In-situ load analysis in multi-run welding using LTT filler materials

Dixneit, Jonny; Kromm, Arne; Hannemann, Andreas; Friedersdorf, P.; Kannengießer, Thomas; Gibmeier, Jens

doi:10.1007/s40194-016-0373-1

Cited by 10 publications

(5 citation statements)

References 12 publications

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“…The subject of low transformation temperature (LTT) has been intensively studied [1,2]. In particular, the proof that compressive residual stresses are formed [3,4], the investigation of the mechanisms of stress formation [5,6], and the effect on the fatigue strength [7,8] have been the subject of many research projects. Recent publications also deal with extended topics such as microstructure and the associated mechanical properties [9][10][11][12][13], the behaviour during multilayer welding [14][15][16][17][18], and the application of LTT in beam welding [19].…”

Section: Ltt Filler Metalsmentioning

confidence: 99%

Surface- and volume-based investigation on influences of different Varestraint testing parameters and chemical compositions on solidification cracking in LTT filler metals

et al. 2020

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The subject of this study is how, and to what extent, Varestraint/Transvarestraint test results are influenced by both testing parameters and characteristics of evaluation methods. Several different high-alloyed martensitic LTT (low transformation temperature) filler materials, CrNi and CrMn type, were selected for examination due to their rather distinctive solidification cracking behaviour, which aroused interest after previous studies. First, the effects of different process parameter sets on the solidification cracking response were measured using standard approaches. Subsequently, microfocus X-ray computer tomography (μCT) scans were performed on the specimens. The results consistently show sub-surface cracking to significant yet varying extents. Different primary solidification types were found using wavelength dispersive X-ray (WDX) analysis conducted on filler metals with varying Cr/Ni equivalent ratios. This aspect is regarded as the main difference between the CrNiand CrMn-type materials in matters of cracking characteristics. Results show that when it comes to testing of modern highperformance alloys, one set of standard Varestraint testing parameters might not be equally suitable for all materials. Also, to properly accommodate different solidification types, sub-surface cracking has to be taken into account.

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Section: Ltt Filler Metalsmentioning

confidence: 99%

Surface- and volume-based investigation on influences of different Varestraint testing parameters and chemical compositions on solidification cracking in LTT filler metals

et al. 2020

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“…In addition, the use of low transformation temperature (LTT) alloys can effectively reduce the accumulation of tensile stress. This is because the low transformation temperature alloy can use the expansion of martensite transformation to offset part or all of the heat shrinkage, thereby reducing the residual tensile stress [55]. However, it is important to note that the melting and cooling behavior of the laser cladding pool is highly complex, and residual stresses are challenging to eliminate entirely.…”

Section: Constraint Stressmentioning

confidence: 99%

Crack Formation Mechanisms and Control Methods of Laser Cladding Coatings: A Review

Li¹,

Huang²,

Yi³

2023

Coatings

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Laser cladding, a novel surface treatment technology, utilizes a high-energy laser beam to melt diverse alloy compositions and form a specialized alloy-cladding layer on the surface of the substrate to enhance its property. However, it can generate substantial residual stresses during the rapid cooling and heating stages, due to inadequate selection of cladding process parameters and disparities in thermophysical properties between the clad layer and substrate material, leading to the formation of various types of cracks. These cracks can significantly impact the quality and performance of the coating. This paper presents a comprehensive review of crack types and their causes in laser cladding coatings, and identifies that three primary sources of residual stresses, thermal stress, organizational stress, and restraint stress, are the fundamental causes of crack formation. The study proposes several strategies to control coating cracks, including optimizing the coating layer material, refining the coating process parameters, incorporating heat treatment, applying auxiliary fields, and utilizing numerical simulations to predict crack initiation and propagation. Additionally, the paper summarizes crack control methods for emerging structural materials and novel preparation processes. Lastly, the paper analyzes the prospects, technical approaches, and key research directions for effectively controlling cracks in laser cladding coatings.

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“…Its effectiveness has been proven in numerous research projects (e.g., References [1][2][3][4][5]. Most of the works deal with the basic verification of the generated residual compressive stresses [6][7][8] and/or their influence on the fatigue strength [9][10][11]. Comprehensive overviews can be found from Ooi et al [12] and Kromm et al [2].…”

Section: Introductionmentioning

confidence: 99%

Solidification Cracking Assessment of LTT Filler Materials by Means of Varestraint Testing and µCT

et al. 2020

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Investigations of the weldability of metals often deal with hot cracking, as one of the most dreaded imperfections during weld fabrication. The hot cracking investigations presented in this paper were carried out as part of a study on the development of low transformation temperature (LTT) weld filler materials. These alloys allow to mitigate tensile residual stresses that usually arise during welding using conventional weld filler materials. By this means, higher fatigue strength and higher lifetimes of the weld can be achieved. However, LTT weld filler materials are for example, high-alloyed Cr/Ni steels that are susceptible to the formation of hot cracks. To assess hot cracking, we applied the standardized modified varestraint transvarestraint hot cracking test (MVT), which is well appropriate to evaluate different base or filler materials with regard to their hot cracking susceptibility. In order to consider the complete material volume for the assessment of hot cracking, we additionally applied microfocus X-ray computer tomography (µCT). It is shown that by a suitable selection of welding and MVT parameter the analysis of the complete 3D hot crack network can provide additional information with regard to the hot cracking model following Prokhorov. It is now possible to determine easy accessible substitute values (e.g., maximum crack depth) for the extent of the Brittleness Temperature Range (BTR) and the minimum critical strain P m i n .

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In-situ load analysis in multi-run welding using LTT filler materials

Cited by 10 publications

References 12 publications

Surface- and volume-based investigation on influences of different Varestraint testing parameters and chemical compositions on solidification cracking in LTT filler metals

Surface- and volume-based investigation on influences of different Varestraint testing parameters and chemical compositions on solidification cracking in LTT filler metals

Crack Formation Mechanisms and Control Methods of Laser Cladding Coatings: A Review

Solidification Cracking Assessment of LTT Filler Materials by Means of Varestraint Testing and µCT

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