Joining and processing technologies used for ‘The Cutting Edge’
The display piece provided TWI with an opportunity to showcase a number of different joining techniques and material processing capabilities
Surfi-Sculpt (Electron Beam) – This novel power beam materials processing technology uses either a laser or an electron beam to create features across a surface. This results in a textured surface with an array of protrusions above the original surface and corresponding intrusions or cavities in the substrate. This technology can be applied to metals, polymers, ceramics and glasses to create surface features for specific applications in just a few seconds per square centimetre.
Rotary Friction Welding – This solid state joining process, also known as spin welding, involves spinning one part to be joined against a stationary part to create high friction heat between the two workpieces. Once the friction heat has been generated, the rotational force is removed and the two pieces are pressed together as they cool. This fast, inexpensive process is generally used to join cylindrical or circular parts but is also a good method for joining dissimilar materials. This particular segment was kindly provided by TWI Member Company, KUKA Systems UK Ltd.
Direct Metal Deposition – This additive manufacturing technology uses a laser to melt metallic powder using a feed nozzle to propel the powder into a laser beam. The laser then fuses the powder layer-by-layer to create a solid metal object. This technology can be used with a range of metallic materials, including steel, aluminium, titanium, cobalt and copper.
Surfacing – Surfacing, also known as surface engineering, describes the process of altering the characteristics of a material to improve the surface properties. This can be done in a number of ways, ranging from traditional electroplating to weld overlaying, thermal spraying, thermochemical treatments and more modern methods such as physical vapour deposition (PVD), chemical vapour deposition (CVD), ion-implantation, laser surface modification, plasma thermochemical diffusion treatments and cold spraying.
Linear Friction Welding – A solid-state joining process pioneered by TWI, this welding technique involves pushing two parts together – one of which is oscillated rapidly. The oscillation creates frictional heat on the contact surfaces of the parts, which soften, but do not melt. The oscillation is then stopped and the parts are pushed and bonded together to form a forged joint. This technique is not only fast (4-7 seconds) and highly consistent, but requires very little preparation of the surfaces to be joined as any imperfections are removed as flash. With no need for consumables and no harmful fumes being produced, this process avoids the potential issues associated with solidification, such as segregation and porosity.
Manual (Arc) Welding – Manual metal arc welding is one of the most versatile joining processes and is suitable for welding both ferrous and non-ferrous materials over a range of thicknesses and positions. Easy to use and economical, this was one of the most common of the arc welding processes, although this has now been surpassed by MIG/MAG welding processes.
Friction Stir Welding – A method invented by TWI, this solid-state process is suitable for joining difficult-to-weld materials like aluminium. Commonly used for the manufacture of lightweight transport applications, friction stir welding uses a rotating tool between two clamped workpieces. The rotating tool produces heat between the parts as it moves along the joint line to create high quality, high-strength joints with low distortion in a range of positions and thicknesses. This process does not suffer many of the defects associated with fusion joining methods, such as significant shrinkage, solidification cracking and porosity.
Brazing – This process is suitable for a range of industry sectors and applications and is particularly suitable for joining dissimilar materials. Unlike with welding, this is not a fusion process and as such the parent materials do not need to be melted. This makes brazing ideal for joining metals and ceramics in both similar and dissimilar combinations. Brazing also maintains near-parent properties, has minimal effect on the shape of parts, allows for reworking and requires no post-finishing.
Electron Beam – TWI has been active in the development of electron beam technology since the 1960s. This technology is widely used in industry sectors such as aerospace, automotive, defence, electronics packaging, medical, oil and gas, power, space and engineering and fabrication. Used in a variety of processes, electron beam can be used for additive and non-additive manufacturing, and both in and out of vacuum chamber applications.
Laser Processes – The display piece incorporated a range of laser processes, including laser welding, laser etching, and robotic welding. Laser welding uses a lower heat input than arc welding processes, allowing for the joining of components requiring minimal thermal distortion, or materials favouring a low heat input. With robotic automation providing a repetitive and reliable method, laser welding is a versatile fusion process with a great many industrial applications.
Non-Destructive Testing – Non-destructive testing is use across all industry sectors to inspect both metallic and non-metallic components and structures. It can be undertaken during production, in post-production, in service, or following repair. An integral part of failure investigations and risk-based inspections, non-destructive testing takes the form of various techniques and applications according to industry requirements.