This work introduces a hybrid spray-and-fuse process and a modified CoCrMoC (Stellite) alloy that significantly expand the manufacturing window for wear-resistant coatings. The Co-based alloy was produced by adding Ni, B, and Si to Stellite 720 to lower its melting points and expand its melting range thereby improving the sprayability and fusibility of the material. The modified alloy was deposited on Inconel 718 balls and 1 in. diameter coupons by HVOF spraying and coating samples were sinter fused at high temperatures followed by furnace cooling. The processes used are described and test results are presented, showing that thick, metallurgically bonded coatings were achieved with high hardness and excellent wear and corrosion resistance.

Three different oxides of CrO 2 -TiO 2 , Al 2 O 3 and Al 2 O 3 -TiO 2 were plasma-sprayed on Ti substrate to evaluate the crystal structure and the corrosion properties of the coatings. No phase change of the coatings after corrosion test in 0.5 M H 2 SO 4 solution at 25°C was found regardless of the presence of the NiCoCrAlY bond layer. Electrochemical measurements and SEM results revealed that the single coatings without the bond layer were always effective against corrosion resistance due to lower current density within the passive region. Pitting corrosion of the surface was observed for the Al 2 O 3 coating. It can be concluded that the Al 2 O 3 -TiO 2 coating without the bond layer may be the best oxide among the oxides investigated due to low porosity (5.4%), smooth surface roughness (4.5 m), low current density (6.3×10-8 A/cm 2 ) in the passive region, low corrosion potential (Ecorr, -0.55 V) and no pitting corrosion.

Replacement of Electrolytic Hard Chrome plating (EHC) using High Velocity Oxygen Fuel (HVOF) thermal spray processes to apply dense, wear and corrosion resistant coatings has been identified as a significant goal for the advancement and growth of the thermal spray industry for several years. This paper will provide some details of the development and production implementation of a WC-Co-Cr coating to be used as an alternative to EHC. WC-Co-Cr has been demonstrated in most situations to be superior to the wear performance of EHC with respect to providing functionality in aircraft landing gear hydraulic seal and bearing service. The developed coating is produced via the HVOF process using natural gas as fuel. EHC alternatives using WC-Co-Cr HVOF coatings require significant development prior to implementation into practice. Suitable wear, corrosion and lack of fatigue debit are examples of a few critical properties of coatings for use in landing gear applications. In addition a brief description of the production implementation of a turnkey spray cell for the coating of landing gears will be provided in this paper.

This work evaluates HVOF sprayed cermet coatings as an alternative to galvanic hard chrome plating for applications requiring corrosion and wear protection. WC-10Co-4Cr layers were deposited on different types of steel using commercially available HVOF systems. The coatings were then assessed based on their friction, wear, adhesion, and corrosion behaviors, which are shown to compare favorably with those achieved using a commercial hard chrome plating system. The paper also sheds light on how salt spray attacks protective surface layers at the edges, causing corrosion that propagates along the interface with the substrate. When coating edges were protected, exposure to salt spray atmospheres did not jeopardize the bond strength of any (cermet or chrome) coating tested. Paper includes a German-language abstract.