Refractory metals are a group of five metals: Tungsten (W), Molybdenum (Mo), Niobium (Nb), Tantalum (Ta), and Rhenium (Re). They all have very high melting points above 2000°C. Even at extreme temperatures, they keep their shape well (resist bending or changing shape), stay chemically stable, and remain strong. For example, tungsten melts at 3422°C (the highest of any metal) and is over twice as strong as iron at room temperature. Rhenium can evaporate easily in air, so it needs protection in an inert gas to keep its properties. Because of their special abilities, refractory metals are essential materials for high-temperature industries.
Aerospace: Niobium alloy C103 (with Hafnium and Titanium) is used to make thin-walled parts for rocket engines using laser-based 3D printing (DED-LP). NASA research shows that after special heat treatments, this alloy can last over 50,000 stress cycles. However, parts printed in a vertical direction can sometimes crack between layers.
Medical: Tantalum is the top choice for bone implants because it doesn't react with body tissues. 3D-printed porous tantalum parts have tiny holes (20-80 micrometers) that help bone cells grow into them. German companies use Selective Laser Sintering (SLS) to 3D print custom skull repair plates directly, saving extra processing steps.
Better Powders: The America Makes institute and 6K Additive are developing improved C103 Niobium alloy powder. Using Powder Bed Fusion (PBF) and DED printing aims to use over 95% of the material. A Nickel-Silicon (Ni-Si) powder was treated with a plasma process that makes it flow better. This makes 3D printed coatings 30% harder, but high silicon can cause tiny cracks due to leftover stress.
New Sintering: FCT Systems (Germany) makes commercial microwave ovens for sintering large parts (up to 500mm). Tungsten powder processed this way becomes 50% stronger (reaching 1200 MPa) than with old methods. This is now used to mass-produce satellite thruster nozzles.
Precious Metals Recycling: The Plasma Rotating Electrode Process (PREP) recycles titanium alloy waste into powder with very low oxygen (0.05%), costing 40% less than new powder. Samsung (Korea) prints 5G antenna grids using nano silver paste. This paste needs much lower heat to set (150°C) and has very low electrical resistance (2.5μΩ·cm), opening new uses for refractory metals in low-temperature electronics.
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