Microstructural Stability and Creep Performance of a Novel Low-Cost Single Crystal Superalloy

The increasing pursuit of advanced aero-engines with lower ratio between the cost and performance has greatly promoted the demanding of single crystal superalloys characterized by low cost and outstanding temperature capability. In this study, a novel low-cost single crystal superalloy was designed and the creep tests as well as micro-characterization were carried out on the experimental alloy. The results illustrated that the novel single crystal alloy exhibited an ideal microstructural stability without precipitating TCP phases, after long-term thermal exposure at the ultimate service temperature of third generation single crystal superalloys. Moreover, the experimental alloy with only 3 wt% Re addition demonstrated remarkable creep resistance and maintained a very low minimum creep rate at 1100 °C/137 MPa and 1120 °C/137 MPa, while the accumulation and coalescence of micro-pores had eventually led to the alloy fracture. Apart from that, the compact interfacial dislocation networks the 2nd γ′ phase were observed after high-temperature creep rupture, and the typical a   superdislocations with relatively poor mobility was found at 1120 °C. At 760 °C/800 MPa, both the minimum creep velocity and entire creep stain was increased evidently, however, the ultimate creep rupture life of the alloy had still reached 200 h. The corresponding deformation mechanism was identified as the combination of superdislocation pairs shearing and a/3   partial dislocation cutting the γ′ phase with a SISF being generated. In general, the novel single crystal alloy characterized by remarkable mechanical properties and cost reduction possesses a great potential for future application in the advanced aircraft engines. At high temperature and low stress creep condition, the compact interfacial dislocation networks the 2nd γ′ phases were observed, and the rafted γ′ phase were ultimately sheared by both a and a superdislocation pairs. At medium temperature and high stress condition, the combined deformation mechanisms of superdislocation pairs shearing and a/3 partial dislocation cutting the γ′ phase with a SISF being generated were identified.