Thermal spray deposits a nickel alloy coating onto a substrate by feeding powder or wire through a flame, arc, or plasma and projecting molten particles onto a prepared surface, where they flatten and bond. It builds wear-, corrosion-, and heat-resistant layers without heating the whole part, making it a go-to for repairing shafts, rolls, valve bodies, and large vessels — and for adding a thin nickel-alloy skin to a cheaper base metal. Hangbo supplies the nickel alloy wires and powders used as thermal spray feedstock, and the wrought forms that get coated.
Process choice — HVOF, plasma, arc
High-velocity oxy-fuel (HVOF) throws dense, low-porosity nickel-chrome and Inconel powders that resist erosion and cavitation — common on pump shafts, compressor seals, and turbine components. The high particle velocity packs the deposit into a coating with low oxide content and strong bond strength. Plasma spray handles higher-melting superalloys and ceramic-nickel blends for oxidation and hot-corrosion resistance, and is the route when the feedstock would not melt in an arc. Arc spray is faster and cheaper for large areas needing general corrosion cover, such as tank roofs and structural steel. Density, oxide content, and bond strength drive performance, so the process is chosen with the service in mind, much like picking an
overlay welding route for a fully dense layer.
Materials — what to spray
Inconel 625 and Hastelloy C-276 powders dominate corrosion service because their chemistry already resists chlorides and reducing acids; NiCr and NiCrBSi self-fluxing alloys are used for wear and rebuilding, where the boron and silicon let the coating fuse to a dense skin during a post-spray heat cycle. For sulfidation or high-temperature oxidation, nickel-chrome feedstock pairs with the same alloy logic used in
sulfidation-resistant selection. Feedstock chemistry must match the base part's environment, or the coating becomes the failure point rather than the protection.
Surface prep and sealing
Spray needs a rough, clean anchor profile — normally grit blasting with conditioned alumina — and an oxide-free substrate, because the bond is mechanical rather than metallurgical. Coatings are porous by nature, so a sealer or a fused top layer is often applied for immersed or chemical service to stop crevice attack at the pores. After coating, finish machining or grinding restores dimension and removes the as-sprayed roughness. The final surface still benefits from
passivation where the substrate is exposed at edges or through-coat defects.
Inspection and acceptance
Coating thickness is checked with magnetic, eddy-current, or cross-section methods against the drawing; bond strength is verified by pull-off or bend tests on first articles, and porosity is assessed from mounted samples. For wear surfaces, hardness is recorded, and for corrosion service a salt-spray or immersion check may be specified. These steps sit alongside the base-material checks described in
ultrasonic testing of the underlying wrought form.
Frequently Asked Questions
Thermal spray vs cladding — which for corrosion?
Cladding gives a fully dense, metallurgically bonded layer and wins for immersed corrosion; thermal spray is faster and cheaper for large or non-weldable parts but needs sealing. See the cladding guidance.
How thick can a thermal spray coating be?
Typically 0.1 to several mm per build; very thick deposits risk spalling, so rebuilds are staged with interim finishing.
Does thermal spray work on site?
Yes — portable HVOF and arc systems repair equipment in place, avoiding full teardown, which is why it is popular in process and power plants.
What nickel alloys spray best?
Inconel 625, Hastelloy C-276, and NiCrBSi self-fluxing powders are the workhorses; the choice follows the service environment.
Why Specify From Hangbo Alloy Group
As a dedicated nickel alloy manufacturer serving chemical processing, oil & gas, power generation, marine sectors, Hangbo Alloy Group supplies the grades discussed here across all standard product forms with full ASTM/ASME documentation and EN 10204 3.1 certification. Our material is specified for applications where corrosion resistance, high-temperature strength, and traceable quality are non-negotiable. See our production & testing facilities for more on how every heat is verified.
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