**Diffusion Bonding: Influence of Process Parameters and Material Microstructure**

Thomas Gietzelt, Volker Toth and Andreas Huell

Additional information is available at the end of the chapter

http://dx.doi.org/10.5772/64312

#### **Abstract**

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.

**Keywords:** diffusion welding, diffusion bonding, lattice defects, grain growth, precip‐ itation, sensitization, passivation layer

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