Microstructure of Laser Clad Ni-Cr-Al-Hf Alloy on a Gamma Strenghtened Ni-Base Superalloy

摘要

Alloys and coatings for alloys for improved high temperature service life under aggressive atmospheres are of great contemporary interest. There is a general consensus that the addition of rare earths such as Hf will provide many beneficial effects for such alloys. The laser cladding technique was used to produce Ni-Cr-Al-Hf alloys with extended solid solution of Hf. A 10 kW CO2 laser with mixed power feed was used for laser cladding. Optical, scanning electron (SEM) and scanning transmission electron (STEM) microscopy were employed to characterize the microstructure of alloys produced during laser cladding processes. Microstructural studies revealed grain refinement, considerable increase in solubility of Hf in the matrix, Hf-rich precipitates, and new metastable phases. The size and morphology of (Ni3Al) phase were discussed in relation to its microchemistry and the laser processing conditions. This paper will report the microstructural development in this laser clad Ni-Cr-Al-Hf alloy. (JES)