Thermal Spraying Process
The process shall be of type High Velocity Oxygen Fuel (HVOF).

Coating Composition
The coating shall be of type 86% tungsten carbide (WC) and a metallic binder consisting of 10% Co and 4% Cr. Other coating compositions are subject to agreement with the Company.

Coating Thickness
The coating shall be minimum 0.2 mm after grinding and lapping.

Pre-treatment
The components shall be cleaned for removal of oil by a cleaning agent (acetone or similar) before grit blasting. The components shall be heated to a temperature well above dew point and be immediately grit blasted in warm condition. A suitable temperature is often 60-90°C. Any dust or particles shall be removed before spraying.

Thermal spraying
The component shall be coated immediately after the heating and grit blasting while the component still is at a temperature well above the dew point. All seating areas of valves shall be coated as a minimum. However, for ball valves, the complete spherical part of the ball shall be coated. For gate valves all surfaces sliding against the seats during valve operation shall be coated.

All thermal spraying shall be carried out under optimal conditions and accordance with established and qualified procedures which ensure that the coating on all areas fulfil the specified requiremets.

Sealing
All coated surfaces shall be sealed after spraying. The type of sealer shall be specified.

Finishing
The coating shall be finished by grinding and lapping to a fine and smooth surface resulting in good sealing properties and a low coefficient of friction.

Testing
Bending test shall be carried out once for each batch: The batch is defined as all equal components sprayed with the same spraying equipment, with the

same batch of powder and sprayed the same day. Three test coupons, with the size approximately 20 x 100 x 1.5 mm shall be coated together with the

first valve component in the batch. The coating thickness shall be the same as for the component.

The test coupons shall be bent over a mandrell with a diameter of 15 mm. The coupons shall be visually inspected. No spalling is acceptable. However, due to the low ductility of this type of coating cracks are acceptable.

Hardness testing and microscopic examination shall be made on the bend test coupons or on separate specimens coated together at the same time. The hardness shall be minimum 1000 HV10.

Porosity
One piece of the bending test coupons shall be prepared for cross section metallographic examination. The porosity shall be established by microscopic examination. The porosity shall be less than 1 % by volume.