Microstructure evolution and columnar to equiaxed transition of oxide dispersion strengthened nickel-based superalloy fabricated by laser metal deposition: From single/multi-track process optimization to bulk sample

Abstract

As a result of their excellent creep strength at high temperatures, oxide dispersion strengthened alloys are attractive candidates as structural materials for high temperature applications. However, traditional production processes encounter several challenges when producing complex shape. This study employed a single/multi-track process optimization approach for the preparation of oxide dispersion strengthened nickel-based superalloy by laser metal deposition. A multi-objective optimization method (power, scanning speed, powder feed rate) was adopted in the preparation process to improve the dilution, wetting angle, powder capture efficiency and hardness of the single-track. The Taguchi method-Principal component analysis-Gray relational analysis-Response surface methodology was used to optimize the characteristics of single-track. Thermocapillary convection drives the motion of gas bubbles in single-track depositions, while surface pores typically cluster along the track edge. The microstructure and crack of multi-track are optimized by overlapping ratio. In order to investigate the effect of the transition from columnar to equiaxed, the microstructure of the laser-deposited bulk specimen was studied. The results verify the feasibility of multi-objective process optimization in track and present experience for the application of microstructure and mechanical properties of track process optimization laser-deposited sample.