Rupture behavior and fracture mode for Inconel 625–9% Cr steel dissimilar welded joints at high temperature

Coupled effect of temperature and stress on the microstructure and stress rupture behavior of 9% Cr-CrMoV dissimilar welded joints

The weld metal (WM) was generally regarded as one of the weakest zones in the dissimilar welded joints. The microstructure and fracture mechanism of the multi-pass WM are systematically probed in the present study. The scanning electron microscopy (SEM) results show more voids in the equiaxed grain zone (EGZ) adjacent to the fracture than those in the columnar grain zone (CGZ). The transmission electron microscopy (TEM) results reveal that the precipitates are mainly Cr-rich M23C6 and Mo-rich M6C phases. The voids were initiated by the mismatch deformation between the precipitates and matrix during the stress rupture test. Moreover, the voids could easily extend and converge to form the macro cracks in the EGZ.

Stress rupture initiated by the carbides in the grain boundaries of the multi-pass weld metal

Inconel 625 superalloy (IN625) was generally welded as the base metal to fabricate the rotors in steam turbine with temperature over 700 °C. In this case the weakening modes for the heat affected zone (HAZ) in IN625 welded joints during the stress rupture test are systematically investigated in the present study. The stress rupture test results show a dependence of rupture time on stress lg (t) = −0.017 σ + 5.85, which can be achieved to predict the rupture life with different stress levels. Besides, all the samples are deemed as intergranular fracture with columnar grain morphology appeared on the fracture surface. The microhardness distribution reflects that all the specimens ruptured in the HAZ. It is deemed that the chain-like particles can weaken the binding force of the continuous grains and therefore cause the resultant fracture in the region with comparative low microhardness of HAZ. With the decrease of the applied stress, the formation of acicular δ phase (Ni3Nb) can reduce the deformation capacity of the HAZ by consuming the precipitate strengthened element Nb. Hence, the micro-voids tend to initiate along the grain boundaries. The coarse Laves phase particles with hard and brittle features become the dominated factor with the further increased rupture time. The micro-voids initiate and converge around the Laves phase under the stress to form micro-cracks, eventually cause the fracture of the ruptured specimens.

Weakening modes for the heat affected zone in Inconel 625 superalloy welded joints under different high temperature rupture conditions

Fatigue crack growth (FCG) behavior of 9Cr/CrMoV dissimilar welded joint at elevated temperature and different stress ratios was investigated. Attention was paid to the region near the fusion line of 9Cr where carbon-enriched zone (CEZ) and carbon-depleted zone (CDZ) formed due to carbon migration during the welding process. Hard and brittle tempered martensite dominated the stress ratio-insensitive FCG behavior in the coarse grain zone (CGZ) of 9Cr-HAZ. For crack near the CGZ–CEZ interface, crack deflection through the CEZ and into the CDZ was observed, accompanied by an accelerating FCG rate. Compared with the severe plastic deformation near the secondary crack in 9Cr-CGZ, the electron back-scattered diffraction analysis showed less deformation and lower resistance in the direction toward the brittle CEZ, which resulted in the transverse deflection. In spite of the plastic feature in CDZ revealed by fracture morphology, the less carbides due to carbon migration led to lower strength and weaker FCG resistance property in this region. In conclusion, the plasticity deterioration in CEZ and strength loss in CDZ accounted for the FCG path deflection and FCG rate acceleration, respectively, which aggravated the worst FCG resistance property of 9Cr-HAZ in the dissimilar welded joint.

Effect of Carbon Migration on Interface Fatigue Crack Growth Behavior in 9Cr/CrMoV Dissimilar Welded Joint

Liquation cracks are generally regarded as thermal defects in various materials, e.g. in steels and nickel-based alloys. However, direct observation of microstructure with crack-like morphology that may be revealed by chemical etching or electrochemical etching methods, might lead to the misinterpretation of liquation cracks. To avoid the possible misinterpretation, comparative etching was employed to reveal the effect of various etching processes on the determination of liquation cracks. As a result, the formation process and mechanism of the false liquation crack in 9% Cr/CrMoV welded joint were clarified. The results obtained by optical microscope (OM) and scanning electron microscope (SEM) in the heat treatment zone of 9% Cr steel (9% Cr-HAZ) after chemical etching clearly demonstrate the existence of crack-like morphology, and the disappearance of element segregation zone after regrinding and re-polishing. Besides, laser scanning confocal microscope (LSCM) was applied to further exhibit the microstructure evolution experiencing high temperature to confirm the possibility of the liquation crack. The results showed that the element segregation and subsequent chemical etching process were the crucial factors to cause the formation of false liquation crack.

Clarification of the false liquation crack existed in 9% Cr/CrMoV dissimilar welded joint by comparative etching process and in situ laser scanning confocal microscope

Handle everyday research tasks with reliable, citation-backed results

Your personal Research Agent to handle research tasks with citation-backed results

Popular Tasks used by Researchers

How can I help with your research?

Meet SciSpace

Get more enhanced response by uploading the PDFs you want me to reference.

No relevant PDFs in your library

SciSpace is the AI research assistant for academics. Run systematic literature reviews on 280M+ papers, and write papers with cited sources. Trusted by 1M+ students, PhDs & researchers.

SciSpace | AI for Research

Analyze PDFs

Code & Manuscripts

Funding & Grants

Literature & Patents

Medical & Clinical Data

Systematic Review

Visualize & Present

Web & Data

Build a Google Scholar-like website for your research.

Build a website

Create charts and images for your research

Create a Chart

Write a paper for submission to a journal

Draft a manuscript

Patent Search

Design eye-catching scientific posters in minutes.

Scientific Poster Generation

Systematic Literature Review

One task is running at the moment. Your messages will be shown right after.

Drag and drop or click here to browse

Loved by <highlight>1 million+</highlight> researchers

Extract a list of specific topics and their sources from unstructured text

Topics

Compare and analyze relevant papers that matches with your search

Papers

Get insights from PDFs and bookmarked papers from your library

My library

Recent searches

Try searching for:

Catch AI-generated content in scholarly and non-scholarly content

{ai} Detector

Ai Writer

Get PDF Summaries, highlighted text explanations 

Chat with PDF

Effortlessly create in-text citations and bibliographies in APA and 2,500 other formats

Citation generator

Get explanations, summaries, and answers on academic papers

Ease up your research workflow with {scispace}'s cohort of exciting AI tools

Elevate your academic writing skills and convey your ideas the way you want

Paraphraser

Explore our range of reading and writing tools

Your file is being prepared and should be ready in a few minutes. If it's a large file, it might take a bit longer. You can close this window, and we'll email you the file when it's done.

You have reached a maximum limit of <strong>{limit}</strong> columns in the table. Remove at least <strong>1</strong> column to add or create another one.

Yuming Ding

Author Tools

Chat about Author

Papers

Clarification of the false liquation crack existed in 9% Cr/CrMoV dissimilar welded joint by comparative etching process and in situ laser scanning confocal microscope