Product Code: ICAL05_1601

Crystalline Controlled Cladding of Ni-base Single Crystal Superalloy by Diode Laser
Authors:
Kazuyoshi Saida, Osaka University; Osaka Japan
Yoshihiro Fujita, Osaka University; Osaka Japan
Kazutoshi Nishimoto, Osaka University; Osaka Japan
Presented at ICALEO 2005

Microstructure and crystallographic orientation in the surface-melted region and clad region by diode laser have been investigated using Ni-base single crystal superalloy CMSX-4. The laser power and scanning speed in laser surface melting and cladding were varied while defocusing distance was constant. The microstructure and crystal orientation of the melted and clad regions were analyzed using SEM observation and electron backscattered pattern analysis. The surface-melted region under the low heat input condition was found to be solidified as the single-crystalline state with uni-directional dendrites which grew along the [001] directions. The surface-melted region under intermediate heat input condition was also single-crystalline with disoriented dendrites which grew along the [001], [010] and [100] directions. In contrast, the melted region under high heat input condition was consisted of polycrystal with stray crystals. Based on the theoretical analysis of growth direction of dendrite and the constitutional supercooling at the solidification front, the formation of stray crystals in a weld pool were predicted. The predicted results indicated that the stray crystal tended to be formed with increasing scanning speed and laser power. Microstructural observation revealed that the cladding layer grew epitaxially on the base metal substrate, and that multipass crystalline controlled cladding could be achieved by laser cladding with surface-remelting treatment of preceding beads.