1.
Andersson, Joel Håkan, 1981, et al.
(author)
Investigation of Homogenization and its Influence on the Repair Welding of Cast Allvac 718Plus
2010
In: Proceedings of The 7th International Symposium on Superalloy 718 and Derivatives, TMS (The Minerals, Metals and Materials Society). - Hoboken, NJ, USA : John Wiley & Sons, Inc.. - 9781617827709 ; , s. 439-454, s. 439-454
Conference paper (peer-reviewed) abstract
Heat treatment experiments have been carried out to bring understanding to the efficacy of different temperatures and dwell times on the degree of homogenization of the cast Allvac 718Plus alloy which is prone to segregation mainly due to its high content of niobium. The effect of homogenization on weld repair was also examined. The homogenization heat treatment temperatures ranged from 1050°C to 1200°C with 1hr, 5 hrs and 10 hrs dwell times. The degree of homogenization was measured as the reduction of the amount of Laves phase by manual point counting in an optical microscope at high magnification. Longer range, interdendritic, patterns were established through line scan EDS analysis in SEM. It was found that short time (1hr) does not significantly reduce the amount of Laves phase whereas 5 hrs and 10hrs are much more efficient. Interdendritic homogenization does not occur to any measurable extent even at the highest temperature and longest dwell time (1200°C-10hrs) which was also reflected in bulk macro Vickers hardness tests.In the weld repair tests, one of the most homogenized material conditions (1125°C-5hrs +1200°C-10hrs) turned out to be the most prone to cracking while the number of weld cracks after a moderate homogenization heat treatment (1125°C-5hrs) was much smaller .
2.
Andersson, Joel, 1981-, et al.
(author)
Hot Ductility Study of Haynes 282 Superalloy
2010
In: Superalloy 718 and Derivatives. - Hoboken, NJ, USA : The Minerals, Metals, and Materials Society. - 9780470943168 ; , s. 539-554, s. 539-554
Conference paper (peer-reviewed)
3.
Andersson, Joel, 1981-, et al.
(author)
Metallurgical Response of Electron Beam Welded Allvac® 718Plus™
2011
In: Hot Cracking Phenomena in Welds III. - Berlin, Heidelberg : Springer Berlin/Heidelberg. - 9783642168635 ; , s. 415-428, s. 415-428
Conference paper (peer-reviewed) abstract
Electron beam welding of forged Allvac 718Plus superalloy has been carried out without any visible cracks in weld cross-sections. Healed cracks in the heat affected zone were, however, seen in most cross-sections with the healing as well as the cracking believed to be due to the constitutional liquation of the δ-phase. The δ-phase undergoes constitutional liquation in the Heat Affected Zone (HAZ) and consequently decreases the ductility of the material and renders cracks in the HAZ but due to the large amount of eutectic liquid produced at the same time the healing of the opened cracks takes place.
4.
Andersson, Joel, 1981-, et al.
(author)
Effect of Different Solution Heat Treatments on the Hot Ductility of Superalloys : Part 3 - Waspaloy
2013
In: Materials Science and Technology. - 0267-0836 .- 1743-2847. ; 29:1, s. 43-53
Journal article (peer-reviewed) abstract
The susceptibility to heat affected zone cracking of Waspaloy has been investigated in terms of its hot ductility, measured as the reduction of area (RA). Gleeble testing with on-heating as well as on-cooling test cycles was carried out to illuminate the influence of different 4 h solution heat treatments between 996 and 1080°C. A ductility maximum of between 80 and 90%RA was found at 1050–1100°C for all conditions in the on-heating tests. Although the different heat treatment conditions showed similar macrohardness, the particle size and distribution of the γ′ and M23C6 phases differed, which significantly affected the on-heating ductility in the lower temperature test region. The ductile to brittle transition was initiated at 1100°C in the on-heating testing with indications of grain boundary liquation at the higher test temperatures. Ductility recovery, as measured in the on-cooling tests from 1240°C, was very limited with <30%RA for all conditions and test temperatures except for the 1080°C/4 h treatment, which exhibited 60%RA at 980°C.
5.
Andersson, Joel Håkan, 1981, et al.
