Superior creep resistance in a γ′-strengthened Co-based single-crystal superalloy at 760°C and ∼90% yield strength

Figures & data

Figure 1. Comparison of creep curves between the alloy TaTi and a Re-containing CMSX-4 type alloy (ERBO/1-3Re) [5] at ∼760°C/800 MPa. (a) Creep strain vs. time; (b) creep rate vs. creep strain.

Figure 2. SEM images showing the typical γ/γ′ microstructures of alloy TaTi at 760°C/800 MPa with different creep times and strains. (a) horizontal sections; (b) longitudinal sections; (1) ε = ∼1.0%, t = ∼160 h; (2) ε = ∼5%, t = ∼608 h; (3)ε = ∼11%, t = ∼854 h.

Table 1. Evolution of the volume fraction (V_γ′), area equivalent diameter (d_γ′)/raft thickness (D_γ′) of γ′ phase and the width of γ channel (D_γ) during the creep at 760°C/800 MPa in alloy TaTi.

T	∼8h	∼93h	∼160h	∼608h	∼854h
ε	∼0.06%	∼0.2%	∼1%	∼5%	∼11%
Vγ′/%	81.8 ± 1.6	80.5 ± 2.5	80.7 ± 1.5	79.7 ± 1.7	79.5 ± 1.9
dγ′/nm	190 ± 44	203 ± 45	210 ± 33	–	–
Dγ′/nm	–	–	–	214 ± 23	–
Dγ/nm	19 ± 6	18 ± 10	24 ± 8	29 ± 9	–

Figure 3. STEM images showing the typical deformation substructures of alloy TaTi at 760°C/800 MPa in different creep stages, B = [100]. (a) decelerating creep stage, ε = ∼0.06%; (b) accelerating creep stage, ε = ∼0.2%; slow accelerating creep stage at (c) ε = ∼1% and (d) ε = ∼5%.

Figure 4. HAADF-STEM image and corresponding EDX elemental mapping (at.%) of a SISF at 760°C/800 MPa with ε = ∼1% (t = ∼160 h), B = [110].

Figure 5. Schematic diagram of the interactions between γ/γ′ microstructures and deformation substructures in different creep stages of (a) ERBO/1-3Re [5] and (b) alloy TaTi at low temperature/high stress. (1) accelerating, (2) middle and (3) late stages of the creep process.

Table 2. Creep properties of various single-crystal superalloys at ∼760 °C/high stress (80%∼90% yield strength) [5,23,34].

Alloy	Time for ε = 1%(h)	Rupture life (h)	Rupture strain(%)	Primary creep strain /Time(%/h)	Primary creep rate(10^−6 s^−1)	Minimum creep rate(10^−7 s^−1)
Alloy TaTi	∼250	∼854	∼11	<0.15/<1	-	∼0.03
AM1 [23]	∼30	∼165	∼12	∼0.25/<1	-	∼0.6
ERBO/1-3Re [5]	∼1	∼530	∼14	∼2.5/∼6	∼2.4	∼0.2
Alloy-4Re [34]	∼5	∼620	∼24	∼6.5/∼10	∼3.2	∼0.3
MC544-4Re4Ru [23]	∼1	∼143	∼27	∼5.9/∼10	∼6.3	∼2.2

Table 3. Evolution of substructures in γ′ phase of different SX superalloys during the critical creep stages at low temperature/high stress [5,28].

Alloy	Accelerating creep stage	Middle creep stage	Late creep stage
ERBO/1-3Re [5,28]	a < 112> SF ribbons	SF interactions	Dislocation pairs
Alloy TaTi	Individual SFs	SF interactions	SF interactions

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Data availability

The raw/processed data required to reproduce these findings cannot be shared at this time as the data also forms part of other ongoing studies.