Antiwear and anticorrosion consumiveils characterization produced especially for arc spray process to coat offshore platforms tips risers

Abstract

Through the thermal spray process barriers of layers forms materials with high, wear and corrosion resistance are applied, involving high hardness particles. The tips, manufactured in AISI 4130 steel and 17-4 PH Stanley steel, under assembly scratch out risks and sea water corrosion on OFF SHORE platforms, have been protected with chemical nickel and thermal aspersion using WC-Co, WC-Co-Cr, Cr3C2-NiCr, (WC-12Co) + NiCrFeSiBC alloys and a Ni autofluxant alloy, using two HVOF systems; the results had been interesting, however the layers still presents small crack deep into the scratch. The objetive of this work is to present results of the arc spray layers using Ni base alloys with B and Si additions and other wires using Ni base alloys rich in Cr, Si and FTC. Were evaluated the microstructures (carbides and porosity dispersion degree), the wear and stress resistance, hardness and covering fusing degree. The analyses shows a matrix layer with hardness varying between 350 and 600 HV, and fine tungsten carbides particles, concentrated as triturated for impact (~1µm), with hardness over 1200HV, as well as scarce coarser particles (~50 µm), not broken up, with hardness between 2000 and 2800 HV. The matrix hardness lower than that sprayed with the HVOF process, assures a better ductility, it allows assuring the crack absence deep into the scratch during the cratch out test. The best performance to waste was found in the wire with bigger amount of Cr that gives as result a corrosion resistance.

The other studied wires present a good potential with sights to its use in riser tips covering, being the preheating a factor of sprayed layers improvement.