Master Flo

“The focus was on using Hardide-T on our HPHT choke valves that face temperatures greater than 350oF, pressure over 15,000psi, or both. Hardide Coatings worked with us to provide a solution that met all our criteria, and to fine tune the manufacturing process to achieve the specific surface finish and geometrical tolerance required for these parts.”

Everett Marshall, Master Flo


Headquartered in Canada, Master Flo Valve Inc. provides surface and subsea flow management solutions for the global oil and gas industry. The company’s customers rely on its choke valves, control valves and actuation, along with its expertise and worldwide support to lower cost and optimize production through reliable flow for the life of their fields.


Master Flo needed a new coating solution for its choke valve stem assemblies. The coating had to be rated to temperatures as high as 400oF — a requirement which eliminated all standard coating options — and be capable of withstanding operating pressures up to 20,000psi.

In addition, resistance to corrosion, erosion and wear were all critical. The choke valves utilize a metal-to-metal primary stem seal system, so in order to maintain sealability, the surface finish on the stems have to withstand the wear of hundreds of choke cycles in subsea environments such as single or multiphase production, as well as water, chemical or gas injection.


Working together, Hardide Coatings and Master Flo engineered a solution and the Hardide-T chemical vapor deposition (CVD) coating is now used to hardface stems on the Master Flo P4-15k and P4-20K subsea bolted bonnet choke valves.

Fully qualified to API 6A, API 17D PR2 / PR3 requirements, and designed per API 17TR8 requirements, the subsea choke valves using the Hardide-T coating are rated to depths of 10,000ft for temperatures from -20oF to 400oF and pressure of 15,000psi for the P4-15k and 20,000psi for the P4-20K. The CVD coating is also used on an application for a capping stack designed to be deployed in a blow-out situation.

Everett Marshall, Engineering Subsea Team Lead, Master Flo said: “Any subsea choke valve will need to contend with corrosion issues related to H2S exposure, a wide range of production fluids, acid injection fluids, sea water and sometimes drilling fluids. Because of the testing already carried out, Hardide-T was a good fit. Our HPHT subsea chokes with the Hardide-T coated stems are currently in use in the Gulf of Mexico and performing as expected.”