高超超临界燃煤火电机组（A-USC）中镍基高温合金构件具有厚尺度和长期安全服役的特殊性，焊接对其制造至关重要。然而，镍基高温合金厚壁构件焊接时易出现热裂纹，导致接头韧性与疲劳性能明显下降。镍基高温合金厚壁构件的高质量焊接具有相当难度和挑战。本项目针对镍基高温合金这一应用背景，以Inconel 617B厚板为材料对象，研究镍基高温合金厚板在激光焊接过程中热影响区的颗粒溶解与成分液化、熔池与液膜流动行为、元素物理化学冶金、熔体与液膜的瞬态凝固行为、应力演化和组织结构演变等科学问题，阐明该焊接过程热影响区和焊缝液化膜的形成机理，澄清液化膜迁移的热力学与动力学条件及其对瞬态凝固行为的影响，重点揭示该焊接过程中热裂纹的形成机制及其控制因素和临界条件，从而形成镍基高温合金厚板激光焊接热裂纹抑制的有效举措，为推动激光焊接技术在A-USC机组中镍基高温合金厚壁构件制造中的应用提供理论支撑。

Nickel-base high temperature alloy components for advanced ultra-supercritical (A-USC) coal-firing power plant are generally large in thickness and service at high-temperature for very long time. Welding is critical for manufacturing these components. However, hot cracks easily occur during welding of nickel-base high temperature alloy thick plates, which deteriorates toughness and fatigue properties of the joint. High quality welding of nickel-base high temperature alloy thick plates has considerable difficulties and challenges. In this project, we make a proposal to carry out fundamental research on laser welding of nickel-base alloy thick plates by using Inconel 617B as an example. Scientific problems, such as articles dissolution and constitute liquation，flow behavior of welding pool and liquation films, physical and chemical metallurgy of elements, transient solidification behavior of melted pool and liquation films, stress evolution and microstructure formation, et.al, will be investigated in detail. The formation mechanism and transient solidification behavior of liquation films in both weld seam and heat affected zone will be studied. Thermodynamics and dynamics of liquid film migration will be clarified to find out the correlation between it and transient solidification. The formation mechanism of hot cracks and its control factors and boundary condition will be elucidated, and then effective methods to avoid hot cracks during laser welding of nickel-base high temperature alloy thick plates will be put forward. Results of this project will be the theoretical foundation for laser welding of nickel-base high temperature alloy thick components for A-USC application.