ABSTRACT

The present study investigates susceptibility of Inconel 617 to liquation cracking in laser-based welding techniques such as autogenous laser welding (ALW) and laser-MIG hybrid welding (LHW) with variation in heat input. Advanced characterization techniques such as high-speed Nano-Indentation testing and micro X-ray diffraction techniques were utilized to analyze microstructural variations in correlating mechanical behavior of low-melting eutectics formed in partially melted zone (PMZ). Results indicated that the liquation cracking in PMZ was associated with the constitutional liquation reaction between intermetallic carbides and austenite matrix. With increase in heat input, its susceptibility reduced, although with enhancement in grain-boundary liquid film formation and was associated with the constitutional liquation of (Cr, Mo)-rich M₂₃C₆ carbides and γ matrix. Combined effect of induced thermal stress with presence of low-melting eutectics in partially melted zone was found to greatly influence liquation-cracking susceptibility in both the welding processes. Indeed, ternary eutectic comprising metallic carbides of Cr and Mo and austenite-matrix with low nano-hardness values compared to that of hard carbides present in base metal and weld fusion zone re-confirmed their influence on cracking susceptibility. Increase in heat input enhanced dissolution of Mo-rich M₆C carbides that attributed to stress-relaxation and thereby reduce cracking propensity.

摘要

本研究调查了Inconel 617在基于激光的焊接技术（例如自生激光焊接（ALW）和激光-MIG混合焊接（LHW））中随着热输入变化而对液化裂纹的敏感性。先进的表征技术，例如高速纳米压痕测试和微X射线衍射技术，被用来分析与部分熔融区（PMZ）中形成的低熔点共晶力学行为相关的微观结构变化。结果表明，PMZ中的液化开裂与金属间碳化物与奥氏体基体之间的液化反应有关。随着热输入的增加，其敏感性降低，尽管随着晶界液膜形成的增加而增加，并且与富含（Cr，Mo）的M的结构性液化有关。₂₃ C ₆碳化物和γ基体。研究发现，在两个熔化过程中，感应热应力与部分熔化区中存在低熔点共晶的综合作用会极大地影响液化裂纹敏感性。实际上，与贱金属和焊接熔合区中存在的硬质碳化物相比，包含Cr和Mo的金属碳化物和具有低纳米硬度值的奥氏体基体的三元共晶再次证实了它们对开裂敏感性的影响。热输入的增加增强了富钼的M ₆ C碳化物的溶解，这归因于应力松弛，从而降低了开裂倾向。