Determination of novel assessment criteria for the Evaluation of welding-related micro cracks using high resolution synchrotron-refraction-computer-tomography

确定使用高分辨率同步加速器折射计算机断层扫描评估焊接相关微裂纹的新评估标准

• 批准号: 388600999
• 负责人: Professor Dr.-Ing. Thomas Kannengießer
• 金额: --
• 依托单位: Bundesanstalt für Materialforschung und -prüfung (BAM)
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2017
• 资助国家: 德国
• 起止时间: 2016-12-31 至 2020-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/388600999?language=en
• 关键词: Determination; novel; assessment; criteria; Evaluation

The welding processing of innovative materials is always connected with high requirements. By minor imperfections a safe integrity of welding constructions can not be guaranteed when subjected to stresses. In this context, micro-cracks in µm-range present a serious danger because a detection by non-destructive testing may not be possible or is limited because the size of the cracks is mostly smaller than the resolution of conventional X-ray techniques. Due to the high safety significance and the very high costs for purchasing and processing, specifically for nickel-base alloys, it is of high interest to analyse reasons for micro-crack formation and to create corrective actions for avoiding cracks.Nickel-base alloys tend to form micro-cracks of the type ductility dip cracking (DDC) during welding. Below recrystallization during cooling of the weld seam a decrease of deformability appears. When critical strains are exceeded intergranular cracks occur in the solid state. The micro-cracks are formed in the filler metal or in the heat affected zone (HAZ). Causes for crack formation are currently unknown, but in literature grain size and precipitation condition on grain boundaries are referred to as main influences. Previous investigations concentrated on filler metal and HAZ of the base material. However, analyses on real structures of a HAZ with different precipitation conditions and, therefore, different grain structures, have not taken place yet.Therefore, the research objective is the determination of innovative evaluation criteria of micro-cracking in the HAZ of welds. Micro-cracks are characterised and quantified by means of high-resolution synchrotron-refraction-computer-tomography. The strain-to-fracture (STF) test is used to create cracks during thermo-mechanical loads of the base material. Two nickel-base alloys with the same alloy matrix but different precipitation conditions are compared. Moreover, physical simulated structures of a HAZ enable the correlation between microstructure, precipitation kinetics and grain structure. Based on these results temperature-strain curves will be developed for different areas of the HAZ.Finally, it is the goal of the studies to create an extended model for micro-crack formation, which includes both thermo-mechanical and microstructure specific influence factors as well as evaluation criteria including a voluminous network of cracks. With given material factors a statement about the susceptibility against micro-cracking in the HAZ should be made. In a renewal proposal the results will be verified on multi-layer welds under restraint.

创新材料的焊接加工总是与高要求联系在一起。当受到应力时，焊接结构的安全完整性不能通过微小的缺陷得到保证。在这种情况下，微米范围内的微裂纹存在严重的危险，因为通过非破坏性测试进行检测可能是不可能的，或者是有限的，因为裂纹的尺寸大多小于传统X射线技术的分辨率。由于镍基合金的高安全性和采购及加工成本非常高，因此分析微裂纹形成的原因并制定避免裂纹的纠正措施是非常重要的。镍基合金在焊接过程中容易形成延性浸渍裂纹（DDC）类型的微裂纹。在焊缝冷却过程中再结晶以下，变形能力出现下降。当超过临界应变时，在固态中发生晶间裂纹。微裂纹形成于钎料或热影响区（HAZ）。裂纹形成的原因目前尚不清楚，但在文献中，晶粒尺寸和晶界上的析出条件被认为是主要影响因素。以往的研究主要集中在钎料和母材热影响区。然而，对具有不同析出条件和不同晶粒结构的HAZ的真实的结构的分析还没有发生，因此，研究的目标是确定焊缝HAZ中微裂纹的创新性评价标准。微裂纹的特点和量化的高分辨率同步辐射折射计算机断层扫描仪。断裂应变（STF）测试用于在基材的热机械载荷期间产生裂纹。比较了两种具有相同合金基体但析出条件不同的镍基合金。此外，热影响区的物理模拟结构使显微组织，沉淀动力学和晶粒结构之间的相关性。基于这些结果的温度-应变曲线将开发为不同区域的HAZ.Finally，它是研究的目标，以创建一个扩展模型的微裂纹形成，其中包括热机械和微观结构的具体影响因素，以及评估标准，包括一个庞大的网络裂纹。对于给定的材料因素，应说明热影响区对微裂纹的敏感性。在更新提案中，将在约束条件下的多层焊缝上验证结果。

项目成果

Quantitative Analysis of Hydrogen‐Assisted Microcracking in Duplex Stainless Steel through X‐Ray Refraction 3D Imaging

通过 X 射线折射 3D 成像定量分析双相不锈钢中的氢辅助微裂纹

• DOI: 10.1002/adem.202101287
• 发表时间: 2022
• 期刊: Advanced Engineering Materials
• 影响因子: 3.6
• 作者: R. Laquai;T. Schaupp;A. Griesche;B. R. Müller;A. Kupsch;A. Hannemann;T. Kannengiesser;G. Bruno
• 通讯作者: G. Bruno