Turbine blade tip single crystalline clad deposition with applied remelting passes for well oriented volume extension

The objective of this work was to achieve a single crystalline (SX) clad on the tip of an SX turbine blade. It was assumed that remelting could extend the SX-height by resolidifying the misoriented volume of its clad tracks. Thus, remelting was used as a tool to ease the clad epitaxy. All tests were performed with SX Ni-based superalloys CMSX-4 or PWA 1426. To determine the remelting parameters, the following methodology was devised: An ideal energy input per unit was determined for each clad track shape by applying a variable laser power during the process while traveling steadily. The energy value was defined using a combination of cross-sectional analyses and different laser parameters, thereby reducing the number of required tests to find the effective track remelting parameters. This was then tested thoroughly on five differently shaped CMSX-4 clad tracks to evaluate its validity. Thereafter, the remelting parameters from one chosen CMSX-4 track were applied to a similarly shaped PWA 1426 track, resulting in a complete SX clad track. This SX track was used to form the SX deposition on top of the blade, which was also made of PWA 1426. The tests to evaluate the remelting methodology were carried out on (010)/[100] or (010)/[001] crystalline orientations, which are equivalent to the orientations found on a turbine blade tip.