Recent advances in the development of aerospace materials

Ab-initio investigation of structure and mechanical properties of PtAlTM ternary alloy

Hierarchical crystal plasticity FE model for nickel-based superalloys: Sub-grain microstructures to polycrystalline aggregates

The hydrogenation mechanism of PtAl and IrAl thermal barrier coatings from first-principles investigations

Creep behavior of a single crystal nickel-based superalloy containing 4.2% Re

The influence of microstructure and orientation on creep and rupture behavior of DMS4-type nickel-based superalloy single crystal rods has been studied While microstructures have been examined by optical, scanning and transmission electron microscopy, compositions and orientations have been studied by electron microprobe analyzer and electron backscattered diffraction, respectively Creep experiments carried out on near-〈0 0 1〉 oriented specimens at stress and temperature ranges of 90–450 MPa and 870–1110 °C, respectively have shown similar strains for specific fraction of rupture life irrespective of stress, rupture strengths superior to or comparable with that of commercial single crystal alloys, and rafting of γ ′ precipitates perpendicular to loading direction with average raft thickness decreasing with stress Rupture-life and creep-ductility for near-〈0 1 1〉 oriented specimens are found to be lower than that for near-〈0 0 1〉 orientations, due to formation of inclined rafts in the former specimens, which are less effective as obstacles for dislocation motion than those perpendicular to load-axis

Microstructure and creep behavior of DMS4-type nickel based superalloy single crystals with orientations near 001 and 011

The effect of cyclic oxidation exposure at 1100 °C in air on the tensile properties of directionally solidified Ni-based superalloy CM-247LC has been studied. The residual machining stresses present in the tensile samples induced the formation of a recrystallization zone at the surface during oxidation exposure. Additionally, a γ′ precipitate-free zone also formed at the surface of the tensile specimens. The tensile properties of the alloy, including YS, UTS and ductility, were greatly degraded because of the oxidation exposure. The deterioration in the properties can be ascribed to the combined effect of the above mentioned surface damages and the microstructural degradation in terms of the coarsening of primary γ′ precipitates of the substrate during the high temperature exposure.

Effect of cyclic oxidation on the tensile behavior of directionally solidified CM-247LC Ni-based superalloy at 870 °C

A method has been suggested to accurately determine the DBTT of diffusion aluminide bond coats. Micro-tensile testing of free-standing coating samples has been carried out. The DBTT was determined based on the variation of plastic strain-to-fracture with temperature. The positive features of this method over the previously reported techniques are highlighted.

Evaluation of ductile-brittle transition temperature (DBTT) of aluminide bond coats by micro-tensile test method

The effect of Pt–aluminide bond coat on the mechanical properties, namely tensile and creep, of a Ni-base single crystal superalloy has been investigated. Tensile properties of both uncoated and bond coated specimens were evaluated in the temperature range of room temperature (RT)-1100 °C. Creep testing was carried out using four combinations of temperature and stress, viz. 850 °C/500 MPa, 982 °C/240 MPa, 1038 °C/138 MPa and 1100 °C/90 MPa. By and large, the presence of bond coat reduced the tensile strength of the superalloy at all temperatures. However, the coated alloy exhibited a higher ductility than the uncoated alloy in the above temperature range. The lowering of strength in the coated alloy can be explained in terms of the significantly lower strength of the coating as compared to that of the substrate, which caused a decrease in the strength of the coating-substrate composite structure. The higher ductility of the coated alloy, especially at elevated temperatures, can be attributed to the surface protection provided by the oxidation resistant bond coat to the substrate. The creep properties (strain-to-fracture and creep life) of the coated alloy were somewhat inferior to those of the uncoated alloy at all test temperatures. This can be ascribed to the low strength of the bond coat at high temperatures and also to the microstructural changes that took place in and near the coating during the creep test.

Effect of Pt–aluminide bond coat on tensile and creep behavior of a nickel-base single crystal superalloy

The effect of cyclic oxidation on the tensile creep properties of a Pt-aluminide (PtAl) coated directionally solidified Ni-based superalloy (CM-247LC) has been evaluated at 980 °C/220 MPa. Cyclic oxidation of creep specimens was carried out at 1100 °C in air up to 750 h. Creep rate and creep life were found to be adversely affected by thermal exposure/oxidation. The extent of degradation of these properties increased with increase in the duration of thermal exposure/oxidation. Such creep behavior has been correlated with the microstructural changes taking place in the coating such as formation of γ′ films/envelopes at B2 (NiAl) grain boundaries, formation of parallel rafts in the region close to coating–substrate interface and coarsening of γ′ precipitates in the substrate superalloy during oxidation. The creep strain, on the other hand, was not significantly affected by oxidation. This can be attributed to the prevention of oxidation induced damage by the presence of the coating.

D. Chatterjee

Papers

Microstructure and creep behavior of DMS4-type nickel based superalloy single crystals with orientations near 001 and 011

Effect of cyclic oxidation on the tensile behavior of directionally solidified CM-247LC Ni-based superalloy at 870 °C

Evaluation of ductile-brittle transition temperature (DBTT) of aluminide bond coats by micro-tensile test method

Effect of Pt–aluminide bond coat on tensile and creep behavior of a nickel-base single crystal superalloy

Creep behavior of Pt-aluminide (PtAl) coated directionally solidified Ni-based superalloy CM-247LC after thermal exposure