Brazing Technologies for Ceramic and Composite Materials

Brazing is a versatile high‐temperature joining technique in which a molten filler metal wets and bonds to substrates without melting the base materials. It offers unique advantages for ceramics and composites, including the ability to join dissimilar materials such as oxide ceramics, carbides and carbon‐fibre‐reinforced composites to metals, while preserving the integrity of the parent phases. Critical challenges arise from poor wettability of oxide surfaces, thermal expansion mismatches and the formation of brittle intermetallics or reaction layers. Contemporary strategies address these issues through the use of active filler alloys that contain reactive elements (for example Ti or Zr), engineered interlayers, laser and electric field‐assisted processes and tailored surface topographies. These advances underpin applications in aerospace and defence (SiC‐based composites), energy systems (solid oxide fuel cells and fusion reactors), electronics packaging and biomedical implants, where high joint strength, thermal and electrical conductivity and long‐term reliability are paramount.

Research from Nature Portfolio

Recent studies have demonstrated that femtosecond laser surface machining of yttria-stabilised zirconia substrates creates a rumpled interface that redistributes residual stresses within the reaction layer. Image-based modelling reveals that surface texturing converts detrimental tensile stresses into compressive zones at the groove boundaries, inhibiting crack initiation and propagation. This approach has yielded shear strengths approaching 150 MPa, almost double those of conventionally prepared flat interfaces, thereby marking a step-change in joint reliability for ceramic-to-metal brazed assemblies.

Brazing Technologies for Ceramic and Composite Materials publication trend

The graph below shows the total number of articles in brazing technologies for ceramic and composite materials across all publications each year (not limited to Nature Index journals).

Technical terms

Brazing: A joining process in which a filler metal is melted above its liquidus temperature to wet and bond substrates without melting the base materials.

Active filler metal: A brazing alloy containing reactive elements (e.g. Ti or Zr) that form chemical bonds with ceramic surfaces to improve wettability and adhesion.

Interfacial microstructure: The arrangement of reaction products and phases at the joint interface that governs mechanical strength and thermal stability.

Spark plasma sintering (FAST): An electric field- and pressure-assisted technique for rapid sintering or joining, utilising pulsed currents to generate heat internally and achieve densification.

Residual stress: Internal stresses remaining in a joint after cooling, arising from differences in thermal expansion between joined materials.

Wetting: The ability of a liquid filler metal to spread across and adhere to a substrate surface, critical for forming a continuous bond.

References

1. Understanding the Effect of Surface Machining on the YSZ/Ti6Al4V Joint via Image Based Modelling. Scientific Reports (2019).
2. Brazing filler metals. International Materials Reviews (2019).
3. Near-seamless joining of Cf/SiC composites using Y3Si2C2 via electric field-assisted sintering technique. Journal of Advanced Ceramics (2022).
4. Microstructure Evolution and Mechanical Properties of Titanium/Alumina Brazed Joints for Medical Implants. Metals (2019).