An investigation was conducted to determine the mechanisms of failure of turbine blades of Hastelloy B, a forged nickel-base alloy, and Stellite 21, a precision-cast cobalt-base alloy, when operated in a J33-9 turbojet engine. The blades were alternately spaced in a 16-25-6 alloy rotor and subjected to simulated service operation con¬sisting of 20-minute cycles (15 min at rated speed and approximately 5 min at idle). The engine conditions at rated speed were 11,500 rpm and a gas temperature of 1250° F at the exhaust-cone outlet. For these operating conditions, the estimated maximum blade temperature in the normal zone of failure was 1500° F and the centrifugal stress in this zone was 25,000 pounds per square inch for the Hastelloy B and 21,000 pounds per square inch for the Stellite 21 blades.
展开▼
