Hardfacing has been given a tungsten carbide boost thanks to chemical vapor deposition technology developed in Russia. Elaine Maslin explains.
Hardide reactor loading to perform the CVD process. Photos from Hardide Coatings.
Coating technology developed in Russia using chemical vapor deposition (CVD) to coat thermally stable polycrystalline (TSP) diamonds with protective tungsten carbide has been developed for use on drilling inserts on downhole tools requiring gauge protection.
The coating, commercialized by Hardide Coatings in the UK, could be used on tool sections such as stabilizers and bent housings, as well as on logging-while-drilling tools, rotary steerable tools and downhole motor bearings.
The CVD technology, which was presented at this year’s ITF Technology Showcase in Aberdeen, is used create Hardide’s Hardide-D coating, which was designed to be used as hardfacing.
The CVD process is used to evenly apply a gaseous mixture of tungsten carbide heated to 500°C to materials to create a non-porous, abrasion and corrosion-resistant coating. The coated diamonds can then be brazed to the drilling tool.
“A TSP diamond is strong, but it has weaknesses that restrict its use as a hard facing,” says Dr Yuri Zhuk, technical director, at Oxfordshire-based Hardide. Its poor wettability makes it difficult to bond with metal [i.e. brazing] and it also suffers from graphitization at high temperatures, which are used during its application to metal surfaces.
“By adding a Hardide-D coating, these limitations can be overcome,” he says. The tungsten and carbide in vapor form crystalizes on the surface of the diamond evenly, creating a chemical bond, instead of mechanical. This then creates a pore-free surface that is resistant to high temperatures, thus preventing oxidization/graphitization, and to which metal can be bonded.
Hardide coated and uncoated TSPs.
In tests, a surface coated with Hardide-D TSP diamonds was applied at 155rpm rotation, with 250kg load and 2.5Hz impacts, and showed limited wear.
“What we have developed enables diamonds to be used as a hard facing and allows them to be bonded with brazing or metal bonding,” Zhuk says. “It enables a new generation of TSP diamond for hard facing.”
The coating can also be used for different applications within drilling, such as on reamers and drilling heads, but also elsewhere in the oil and gas industry and across other industries.
England-based Cutting & Wear is already using Hardide-D on its TSP diamond hardfacing material, marketed as TSP Xtreme inserts, which the company says gives 200-times improvement over tungsten carbide inserts, extending the life of drilling tools.
Hardide Coatings recently announced its opening a new US$7 million production facility in Martinsville, Virginia. The plant will service existing and new customers in the oil, gas, aerospace, flow control and advanced engineering markets. The facility is expected to be operational in 4Q 2015.
Hardide has also recently invested in a 50% increase in capacity at its UK production site in Bicester, Oxfordshire.