研究目的
To carry out a micro-structural study of laser beam welded GTD-111 subjected to specifically selected pre-weld and post-weld heat treatments to gain better understanding of the factors contributing to HAZ cracking in the alloy, which is vital in developing better procedure for preventing or minimizing cracking during welding of the alloy.
研究成果
The study concluded that liquation cracks in GTD-111 superalloy are associated with the constitutional liquation of γ′ particle, MC carbides, inter-dendritic γ-γ? eutectic, and melting of Cr-rich boride. Crack-free welds were achieved under specific heat treatment conditions. The hardness of the fusion zone was higher than that of HAZ and base metal zone, affecting liquation cracking susceptibility. The findings are crucial for developing better welding procedures for GTD-111 superalloy.
研究不足
The study focused on specific heat treatment cycles and welding parameters, which may not cover all possible conditions affecting weldability and cracking in GTD-111 superalloy. The mechanical properties and crack susceptibility were evaluated under controlled conditions, which may differ in real-world applications.
1：Experimental Design and Method Selection:
The study involved the use of Nd:YAG pulsed laser welding on GTD-111 nickel-based superalloy with various pre- and post-weld heat treatment cycles to investigate liquation, solidification, and strain-age cracks.
2：Sample Selection and Data Sources:
GTD-111 alloy with specific chemical composition was used. Several heat treatment cycles were designed based on the temperature of the GTD-111 solidus and the solution heat treatment temperature of other effective phases.
3：List of Experimental Equipment and Materials:
Nd:YAG pulsed laser processing system with a five axis CNC working system, pure argon as shielding gas, and standard mechanical polishing procedures for sample preparation.
4：Experimental Procedures and Operational Workflow:
Welding was performed under specific conditions including laser spot radius, average power, welding speed, frequency, pulse duration, focal distance, and spot size. Metallographic samples were prepared, etched, and characterized by optical microscope and FESEM.
5：Data Analysis Methods:
The extent of liquation and solidification cracks was determined by measuring the total crack length in sections of each welded specimen using FESEM and image j software. Mechanical properties were assessed through tensile and micro-hardness tests.
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