Polishing HVOF WC-Co slab gate valve surfaces

Finishing Tungsten Carbide Cobalt HVOF Surfaces

Tungsten Carbide Cobalt (WC-Co) coatings deposited by High Velocity Oxy-Fuel (HVOF) processes, produce very dense near zero porosity, and wear resistant surfaces.  These characteristics make WC-Co coatings an ideal surface for high pressure slab gate valves to increase the strength and reliability for future savings in repair costs.

The basic surface requirements for these high pressure oil and gas slab gate valves are:WC-Co coating

  • Flat
  • Smooth
  • Scratch Free
  • Parallel

As coated, the WC-Co surfaces are not flat, not smooth, nor parallel.

Traditionally, valve manufacturing process and surface finishing have been accomplished in the following manner:

  • Machine new or reclaim parts
  • HVOF WC-Co coating
  • Grinding 0.5 hours or more per side
  • Lapping 10 minutes up to hours per side depending on the quality of the grinding
  • Polishing with diamond paste or spray 10 minutes up to hours per side, varying results on scratching

Accepted industry specifications are:

  • Flatness: 4 light bands or less
  • Surface Finish: Less than 4u” Ra (0.1um), up to 8u” Ra (0.2um)
  • Scratches: Cosmetic (ugly scratches not acceptable)
  • Parallelism: 0.0005” (12.5um) maximum

Now Valley Design can provide much better results.  Our process yields superior quality surfaces in as few as 5 minutes!  Valley Design’s specifications are:

  • Flatness: 1-2 light bands, depending on the geometry
  • Surface Finish: 1-2u” Ra (0.025 – 0.050um)
  • Scratches: Virtually non-existent (not measurable)
  • Parallelism: 0.0005” (12.5um), and even to 0.0002” (5um) if needed

Further benefits of the Valley Design lapping and polishing process:

  • Scratch free and flatter surfaces than produced by traditional methods enhance the performance of the valve interface to improve and hold higher oil and gas pressures
  • Improved surface finish is a must for wear resistance
  • Parallelism for ease of operation and longer valve life
  • Time savings – from a good quality grind, our polishing process yields a high quality surface in as little as 5-10 minutes

How can a valve manufacturer or user benefit from Valley Design’s 40 years experience in surface finishing?

  • Valley Design does not machine valves
  • Valley Design does not HVOF thermal spray coat
  • Valley Design DOES grind, lap and polish to the best specifications in the industry

Your parts can be finished at our facility in Shirley, Massachusetts, or we also offer consulting services, process transfer or complete turn-key solutions.  We can set up your company’s in-house HVOF WC-Co valve finishing capability in as little as 30 – 60 days.

Please send inquiries to:
Gunars Indars, Technical Director
Valley Design Corp.
Email: gunars@valleydesign.com
Telephone: 978.425.3030
Cell:  978.501.7905


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Valley Design East
Phoenix Park Business Center
2 Shaker Road, Bldg. E-001
Shirley, MA 01464
Phone: 978.425.3030
Fax: 978.425.3031

Valley Design
Santa Cruz, CA 95060 
Phone: 831.420.0595 
Fax: 831.420.0592

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