Activated diffusion brazed repair for IN738 hot section components of gas turbines

The wide-clearance activated diffusion brazing (ADB) techniques with various brazing alloys, namely DF4B and Nicrobraz 150 were applied to restore worn areas of IN738 components. In this study, the microstructure of an ADB joint and the results of thermal cyclic tests as well as tensile tests within the temperature range of from 25 to 980°C were investigated and discussed. The results of the tensile tests showed that ADB specimens brazed by 40 wt.% DF4B at 1190°C exhibited 85% tensile strength of the IN738 base materials at room temperature and retained the same strength as that of the base material at 980°C. However, the ductility of the ADB specimens with both brazing alloys was reduced. The results of cyclic-oxidation tests showed that ADB specimens with Nicrobraz 150 as the brazing alloy decayed after 150 cycles. However, the ADB specimens with DF4B had no obvious weight change until 205 cycles.