马氏体不锈钢闸阀阀杆的失效分析和回火热处理

IF 4.4 2区工程技术 Q1 ENGINEERING, MECHANICAL

Engineering Failure Analysis Pub Date : 2025-04-07 DOI:10.1016/j.engfailanal.2025.109591

H.R. Lashgari , M. Asnavandi , Ji Zhang , Yang Liu , Sean Li

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引用次数: 0

摘要

本研究调查了用于海水淡化厂的431级马氏体不锈钢阀杆的失效。显微组织分析显示，断口附近晶界处存在未回火马氏体、δ铁素体（δ）和碳化铬（M23C6，其中M=Cr, Fe）。这些发现表明在制造过程中热处理不当，导致了敏化的微观结构。富cr区和贫cr区之间微原电池的形成导致敏化区域的微点蚀和局部攻击（靠近压盖填料/齿轮箱端），最终由于过载而失效。在环境温度下进行的Charpy冲击试验的产生值约为10 J，表明敏化微观结构具有明显的脆性。431级不锈钢的回火热处理（在1020℃下奥氏体化1小时，然后在600℃回火2小时）成功地恢复了回火马氏体组织，显著提高了耐腐蚀性（大约提高了3.5倍）。热分析表明，在1150℃左右，组织变为奥氏体，但一旦形成就不能溶解δ铁素体。随后的热钙模拟证实了这一点，结果表明，如果温度过高，钢凝固时含有大量的δ铁素体，并且在热处理过程中形成δ铁素体。

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Failure analysis and rejuvenation heat treatment of a martensitic stainless steel gate valve stem

The present study investigated the failure of a martensitic stainless steel valve stem, Grade 431, used in a desalination plant. Microstructural analysis revealed the presence of untempered martensite, delta ferrite (δ), and chromium carbides (M₂₃C₆, where M=Cr, Fe) at the grain boundaries adjacent to the fracture surface. These findings indicate improper heat treatment during manufacturing, resulting in a sensitized microstructure. The formation of microgalvanic cells between Cr-rich and Cr-depleted zones led to micropitting and localised attack (near the gland packing/gearbox end) in the sensitized areas, which eventually failed due to overload. The Charpy impact test conducted at ambient temperature yielded values of approximately 10 J, demonstrating significant brittleness in the sensitized microstructure. A rejuvenation heat treatment typical for 431-grade stainless steels (austenitizing at 1020 °C for 1 h, followed by tempering at 600 °C for 2 h) successfully restored the tempered martensitic microstructure, significantly improving corrosion resistance (by approximately 3.5 times). Thermal analysis showed that the microstructure becomes austenitic at approximately 1150 °C, but is unable to dissolve delta ferrite once formed. This was later confirmed by Thermo-Calc simulations, which indicated that the steel solidifies with a high fraction of delta ferrite and/or forms delta ferrite during heat treatment if the temperature is excessive.

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来源期刊

Engineering Failure Analysis 工程技术-材料科学：表征与测试

CiteScore

7.70

自引率

20.00%

发文量

956

审稿时长

47 days

期刊介绍： Engineering Failure Analysis publishes research papers describing the analysis of engineering failures and related studies. Papers relating to the structure, properties and behaviour of engineering materials are encouraged, particularly those which also involve the detailed application of materials parameters to problems in engineering structures, components and design. In addition to the area of materials engineering, the interacting fields of mechanical, manufacturing, aeronautical, civil, chemical, corrosion and design engineering are considered relevant. Activity should be directed at analysing engineering failures and carrying out research to help reduce the incidences of failures and to extend the operating horizons of engineering materials. Emphasis is placed on the mechanical properties of materials and their behaviour when influenced by structure, process and environment. Metallic, polymeric, ceramic and natural materials are all included and the application of these materials to real engineering situations should be emphasised. The use of a case-study based approach is also encouraged. Engineering Failure Analysis provides essential reference material and critical feedback into the design process thereby contributing to the prevention of engineering failures in the future. All submissions will be subject to peer review from leading experts in the field.