Energy Technology Services Company

The nanostructured Hardide-T coating is six times more wear resistant than HVOF WC-83% / Co-17%


Our customer is a leading energy technology company that provides solutions to oilfield and industrial customers worldwide.

The company offers a comprehensive portfolio of subsea solutions, systems and products including the design and manufacture of subsea chokes needed to ensure reliable and safe reservoir performance. The subsea choke valve is the primary flow control valve in a subsea system for both production and injection applications. Choke valves are used for wellhead production and injection flow and pressure control to maintain optimum production output of a subsea field. Our customer has supplied more than 2,000 subsea choke valves offering modular configuration options suitable for shallow to deepwater use. The ‘plug and cage’ design choke uses the plug as the controlling element which runs up and down a ported lower guide to restrict the flow the plug in-line during operation. Our customer’s choke valves routinely operate in severe service conditions e.g. with process fluid wetted with potential high H2S or CO2 or sandy, corrosive environments that can range from 155°C to -46°C. 


Our customer wanted a wear, erosion and corrosion resistant coating for the inner diameter (ID) of their range of upper guides. The guides are manufactured in Inconel 718, a standard material for subsea valve applications and could potentially suffer from ID wear during operation. High Velocity Oxygen Fuel (HVOF) applied tungsten carbide (WC) is a standard coating for our customer but the size of the nozzle used to apply this thermal spray coating restricts the size of ID and geometry of parts that can be coated. We worked with our customer to develop a coating solution suitable for the full range of sizes of upper guide choke parts.

Subsea Choke Valves


The Hardide chemical vapour deposition (CVD) coating process means that the coating can be applied to internal surfaces, complex geometries or parts with a small ID that prohibit spray gun application. Under abrasion testing ASTM G65, the nanostructured Hardide-T coating is six times more wear resistant than HVOF WC-83% / Co-17%.

Testing of the coated parts was as per API 17D 2nd Edition. The choke underwent 500 cycles with the piston/scraper rings running full 4” of travel 1000 times on the Hardide-coated surface with 20 cycles at 155°C and 20 at -46°C.

The Hardide-T coating is now designed on four sizes of upper guides that are in use in subsea trees in the UK North Sea and Norwegian North Sea, and in Asian Pacific and Sub-Saharan Africa subsea projects.