Temperature dependence of the dynamic fracture toughness and the specific impact energies of the alloy Nimonic 86 in the temperature range 293 < T/K < 1223

Precracked Charpy V-notch specimens of the nickel base alloy Nimonic 86 in the as-received condition have been tested using an instrumented impact tester (hammer) in the temperature range 293 < T/K < 1223. The specific impact energies were determined by dial readings from the maximum angle of the afterswing after the impact, from the integration of the load versus time and the load versus load point displacement diagrams; in all cases the agreement was excellent. The specific impact energy and the impulse are correlated with the test temperature. The dynamic fracture toughness values were determined following the equivalent energy approach. While the temperature dependency of the specific impact energies and the impulses reveal a distinct maximum at T = 773 K (500 degrees C) no such maximum in the temperature dependence of the dynamic fracture toughness was observed. The fracture surfaces show distinct elasto-plastic fracture behaviour of the material in the temperature regime investigated. (author)