Crack Analysis of Compressor Drum Seal Teeth of TC17 Titanium Alloy

An engine was sent back to factory for repairing after its second service time limit. Crack was macroscopically visible in three seal teeth between drum and frist- and second-grade discs during florescence detection on the high-pressure compressor of TC17 titanium alloy. In order to find out the failure cause, the distribution, morphology and direction of the crack were observed, the crack fracture was analyzed, and the degree of wear and burn of 4 seal teeth along the circumference of the connecting drum was inspected. The results show that the cracking mode is fatigue cracking. The reason for the fatigue crack is that the designed clearance between seal teeth and honeycomb ring is too small, so a great deal of heat was emitted because of severely grinding while the engine worked. The thermal conductivity of titanium alloy is low, so the heat could not be transmitted in time, resulting in the overheating and even overburning of teeth top as well as the weakening of their properties. The fatigue crack initiated and propagated due to the grinding stress of high-speed rotation of engine. Such a problem can be solved by widening the designed clearance between seal teeth and honeycomb ring, improving the manufacturing technique and lowering the hardness of honeycomb ring.