Stress rupture behaviour of the single crystal superalloy NASAIR 100 at 1050°C

The microstructure and elevated temperature stress rupture behaviour of NASAIR 100 single crystals were investigated under both as-grown and heat treated conditions. The γ + ′ in the as-grown microstructure was smaller than that in heat treated microstructure. Additionally, some W-rich plates were present after solution heat treatments. Superior stress rupture properties were gained after heat treatment at 1320 °C/4 hours A/C. Creep cracks initiated not only at micropores, but also at γ/γ + ′ eutectic, W-rich plates and even γ/γ + ′ interfaces. Once cracks formed, they propagated until tearing ridges joined them with each other. At last, fracture took place at a much higher stress.