Nanotechnology applied to powder metallurgy for the metal injection moulding (MIM) process has made significant advances in recent years and is in a rapidly evolving stage, with research underway to broaden its applications and optimise each stage of the MIM process.
Current research is focused on obtaining MIM products with better properties, the development of new materials and the optimisation of manufacturing processes.
Nanotechnology for the improvement of mechanical properties
1. Increased strength and hardness
The addition of certain nanoparticles in the metal powders of feedstock formulations significantly increases the strength and hardness of components manufactured by MIM. These nanoparticles act as barriers to the movement of dislocations in the metal’s crystalline structure, resulting in dispersion hardening. For example, the addition of yttrium oxide nanoparticles to nickel alloys can increase their tensile strength by up to 30%.
2. Improved fatigue resistance
The addition of nanoparticles dispersed in the metal matrix act as obstacles to crack propagation, thus improving fatigue resistance. This is particularly important in applications where components are subject to cyclic loading. Recent studies have shown that the addition of titanium carbide (TiC) nanoparticles to aluminium alloys can increase fatigue life by up to 50%.
3. Higher density and reduced porosity
The use of metal powders with nano-sized particle size distributions allows for better compaction during the MIM process. This results in a higher final density of the sintered parts and a significant reduction in porosity. Relative densities in excess of 99% have been achieved in 316L stainless steel components made from nanostructured powders.
Nanotechnology for developing new materials
1. Superalloys with ceramic nanoparticles
The addition of ceramic nanoparticles such as titanium carbide (TiC) or boron nitride (BN) to nickel or cobalt-based superalloys has significantly improved their high-temperature strength and mechanical stability. These nanostructured superalloys are used in gas turbine and aircraft engine components, where they can operate at temperatures up to 100°C higher than conventional alloys.
2. Self-lubricating materials
The incorporation of graphene or molybdenum disulphide (MoS2) nanoparticles into the metal matrix has allowed the development of materials with self-lubricating properties. These materials significantly reduce friction and wear in applications where conventional lubrication is difficult or impossible. For example, bearings made from these nanostructured alloys have shown a reduction in the coefficient of friction of up to 40% compared to conventional materials.
3. Nanostructured coatings
Nanotechnology has enabled the development of ultra-thin, highly adherent protective coatings for parts manufactured using MIM. These coatings, which can be as thin as a few nanometres, significantly improve the corrosion and wear resistance of components. One example is the use of nanostructured titanium nitride (TiN) coatings on cutting tools, which can increase tool life by up to 300%.
Optimisation of the MIM production process
1. New binders at the nano-scale
Tests are underway to develop binders incorporating polymeric or ceramic nanoparticles to improve the rheological properties of the mixture during injection. These new binders are designed for better flowability at lower temperatures, which reduces thermal stress on the metal powders and improves the final quality of the parts. In addition, these nanostructured binders facilitate subsequent removal at the debinding stage, reducing both processing times and the risk of defects.
2. Better sintering control
Nanotechnology is making it possible to have increasingly precise control of the sintering process. The use of nanostructured metal powders and the addition of sintering activator nanoparticles have in some tests allowed sintering temperatures to be reduced by up to 200°C and processing times to be reduced by more than 50%. This not only improves the energy efficiency of the process, but also reduces the formation of unwanted phases and excessive grain growth.
3. Increased dimensional precision
The use of metal powders with nano-sized particle size distributions has made it possible to obtain components with tighter tolerances. Shrinkage during sintering is more uniform and predictable, resulting in better dimensional accuracy. Tolerances of up to ±0.1% have been achieved on complex components, which was previously difficult to achieve with the conventional MIM process.
Nanotechnology and Advanced Manufacturing: state of the art and trends
Integration with additive manufacturing
The combination of nanotechnology, powder metallurgy and additive manufacturing is enabling the production of components with complex geometries and customised properties. For example, 3D printing techniques are being developed that use nanostructured metal powders to manufacture components with gradients of properties, where the composition and microstructure vary in a controlled way throughout the part. This opens up new possibilities in the design of optimised components for specific applications.
Sustainability and energy efficiency
Innovations in sintering at lower temperatures, made possible by nanotechnology, have made it possible to reduce the energy consumption of the MIM process by up to 30%. In addition, the reduction of processing times further contributes to the overall energy efficiency of the process.
Recycling of metal powders
Advanced techniques have been developed for the recovery and reuse of nanostructured metal powders. These methods, which include nano-scale separation and purification processes, allow up to 95% of unused powders to be recycled, significantly reducing environmental impact and production costs.
Nanotechnology and powder metallurgy: research in progress
1. Development of superalloys for aerospace applications
Current research focuses on the development of nanostructured superalloys with improved thermal and mechanical fatigue resistance. New combinations of reinforcing elements and nanoparticles are being explored to create alloys capable of operating at temperatures above 1200°C in highly corrosive environments.
2. Biomedical applications
Nanotechnology is enabling the development of metallic implants with improved biocompatibility and osseointegration properties. Nanostructured titanium alloys with bioactive surfaces that promote bone growth and reduce the risk of rejection are being investigated. In addition, implants with antibacterial properties are being developed by incorporating silver nanoparticles.
3. Multifunctional nanocomposites
Research into multifunctional nanocomposites seeks to integrate electrical, magnetic and mechanical properties in a single material. For example, nanostructured alloys combining high mechanical strength with electromagnetic shielding properties are being developed for electronics and defence applications.
These advances and trends in nanotechnology applied to the MIM process are continually expanding the frontiers of what is possible in the manufacture of advanced metal components, promising new solutions to the technological challenges of the future.
