Laser surface treatment of Inconel 617 for next-generation nuclear reactors: A strengthening mechanisms study
Laser surface treatment of Inconel 617 for next-generation nuclear reactors: A strengthening mechanisms study
复制标题
DOI：
10.1016/j.matchar.2023.113024
复制
发表时间：
2023-08
影响因子：
4.7
通讯作者：
Noah Holtham;K. Davami
中科院分区：
文献类型：
--
作者：
Noah Holtham;K. Davami
随着Inconel合金617（IN 617）最近被ASME锅炉和压力容器核规范所接受，人们对开发制造方法有很大的兴趣，这些方法可以进一步放大其在强烈的热机械载荷情况下的有效性。在这项工作中，这样的一种方法，被称为激光喷丸，利用串联与热老化，以确定之间的关系的位错丰富的显微组织激光喷丸和强化相的析出行为。结果表明，单独激光喷丸后的表面硬度增加到226 HV以上的铸态值195 HV。时效热处理后，整个试样和激光喷丸区的显微硬度增加了额外的20%。微观结构的调查显示，晶粒尺寸或取向没有变化，虽然整个微观结构的碳化物沉淀导致在老化后更均匀的分散。透射电子显微镜观察发现，在激光喷丸表面附近有大量的纳米级γ'相弥散分布，平均面积分数为12.5%，此外还有高密度的位错（3 × 1014 lines/m2）。采用沉淀强化的Jackson-Reed模型和Taylor硬化关系分别确定γ'强化和加工硬化的影响。这两个模型都能够密切接近实验观察到的硬度数据，从而得出结论，主要的表面强化效果来自（i）析出的γ ′，和（ii）加工硬化效果，与来自（iii）残余应力，和（iv）碳化物强化的次要强化效果。本文概述的结果提出了一个有前途的，概念验证的使用激光喷丸引入表面机械性能增强的IN 617，下一代核反应堆应用的主要候选材料。
With the recent acceptance of Inconel Alloy 617 (IN617) for use under the ASME boiler and pressure vessel nuclear code, there is significant interest in developing manufacturing methods that can further magnify its effectiveness in intense thermo-mechanical loading scenarios. In this work, one such method, known as laser peening, was utilized in tandem with thermal aging to determine the relationship between the dislocation-rich microstructure following laser peening and the precipitation behavior of the strengthening phases. Results show that surface hardness after laser peening alone increased to 226 HV over the as-cast value of 195 HV. Following an aging heat treatment, the microhardness of the entire specimen and the laser peened zone increased by an additional 20%. Microstructural investigations revealed no change in grain size or orientation, though the precipitation of carbides throughout the microstructure resulted in a more homogenous dispersion after aging. Transmission electron microscopy revealed a rich dispersion of nanoscale γ’ phases with an average area fraction of 12.5%, in addition to a high density of dislocations (3 × 1014lines/m2) near the laser peened surface. The Jackson-Reed model of precipitate strengthening was used in tandem with the Taylor hardening relationship to determine the effects of γ’ strengthening and work hardening respectively. Both models were able to closely approximate the experimentally observed hardness data, leading to the conclusion that major surface strengthening effects result from (i) the precipitation of γ’, and (ii) work hardening effects, with minor strengthening effects coming from (iii) residual stresses, and (iv) carbide strengthening. The results outlined herein present a promising, proof-of-concept for the use of laser peening to introduce surface mechanical property enhancement for IN617, a prime candidate material for next-generation nuclear reactor applications.