ADVANCED MATERIALS & PROCESSES | MARCH 2026 14 Additive brazing is an innovative process for creating high-loadbearing and functional coatings. It allows for the diffusion bonding of components without the use of flux, making it particularly suitable for coating workpieces with a variety of special materials. Especially notable is the flexibility of the process in terms of coating thickness and hardness, which can be adjusted according to the specific requirements of the application. Two- or multi-component parts are not joined by solid-state bonding but are instead coated with brazing materials through diffusion bonding. Brazing materials specially adapted for this process are typically based on nickel, cobalt, iron, or copper alloys. Depending on the required coating function, hard materials can be added to tailor the properties. These include carbides, silicides, borides, oxides, and superhard phases such as diamond or cubic boron nitride. Among these, WC, CrC, and NbC are most commonly used. The hard material content of the coating can reach up to 80 wt% or more, allowing a wide adjustment range of coating hardness, from approximately 18–30 HRC up to 62–65 HRC. The mechanical strength of high-temperature brazed hard coatings is equivalent to that of the base material, resulting in a highly load-bearing composite layer. 2D and 3D geometries can be coated on both the inside and outside. Typical coating thicknesses range from 0.1 to 10 mm or more, with a typical thickness of 1.0 to 2.0 mm. A key advantage of the brazing coating process is its extremely high deposition efficiency, which can approach 100% when using tapes, preforms, slurries, or powders. The additive brazed coatings can take on various functions. For example, the hard particles introduced into the brazing material can be firmly brazed onto the component surface to provide wear protection or gripping functionality. Alternatively, worn components such as molds or turbine blades can be recontoured by inserting suitable materials in the form of tapes or slurries into the worn areas, which are then post-processed (Fig. 1). Recent developments also show the possibility of locally brazing applied tapes or suspensions using laser energy, without the need to heat the entire component. By selecting appropriate morphologies of the starting powders for the brazing matrix materials and hard materials, the coating system can be specifically optimized and adapted for the respective application. WHAT IS BRAZING? Brazing is a thermal joining process in which two or more metallic components are connected using a filler material that has a lower melting point than the components being joined. In contrast to welding, where the components themselves are melted, brazing keeps the base material solid, with the components being bonded together by the melting of the filler material. The filler, typically an alloy, is applied to the parts to be joined and heated until it melts, spreading into the joints between the components, where it forms a strong, permanent connection upon solidification. A distinctive feature of brazing is that the filler material has a melting temperature above 450°C, distinguishing it from low-temperature soldering processes such as soft soldering. Brazing can be carried out using different heating methods, including vacuum or protective gas furnaces, flame brazing, induction heating, and laser- based melting. The selection of the specific process route depends on the material system and manufacturing requirements. The brazed joint is primarily formed through capillary action and the diffusion of the filler material into the microcracks and gaps between the components. After heating, the filler cools in the gaps between the components, forming a solid metal bond. Brazing can be used to join a wide range of materials, such as metals, ceramics, or composite materials, and is suitable not only for simple joints but also for complex geometries. Depending on the type of filler used, different physical and mechanical properties can be achieved during the brazing process. Filler materials based on silver, copper, nickel, or aluminum are commonly used, and these fillers can be enriched with additives to enhance the strength, Fig. 1 — Example of images of different brazed coatings using tape technology.
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