Rafting of Single Crystal Superalloy by High Thermal Stress

Rafting of the nickel-base single crystal superalloy CMSX-2 was investigated under the condition of high thermal stress using a newly constructed experimental equipment. The test piece with the diameter of 25 mm was tested at the maximum material temperature of 1 000 degree Celsius for 80 hours. The results showed that the raft structure occurred only under the influence of thermal stress. The raft structure developed parallel to the direction of the compressive thermal stress because of negative lattice misfit. The thickness of gamma phase and gamma prime phase in rafting increase with the increase in the temperature and the thermal stress.