Optimum results of metallic-solids diffusion welding require very high temperatures and pressures. Using suitable presses, pressures of at least 25 megapascal must be generated at temperatures above 1,000°C for components made of materials with high melting temperatures such as highly heat-resistant steel. Components with cavities or hollows tend to deform when subject to such enormous pressure and heat. KIT's Institute for Applied Materials - Applied Materials Physics (IAM-AWP) has developed a method for deformation-free manufacture of complex hollow structures in massive components. This new method even allows low-deformation welding of components with bent and angled ducts. For that purpose, pipes of identical materials are reproduced and are accurately fitted in the cavities as supporting structures. The respective components then are vacuum-sealed by means of an electron beam method. Subsequently, the self-encapsulating part is diffusion-welded in a hot isostatic press (HIP). The specially integrated supporting structures keep the cavities from buckling and deforming in the presence of high pressures and temperatures. Using such supporting structures, even extremely complex hollow geometries can be integrated in large components. Besides, the new method ensures double safety as regards the leak tightness of process components: Since each insert, prior to implementation, is being pressure-tested and each finished component is subjected to a strict quality inspection process, the technology complies with the highest pressure vessel and reactor safety requirements and is suited, for example, for construction of sophisticated reactor or turbine cooling systems.