Surface engineering technology company, Hardide Coatings Ltd (Hardide plc: HDD: AIM) is developing a coating for gas turbine blades which will increase their durability and improve their resistance to erosion from hard particles and high speed water droplets; a combination of benefits not feasible from traditional coating methods including Titanium Nitride (TiN) and thermal spray Tungsten Carbide coatings.
Longer lasting turbine blades would offer substantial cost savings to power generation companies as blades are expensive components and replacement requires costly shutdown time. Maintaining optimum turbine performance for longer also saves fuel and reduces greenhouse emissions.
Neither TiN nor thermal spray coatings have proven totally successful in extending turbine blade life. Both give some improvement in part life but the effect of TiN is limited as it is very thin, usually no more than 4 microns in thickness, and thermal spray, while thicker, is not as resistant to high speed water droplet erosion.
Tests have been performed on the Hardide coating as applied to both steel and titanium substrates, two of the most commonly used blade materials, with very promising results. The liquid droplet erosion resistance of the Hardide coating was estimated to approach that of TiN and when combined with the ability to apply Hardide up to 25 times more thickly than TiN, the results are a significant development in the ability to achieve optimal performance for gas turbines.
Hardide coatings are produced using proprietary Chemical Vapour Deposition (CVD) technology which comprises of Tungsten Carbide nano-particles dispersed in a Tungsten metal matrix. The CVD coating technology is ideally suited to the uniform coating of complex shapes such as turbine blades. The unique structure and properties of the Hardide coatings combine ultra-high hardness with enhanced toughness, which are both important for erosion-resistance. Hardness is necessary to resist erosion from solid particles such as scale and soot dust from burning fuel or generated steam. Toughness and the ability to resist impacts are critical when the blades are hit by super-sonic water droplets which generate shock waves in the metal surface. The Hardide technology allows the hardness and toughness to be controlled over a uniquely wide range to achieve the optimal combination for the specific operating conditions of turbine blades e.g. the coating hardness can be varied from 400 Hv up to 3000 Hv depending on the application requirements.
Hardide Coatings manufactures its coatings from its facility in Bicester, Oxfordshire, UK. Hardide plc (AIM: HDD) is listed on the London Stock Exchange Alternative Investment Market.