Determining the Dependence of Deformation during Diffusion Welding on the Aspect Ratio Using Samples Made of SS 304 (1.4301)

Gietzelt, Thomas; Toth, V.; Huell, Andreas; Dittmeyer, Roland

doi:10.1002/adem.201600344

Cited by 13 publications

(8 citation statements)

References 6 publications

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“…Even for fixed values for bonding temperature, bearing pressing and dwell time, the deformation varies. Also the number of layers to be joined contributes to the value of deformation since for each sheet the surface roughness must be levelled [4].…”

Section: Resultsmentioning

confidence: 99%

Impact of scratch depth on vacuum tightness of diffusion bonded parts

Gietzelt

Hull

Toth

et al. 2018

Materialwissenschaft Werkst

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The surface roughness or solitary grooves decides about success or failure of diffusion bonding and vacuum tightness of the parts to be welded. Since surfaces have to be mated at atomic level to enable diffusion of atoms across bonding planes, also single deep scratches must be avoided to achieve vacuum tightness. Up to now there are no criteria which grooves can be tolerated. In fact, personal experience of the operator is essential to evaluate the surface before diffusion bonding. In this paper different load on top of a spike made of hard metal and sliding across the surface of austenitic stainless steel sheets of 1.4301 are employed to prepare grooves of different depth. A scanning electron microscope is used to visualize the dimension of the grooves. By white light interferometry, the depths according the load of the spice is evaluated. Diffusion bonding is performed at T = 1075 °C, t = 4 h, p = 12 MPa as well as with additional short peak loads. It turns out that the depth of grooves corresponds very well with the degree of leakage rate. Hence, by measuring the depth of grooves, prediction of leak rate can be predicted.

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Section: Resultsmentioning

confidence: 99%

Impact of scratch depth on vacuum tightness of diffusion bonded parts

Gietzelt

Hull

Toth

et al. 2018

Materialwissenschaft Werkst

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“…Deformation depends not only on the material used and on the parameters of temperature, bearing pressure, and dwell time, but also on the aspect ratio and design of microstructured parts. For example, deformation may double or even triple for large, but very flat samples with higher aspect ratios …”

Section: Results and Conclusionmentioning

confidence: 99%

Challenges of Diffusion Bonding of Different Classes of Stainless Steels

Gietzelt¹,

Toth²,

Huell³

2017

Adv Eng Mater

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Solid state diffusion bonding is used to produce monolithic parts exhibiting mechanical properties comparable to those of the bulk material. This requires diffusion of atoms across mating surfaces at high temperatures, accompanied by grain growth. In case of steel, polymorphy helps to limit the grain size, since the microstructure is transformed twice. The diffusion coefficient differs extremely for ferritic and austenitic phases. Alloying elements may shift or suppress phase transformation until the melting range. In this paper, diffusion bonding experiments are reported for austenitic, ferritic, and martensitic stainless steels possessing varying alloying elements and contents. Passivation layers of different compositions are formed, thus affecting the local diffusion coefficient and impeding diffusion across faying surfaces. As a consequence, different bonding temperatures are needed to obtain good bonding results, making it difficult to control the deformation of parts, since strong nonlinearities exist between temperature, bonding time, and bearing pressure. For martensitic stainless steel, it is shown that it is very easy to obtain good bonding results at low deformation, whereas ferritic and austenitic stainless steels require much more extreme bonding parameters.

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“…For example, for disks of 160 mm in diameter, a deformation of 10% was obtained for a height of 10 mm for T = 1075°C, t = 4 h, p = 25 MPa. For a height of 150 mm, however, the deformation was more than 33% [22].…”

Section: Impact Of the Design Of Mechanical Micro-structures The Aspmentioning

confidence: 93%

Diffusion Bonding: Influence of Process Parameters and Material Microstructure

Gietzelt¹,

Toth²,

Huell³

2016

Joining Technologies

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Diffusion welding is a solid joining technique allowing for full cross-section welding. There is no heat-affected zone, but the whole part is subjected to a heat treatment. By diffusion of atoms across the bonding planes, a monolithic compound is generated.The process takes place in a vacuum or inert gas atmosphere at about 80% of the melting temperature and is run batch-wisely. Hence, it is rarely used despite its advantages to achieve holohedral joints and is widespread in the aerospace sector only.The quality of a diffusion-welded joint is determined by the three main parameters bonding temperature, time, and bearing pressure. The difficulty tailoring the process is that they are interconnected in a strong nonlinear way.Several additional factors may influence the result or may change the material, e.g. surface roughness and passivation layers, all kinds of lattice defects, polymorphic behaviour, and formation of precipitations at grain boundaries, design of the parts to be welded and its aspect ratio as well as mechanical issues of the welding equipment. Hence, experiments are necessary for almost each special part.In this chapter, an overview about the experience of diffusion welding is given. Influences are discussed in detail and conclusions are derived.

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Determining the Dependence of Deformation during Diffusion Welding on the Aspect Ratio Using Samples Made of SS 304 (1.4301)

Cited by 13 publications

References 6 publications

Impact of scratch depth on vacuum tightness of diffusion bonded parts

Impact of scratch depth on vacuum tightness of diffusion bonded parts

Challenges of Diffusion Bonding of Different Classes of Stainless Steels

Diffusion Bonding: Influence of Process Parameters and Material Microstructure

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