Combating severe fluid erosion and corrosion of drill bits using thermal spray coatings

Abstract

Thermally sprayed tungsten carbide based coating offers an avenue to minimize severe fluid erosion, wear and corrosion encountered on drill bits and downhole tool assemblies used in mining, oil and gas drilling. The application of high rotary speeds and weights, presence of corrosive elements in the drilling muds, and high velocity mud with entrained cuttings subject these tools and drill bits to severe wear, erosion and corrosion and limit their service life. This paper describes the successful application of thermally sprayed coatings in minimizing the fluid erosion, abrasive wear and corrosion in three cone and polycrystalline diamond bits. The coating processes used are the as-deposited Super D-Gun coatings, spray and fuse with high powered laser and vacuum furnace coatings. The results of mud erosion test and field tests indicate that the detonation gun coated tungsten carbide coatings exhibit superior erosion resistance than all other coatings tested. The hard coatings can be applied on finished drill bit cones and polycrystalline diamond compact bits without damaging the cutters or substrate material.