The influences of elevated Co and Ti levels on the mechanical properties of the Ni-base superalloy RR1000 have been investigated. Following heat treatment, the modified alloys had the typical γ–γ′ microstructure, with γ′ precipitate sizes comparable to similarly heat treated RR1000, but with a slightly higher volume fraction. The modified alloys exhibited a higher proof stress than RR1000 across the entire 20 to 800°C temperature range investigated. Superior creep rupture lives, when compared to RR1000, were observed in the modified alloys at 700°C, but not at 750°C, where extensive precipitation of topologically close packed σ phase occurred on the grain surfaces. The formation of this deleterious phase was linked to Cr and Mo enrichment of the γ matrix, caused by the elevated Co and Ti additions.
‘European aeronautics: A vision for 2020’, European Commission, 2001.
2.
‘Flightpath 2050: Europe's vision for aviation’, European Commisson, 2011.
3.
DeckerRF: ‘Strengthening mechanisms in nickel-base superalloys’, in ‘Steel strengthening mechanisms’, 147–170; 1969, Greenwich, CT, Climax Molybdenum Co.
4.
GibbonsTB and HopkinsBE: ‘Creep behaviour and microstructure of Ni-Cr base alloys’, Met. Sci., 1984, 18, (5), 273–280.
5.
ManiarGN and BridgeJE: ‘Effect of gamma-gamma prime mismatch, volume fraction gamma prime, and gamma prime morphology on elevated temperature properties of Ni, 20 Cr, 5·5 Mo, Ti, Al alloys’, Metall. Trans., 1971, 2, (1), 95–102.
6.
RaynorD and SilcockJM: ‘Strengthening mechanisms in γ′ precipitating alloys’, Met. Sci., 1970, 4, (1), 121–130.
7.
FountainRW and ForgengWD: ‘Phase relations and precipitation in Cobalt-Titanium alloys’, Trans. Metall. Soc. AIME, 1959, 215, 998–1008.
8.
BirbringH and ManencJ: ‘Structure des phases dans le système Co-Ti’, Comptes rendus hebdomadaires des séances de l'Académie des Sciences, 1959, 249, 1508–1510.
9.
ViatourP, DrapierJM and CoutsouradisD: ‘Stability of the gamma prime Co3Ti compound in simple and complex cobalt alloys’, Cobalt, 1972, 3, 67–74.
10.
BlaiseJM, ViatourP and DrapierJM: ‘On the stability and precipitation of the Co3Ti phase in Co-Ti alloys’, Cobalt, 1970, 49, 192–195.
11.
ViatourP, DrapierJM, CoutsouradisD and HabrakenL: ‘Structure and properties of CM-7 a wrought precipitation-hardening cobalt-base alloy’, Cobalt, 1971, 51, 67–76.
12.
CuiCY, GuYF, PingDH and HaradaH: ‘Phase constituents in Ni–Al–Co–Ti quaternary alloys’, Intermetallics, 2008, 16, (7), 910–916.
13.
CuiC, GuY, HaradaH and SatoA: ‘Microstructure and yield strength of UDIMET 720LI alloyed with Co-16·9 Wt Pct Ti’, Metall. Mater. Trans. A, 2005, 36A, (11), 2921–2927.
14.
GuY, HaradaH, CuiC, PingD, SatoA and FujiokaJ: ‘New Ni–Co-base disk superalloys with higher strength and creep resistance’, Scr. Mater., 2006, 55, (9), 815–818.
15.
CuiCY, GuYF, PingDH, HaradaH and FukudaT: ‘The evolution of η phase in Ni–Co base superalloys’, Mater. Sci. Eng. A, 2008, A485, (1–2), 651–656.
16.
CuiCY, GuYF, PingDH, FukudaT and HaradaH: ‘Phase constituents and compressive yield stress of Ni-Co base alloys’, Mater. Trans., 2008, 49, (3), 424–427.
17.
CuiCY, GuYF, PingDH and HaradaH: ‘Microstructural evolution and mechanical properties of a Ni-based superalloy, TMW-4’, Metall. Mater. Trans. A, 2009, 40A, (2), 282–291.
18.
CuiCY, GuYF, HaradaH, PingDH and SatoA: ‘Phase stability and yield stress of Ni-base superalloys containing high Co and Ti’, Metall. Mater. Trans. A, 2006, 37A, (11), 3183–3190.
19.
MitchellRJ: ‘Development of a new powder processed Ni-base superalloy for rotor disc application’, PhD thesis, University of Cambridge, UK, 2004.
20.
