Crystalline Controlled Filling Repairing Technique Utilizing Isothermal Solidification

Ni-base single crystal superalloy CMSX-4 has been widely used for turbine blades and vanes because of its superior heat-resistance. However, since they are usually used under severe environments, cracks sometime occur. Since this material is so expensive, there exists strong demand for repairing technique which enables to form singlecrystal in the repaired region to prevent deterioration of fatigue resistance. Therefore, in this study, the applicability of repairing technique utilizing iso-thermal solidification treatment with using Ni-Cr-B and Ni-Cr-Si alloys as filler metals to cracks occurred in single crystal superalloy CMSX-4 was investigated. The microstructure and crystal orientaion in the repaired regions under various heat treatment conditions were examined by SEM and EBSP. SEM and EBSP analyses have revealed that isothermal solidification and single-crystallization in the repaired region was achieved by repairing with using Ni-4Cr-2.5B filler metal under the condition of 1448K×176.4ks. The same result could be obtained also by using Ni-4Cr-10Si filler metal under the condition of 1473K×90ks. Creep rupture test for the repaired regions with Ni-4Cr-2.5B and Ni-4Cr-10Si filler metals has shown that the creep rupture strentgh of repaired region with Ni-4Cr-10Si filler metal reached about 2/3 of that of the base metal.