HIP treatment at 1120 °C exhibited lower liquation with contributions from particle liquation of the Laves phase and constitutional liquation of NbC carbides. This was also reflected in a lower ductility recovery temperature, with slower recovery for the former due to the extensive liquation. Interestingly, the nil ductility temperatures were both below the predicted equilibrium solidus of the alloy, which suggests that the ductility drop is related to liquation caused by solute segregation at the grain boundaries. © 2020, The Author(s).
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| 6. |
- Singh, Sukhdeep, 1988, et al.
(författare)
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Investigation on effect of welding parameters on solidification cracking of austenitic stainless steel 314
- 2018
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Ingår i: Procedia Manufacturing. - : Elsevier BV. - 2351-9789. ; , s. 351-357
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- This study investigates the solidification cracking susceptibility of the austenitic stainless steel 314. Longitudinal Varestraint testing was used with three different set of welding test parameters. Weld speed, current and voltage values were selected so that the same heat input resulted in all the test conditions. From the crack measurements it was seen that the test condition with the lowest current and welding speed value also produced the least amount of cracking with very good repeatability.
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| 7. |
- Singh, Sukhdeep, 1988, et al.
(författare)
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Varestraint Weldability Testing of ATI 718Plus® : Influence of Eta Phase
- 2018
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Ingår i: Proceedings of the 9th International Symposium on Superalloy 718 & Derivatives. - Cham : Springer. - 9783319894799 - 9783319894805 ; , s. 929-937, s. 929-937
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Konferensbidrag (refereegranskat)abstract
- This study investigates the effect of eta phase on hot cracking susceptibility of ATI 718Plus®. Two heat treatment conditions of 950 °C/1 h and 950 °C/15 h having different amounts of eta phase were tested by longitudinal Varestraint testing method. The heat treatment at 950 °C/15 h exhibited the highest amount of cracking. This was related to the higher amount of eta phase precipitation during the long dwell heat treatment which aided to extensive liquation during welding.
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| 8. |
- Singh, Sukhdeep, 1988, et al.
(författare)
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Varestraint weldability testing of cast ATI® 718Plus™ : a comparison to cast Alloy 718
- 2019
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Ingår i: Welding in the World. - : Springer Science and Business Media LLC. - 0043-2288 .- 1878-6669. ; 63:2, s. 389-399
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Tidskriftsartikel (refereegranskat)abstract
- Varestraint testing of the newly developed cast ATI® 718Plus™ after pseudo-HIP (hot isostatic pressing) heat treatments showed that the extent of solidification cracking was independent of the heat treatment condition. The susceptibility towards heat-affected zone (HAZ) liquation cracking was found to be related to the heat treatment dwell time rather than the temperature. The heat treatments at 1120 and 1190Â °C for 24 h were the most susceptible to cracking. On the other hand, heat treatments at 1120, 1160 and 1190 °C for 4-h dwell time exhibited the least amount of cracking. The solidification cracking was found to be similar whereas the HAZ liquation cracking was lower for ATI® 718Plus™ after the heat treatment at 1120 and 1190 °C for 4-h dwell time in comparison to cast Alloy 718.
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| 9. |
- Singh, Sukhdeep, 1988
(författare)
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Varestraint Weldability Testing of Cast Superalloys
- 2018
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Precipitation hardened Ni- and Ni-Fe- based superalloys, used in hot structural components for aero engines, are subjected to hot cracking phenomena during manufacturing and specifically in welding. This type of cracking involves metallurgical reactions from the liquid phase in concomitance to weld restraints. Hot cracking is more pronounced during the welding of cast superalloys compared to its wrought counterparts owing to the larger inhomogeneity in the cast material. Cast structural components must therefore undergo a hot isostatic pressing (HIP) treatment prior to welding for closing any pores from the casting process and homogenizing the material. The current study is about the effect of two HIP treatments commonly employed in the aerospace industry on the weldability of the cast Alloy 718. Moreover, the weldability of the recently introduced cast version of ATI® 718PlusTM is also addressed, including the assessment of five different pseudo-HIP treatments and the weldability of the two cast superalloys is compared. Testing was conducted using the Varestraint (Variable-Restraint) weldability testing technique, where test plates were welded by a robot and at the same time bended to achieve external restraint. Welding and test parameters were the same for all the conditions. The hot cracking susceptibility of cast Alloy 718 was found to be worse with increasing HIP treatment temperature. It was found that HIP treatment conducted at 1190°C/4h gave higher crack susceptibility than the one at 1120°C/4h. Cast ATI® 718PlusTM was heat treated using short dwell heat treatments for 4h at 1120°C, 1160°C and 1190°C and long dwell heat treatments for 24h at both 1120°C and 1190°C, respectively. The cracking susceptibility was found to be related to the heat treatment dwell time rather than the temperature. The heat treatment at 4h dwell time exhibited lower amount of cracking than the 24h dwell heat treatment. Considering the comparative heat treatments at 1120°C/4h and 1190°C/4h, the new cast superalloy ATI® 718PlusTM was found to have lower cracking susceptibility than the cast Alloy 718.
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| 10. |
- Singh, Sukhdeep, 1988
(författare)
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Weldability of Cast Superalloys - Effect of homogenization heat treatments on hot cracking susceptibility of cast Alloy 718, ATI® 718Plus®, and Haynes® 282®
- 2020
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Precipitation hardened Ni- and Ni–Fe-based superalloys are used in high-temperature sections of aero engines owing to their superior mechanical properties compared to those of the other alloys. However, their better mechanical performance is accompanied by its own challenges during the manufacturing process. For the fabrication of hot structural components, instead of the traditional single piece castings, welding is widely employed by joining wrought parts in sections, where high strength is required, and cast parts, where complex geometrical shapes are needed. This can be challenging, as superalloys are known for their lack of amenability to welding. A weld-cracking phenomenon known as “hot cracking”is of concern during their welding. Especially, the cast materials are known to be more prone to cracking owing to the higher extent of segregating phases that remain from the casting process.The present study investigates the weldability of Alloy 718 and two recently developed Ni-based superalloys ATI® 718Plus® and Haynes® 282® with respect to heat affected zone liquation (HAZ) cracking susceptibility. Pre-weld homogenization treatments were performed at 1120 °C and 1190 °C to study the effect of different microstructures on cracking extent. The testing approach consisted of using Varestraint weldability test to assess the HAZ liquation cracking susceptibility and Gleeble thermomechanical simulator for evaluation of hot ductility behaviour. The results revealed that a lower heat treatment temperature at 1120 °C for 4 h was beneficial in minimizing the influence of liquation, and that the grain growth also contributed to lowering the cracking susceptibility in the HAZ. JMatPro simulations and microstructural evaluation on elements such as Nb as solute and precipitate former in Alloy 718 and ATI® 718Plus®, and Mo in Haynes® 282® were found to be important in the liquation mechanism. Secondary ion mass spectroscopy (SIMS) analysis revealed B, which is a strong melting point depressant, to segregate along the grain boundaries in all the three alloys. In addition, in this thesis, different liquation mechanisms were discussed and an explanation for the overall HAZ liquation cracking mechanism for cast superalloys was proposed.
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