BoettingerWJ, KattnerUR, MoonK.-W and PerepezkoJH: ‘DTA and heat-flux DSC measurements of alloy melting and freezing’, 960-15, NIST, 2006.
21.
MinshullJ: ‘A1-L12 alloys based on the Al-Co-Ni-Ti quaternary system’, PhD thesis, University of Cambridge, UK, 2010.
22.
ConnorLD: ‘The development of a dual microstructure heat treated Ni-base superalloy for turbine disc applications’, PhD thesis, University of Cambridge, UK, 2009.
23.
CollinsDM, YanL, MarquisEA, ConnorLD, CiardielloJJ, EvansAD and StoneHJ: ‘Lattice misfit during ageing of a polycrystalline nickel-base superalloy’, Acta Mater., 2013, 61, (20), 7791–7804.
24.
NathalMV, MaierRD and EbertLJ: ‘The influence of cobalt on the tensile and stress-rupture properties of the nickel-base superalloy mar-m247’ MAR-M247, Metall. Trans. A, 1982, 13A, (10), 1767–1774.
25.
KozarRW, SuzukiA, MilliganWW, SchirraJJ, SavageMF and PollockTM: ‘Strengthening mechanisms in polycrystalline multimodal nickel-base superalloys’, Metall. Mater. Trans. A, 2009, 40A, (7), 1588–1603.
26.
JacksonMP and ReedRC: ‘Heat treatment of UDIMET 720Li: the effect of microstructure on properties’, Mater. Sci. Eng. A, 1999, 259A, (1), 85–97.
27.
MiodownikA and SaundersN: in ‘Application of thermodynamics in the synthesis and processing of materials’, (ed. NashPet al.), 91–104; 1995, Warrendale, PA, The Minerals, Metals and Materials Society.
28.
BraggW and WilliamsE: ‘The effect of thermal agitation on atomic arrangement in alloys’, Proc. R. Soc. A, 1934, 145A, 699–730.
29.
GeroldV and HaberkornH: ‘On the critical resolved shear stress of solid solutions containing coherent precipitates’, Phys. Status Solidi, 1966, 16, (2), 675–684.
30.
ParkerBA: ‘On the contribution of coherence to the strength of nickel-aluminium-titanium alloys’, Scr. Metall., 1970, 4, (11), 905–906.
31.
GroseDA and AnsellGS: ‘The influence of coherency strain on the elevated temperature tensile behavior of Ni-15Cr-AI-Ti-Mo alloys’, Metall. Trans. A, 1981, 12A, (9), 1631–1645.
32.
ParkerBA: ‘On the contribution of coherency strains to the strength of alloys’, Mater. Sci. Forum, 1995, 189–190, 347–352.
33.
MunjalV and ArdellAJ: ‘Precipitation hardening of Ni-12·19 at.% Al alloy single crystals’, Acta Metall., 1975, 23, (4), 513–520.
34.
NembachE and NeiteG: ‘Precipitation hardening of superalloys by ordered γ′-particles’, Prog. Mater. Sci., 1985, 29, (3), 177–319.
35.
SchänzerS and NembachE: ‘The critical resolved shear stress of γ′-strengthened nickel-based superalloys with γ′-volume fractions between 0·07 and 0·47’, Acta Metall. Mater., 1992, 40, (4), 803–813.
36.
MelanderA and PerssonPA: ‘Strength of γ′ hardened nickel-base alloy’, Met. Sci., 1978, 12, (9), 391–398.
37.
YuanY, GuY, CuiC, OsadaT, ZhongZ, TetsuiT, YokokawaT and HaradaH: ‘Influence of Co content on stacking fault energy in Ni-Co base disk superalloys’, J. Mater. Res., 2011, 26, (22), 2833–2837.
38.
ReedRC, JacksonMP and NaYS: ‘Characterization and modeling of the precipitation of the sigma phase in UDIMET 720 and UDIMET 720LI’, Metall. Mater. Trans. A, 1999, 30A, (3), 521–533.
39.
RaeCMF and ReedRC: ‘The precipitation of topologically close-packed phases in rhenium-containing superalloys’, Acta Mater., 2001, 49, (19), 4113–4125.
40.
WangWZ, JinT, LiuJL, SunXF, GuanHR and HuZQ: ‘Role of Re and Co on microstructures and γ′ coarsening in single crystal superalloys’, Mater. Sci. Eng. A, 2008, 479A, (1–2), 148–156.
41.
LundCH, WouldsMJ and HockinJ: ‘Cobalt and sigma: Participant, spectator, or referee?’, Proc. Int. Symp. on ‘Structural stability in superalloys’, Seven Springs, PA, USA, September 1968, AIME, 25–46.
