SVCC COATINGS

[mo_verify_phone]

Characteristic of SVCC Process

High velocity thermal spray systems such as the High Velocity Oxy-Fuel (HVOF) and supersonic velocity continuous combustion (SVCC) systems have been successfully utilized for in-situ applications for the past decade. A supersonic velocity thermal spray process is one where the material is atomized and / or accelerated under supersonic gas velocities (greater than the speed of sound). For this reason, the energy of the gas stream is focused directly on the material to be sprayed, producing a coating that has low permeability, and has a homogeneous coating structure than a low velocity coating. Further the bonding strength is excellent.

SVCC coating permeability and its importance

Permeability of a correctly selected and applied coating, in a corrosion environment, is the primary characteristic that determines the coatings useful life. If the coating is permeated at a rapid rate by corrosive media, and if the media reacts with the substrate underneath the coating, the bond of the coating to the substrate will be degraded. This substrate degradation may result in the coating spalling from the surface. SVCC coatings have very low permeability due to lowest porosity and special sealing process utilized.

In corrosion applications, a finer more homogenous coating will be less likely to suffer metallurgical segregation effects.Segregation occurs to a larger extent in low velocity coatings where particles are larger, and low alloy, heavily oxidized layers form around each spray particle. Thus low velocity coatings will corrode internally at a much higher rate, leading to premature coating failure.

Benefits of SVCC technology coatings

• Repairability of coatings is key factor for coating installations which is possible with SVCC process.
• Selective alloying can enhance the reparability of coatings and therefore, offer a viable solution for protection of low-alloy materials and the same is established in SVCC process.
• SVCC has in some grades alloy type with a binder phase with special composition to combat corrosion and erosion. The material maintains its strength at high temperature and resist brittle fracture.
• SVCC provides erosion/corrosion protection superior to technologies traditionalloy used in Boiler Tubes. It exceeds the erosion/corrosion and thermal cycling resistance of carbon steels/SA 210 Gr, thermal sprays, HVOF’s and ceramics.
• Corrosion Resistance : Some grade of SVCC are based on master alloy (Nickel, Chromium, Moly etc.) It is vastly superior to carbon steel/SA 210 Gr.
• Coatings can be easily repaired.
• Super Alloy Barrier : SVCC sprayed special coatings achieves almost fused, homogeneous master alloy barrier, unlike coatings, sprays and ceramics which adhere with mechanical bonds.
• Coatings thickness : SVCC system provides a 500 μ to 5 mm thick alloy barrier compared to typical 250-500 μ of metallized coatings / HVOF coating for some special grades of material.
• Very fast application so shut down period is not increased.
• Life achieved is minimum more than two times against carbon steel which sees extreme corrosion and erosion when exposed to high temperature of boiler tubes.
• Coatings can have differential thickness depending on different wear rates at
  different locations.
• No combustible gases required at site hence safe for the plant.
• Since the chance of selection of special alloys is available, it can be sprayed according to the particular environment on the boiler application.