(author)
Effect of different solution heat treatments on hot ductility of superalloys Part 2-Allvac 718Plus
2012
In: Materials Science and Technology. - : Taylor & Francis Group. - 1743-2847 .- 0267-0836. ; 28:6, s. 733-741
Journal article (peer-reviewed) abstract
The hot ductility of Allvac 718Plus for different solution heat treatments (954 degrees C-15 h, 954 degrees C-1 h, 982 degrees C-1 h and 1050 degrees C-3 h+954 degrees C-1 h) has been investigated using Gleeble testing. Substantial variations in the microstructure among the heat treatments affected the Gleeble test hot ductility only to a very limited extent. Constitutional liquation of the NbC phase was found to be the main cause for the poor ductility at high testing temperatures in the on-heating cycle as well as at the lower temperatures on-cooling. Grain boundary delta phase was seen to assist the constitutional liquation of the NbC phase. Based on established evaluation criteria for Gleeble ductility testing, a ranked indicator for weldability is suggested.
6.
Andersson, Joel Håkan, 1981, et al.
(author)
Repair welding of wrought superalloys: Alloy 718, Allvac 718Plus and Waspaloy
2012
In: Science and Technology of Welding and Joining. - 1743-2936 .- 1362-1718. ; 17:1, s. 49-59
Journal article (peer-reviewed) abstract
The ability to weld repair three precipitation hardening superalloys, Alloy 718, Allvac 718Plus and Waspaloy, with GasTungsten Arc Welding is compared in this study. Four different solution heat treatment conditions for each material were examined; Alloy 718 and Allvac 718Plus heat treated at 954 °C-1 h, 982 °C-1 h, 954 °C-15 h and 1020 °C-1 h and Waspaloy for 4 h at 996 °C, 1010 °C, 1040 °C and at 1080 . By metallography, the total number of cracks was evaluated both in the HAZ and in the FZ which made it possible to consistently rate the repair weldability of these three materials. Alloy 718 was significantly the best one with Allvac 718Plus slightly better than Waspaloy. As expected, the solution heat treatment conditions only affected the HAZ cracking behavior.
7.
Cedergren, Stefan, 1982, et al.
(author)
On the Influence of Work Material Microstructure on Chip Formation, Cutting Forces and Acoustic Emission when Machining Ti-6Al-4V
2013
In: Procedia CIRP. - : Elsevier BV. - 2212-8271. ; 12, s. 55-60
Conference paper (peer-reviewed) abstract
The influence of heat treatment of work material on chip formation, when machining Ti-6Al-4V, was studied through microstructural investigation of chips, as well as response on cutting forces and acoustic emission. Three different microstructures were investigated; equiaxed, bimodal and Widmanstätten. It is well known that machining of titanium produces shear localized chips at all industrially practical cutting speeds and feed rates, however there is also a transition from aperiodic to periodic sawtooth chip formation. The feed rate was varied at constant cutting speed to study this transition from aperiodic to periodic saw-tooth chips in the three microstructures. Face turning cutting tests were used when sensor signals were collected. The results from this investigation stress the importance to consider work material microstructure when studying the chip formation process, and its impact on cutting forces and acoustic emission, when machining Ti-6Al-4V.
8.
Cedergren, Stefan, 1982, et al.
(author)
The effects of grain size and feed rate on notch wear and burr formation in wrought Alloy 718
2013
In: International Journal of Advanced Manufacturing Technology. - : Springer Science and Business Media LLC. - 0268-3768 .- 1433-3015. ; 67:5-8, s. 1501-1507
Journal article (peer-reviewed) abstract
The effect of two different workpiece material grain sizes, 16 and 127 μm, on the depth-of-cut notch wear, chip morphology, and burr formation was studied in a turning operation. A material from the same batch of wrought superalloy Alloy 718 was heat-treated to achieve the two microstructures. The machining was performed at two feed rates, 0.1 and 0.2 mm/revolution. Uncoated cemented carbide tools were used. Both grain size and feed rate were found to influence the chip morphology and the sideflow which were also associated with both the notch wear and the burr formation. The effect of the grain size on the notch wear was larger than that of the feed rate under the tested conditions, with larger grains being more detrimental than smaller ones.
