247DS镍基合金侧钎焊预烧结预制体疲劳裂纹扩展研究

IF 5.7 2区材料科学 Q1 ENGINEERING, MECHANICAL

International Journal of Fatigue Pub Date : 2025-03-29 DOI:10.1016/j.ijfatigue.2025.108961

Ashok Bhadeliya , Birgit Rehmer , Birgit Skrotzki , Torsten Jokisch , Jürgen Olbricht , Bernard Fedelich

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引用次数: 0

摘要

预烧结预制体（PSP）钎焊用于镍基合金燃气轮机部件的修复，包括修复涡轮叶片和叶片的表面和尺寸。本研究研究了采用侧钎焊PSP材料的247DS合金试样的疲劳裂纹扩展（FCG）行为，模拟了这种修复过程中形成的典型夹层结构。对PSP层厚度分别为1.5 mm、2 mm、3 mm和4.5 mm的试样在950℃高温、应力比(R)为0.1的条件下进行FCG试验，评估PSP层厚度对疲劳裂纹扩展行为的影响。通过断口和金相分析，阐明了两种材料的潜在裂纹扩展机制和微观组织特征。结果表明，裂纹始终在PSP材料中开始，起源于启动缺口，特别是在预裂阶段的试样角处。此外，PSP材料中的裂纹扩展始终领先于247DS合金中的裂纹。这种裂纹扩展行为归因于PSP与母材之间的弹性性能差异和微观结构差异。金相分析表明，PSP材料内部存在孔隙和脆性析出物，导致晶间裂纹扩展速度加快。相反，合金247DS呈现出穿晶裂纹扩展，有助于观察到裂纹扩展行为。本研究证明了标准FCG测试方法的适用性，以及一种在两种材料中同时发生裂纹扩展的夹层试样中表征FCG行为的方法，从而初步了解了具有侧钎焊PSP的合金247DS的裂纹扩展行为。

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Fatigue crack growth in nickel-based alloy 247DS with side-brazed pre-sintered preform

Pre-sintered preform (PSP) brazing is employed in the repair of gas turbine components made of nickel-based alloys, including restoring the surface and dimensions of turbine blades and vanes. This study investigates the fatigue crack growth (FCG) behavior of Alloy 247DS specimens with side-brazed PSP material, mimicking a typical sandwich structure formed during such repairs. FCG tests were conducted at an elevated temperature of 950 °C and a stress ratio (R) of 0.1 on specimens with PSP layer thicknesses of 1.5 mm, 2 mm, 3 mm, and 4.5 mm to assess the influence of PSP thickness on fatigue crack growth behavior. Fractographic and metallographic analyses were performed to elucidate the underlying crack growth mechanisms and the microstructural characteristics of both materials. The results revealed that a crack consistently initiated in the PSP material, originating from the starter notch, particularly at the specimen corner during the pre-cracking phase. Additionally, crack propagation in the PSP material consistently advanced ahead of the crack in the Alloy 247DS. This crack growth behavior is attributed to the difference in elastic properties and microstructural differences between the PSP and base material. Metallographic analysis revealed the presence of porosity and brittle precipitates within the PSP material, which led to faster intergranular crack growth. Conversely, Alloy 247DS exhibited transgranular crack growth, contributing to the observed crack propagation behavior. This study demonstrates the applicability of standard FCG testing methods and an approach to characterize the FCG behavior in sandwich specimens, where crack growth occurs simultaneously in both materials, providing a preliminary understanding of crack growth behavior in Alloy 247DS with side-brazed PSP.

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来源期刊

International Journal of Fatigue 工程技术-材料科学：综合

CiteScore

10.70

自引率

21.70%

发文量

619

审稿时长

58 days

期刊介绍： Typical subjects discussed in International Journal of Fatigue address: Novel fatigue testing and characterization methods (new kinds of fatigue tests, critical evaluation of existing methods, in situ measurement of fatigue degradation, non-contact field measurements) Multiaxial fatigue and complex loading effects of materials and structures, exploring state-of-the-art concepts in degradation under cyclic loading Fatigue in the very high cycle regime, including failure mode transitions from surface to subsurface, effects of surface treatment, processing, and loading conditions Modeling (including degradation processes and related driving forces, multiscale/multi-resolution methods, computational hierarchical and concurrent methods for coupled component and material responses, novel methods for notch root analysis, fracture mechanics, damage mechanics, crack growth kinetics, life prediction and durability, and prediction of stochastic fatigue behavior reflecting microstructure and service conditions) Models for early stages of fatigue crack formation and growth that explicitly consider microstructure and relevant materials science aspects Understanding the influence or manufacturing and processing route on fatigue degradation, and embedding this understanding in more predictive schemes for mitigation and design against fatigue Prognosis and damage state awareness (including sensors, monitoring, methodology, interactive control, accelerated methods, data interpretation) Applications of technologies associated with fatigue and their implications for structural integrity and reliability. This includes issues related to design, operation and maintenance, i.e., life cycle engineering Smart materials and structures that can sense and mitigate fatigue degradation Fatigue of devices and structures at small scales, including effects of process route and surfaces/interfaces.