Curtiss-Wright’s thermal spray coating service options produce cost-effective and high-performing coating that protects components from heat, wear, corrosion, fatigue, and oxidation.
Thermal spray coating can repair damaged and worn components to original specifications.
Thermal Spray Coating Process
Powder particles (typically 20 to 120 microns) are heated to a molten or semi-molten state and are propelled at the substrate at high temperature and velocity.
The molten particles form a “splat” on the surface, which contracts as it cools to form a strong bond with the surface.
Subsequent splats build up in layers to generate the required thickness and density.
Thermal Spray Coating Applications
Gas turbine engines
Intake section (cold)
Compression section (cold)
Combustion section (hot)
Autoclave Mixing Blades
Compressor blades and vanes
Combustion flame tubes
Power turbine discs
Rings and seals
Balls and Seats
Thermal Spray Coating – Benefits
There are a number of benefits in using thermal spray technology over more traditional coating methods and these include:
Versatility – choice of coatings include metals, alloys, ceramics and carbides among others.
Protection – against wear, corrosion, fatigue, oxidation and high temperatures depending on the coating used in the process.
Temperature Control – bulk substrate to 200°C or less avoiding any detrimental effects of heat on the substrate material properties.
Thickness Control – processes are easily controlled and can be used to restore the dimensions of a worn part or incorrectly machined component.
Robotic Animation – Complex shapes can be coated as the robotic automation allows for uniform coating of multifaceted parts.
Bond Strength – excellent bond strength which can withstand extreme mechanical loads and severe wear situations.
Thermal Spray Coating – Types
Combustion Wire Thermal Spray
HVOF – High-Velocity Oxygen Fuel
Arc Spraying – Electric Arc Wire
Combustion Powder Thermal Spray
Spray and Fuse
Thermal Spray Coating – CWST Expertise
Thermal Barrier Coatings can maximize turbine efficiency by allowing higher firing temperatures while reducing component thermal fatigue, warpage, oxidation and cracking. The combination of ceramic and super alloy constituents in GPX Thermal Barrier Coatings reflects heat back into the combustion gas path and insulates parts, effectively lowering their surface temperatures.
Wear due to vibration, friction, thermal gradients and pressure shortens the life of turbomachinery components. And if left unchecked, can cause expensive unscheduled outages. Coating that controls wear can prolong the life of critical turbomachinery parts by as much as 10 times. Anywhere metal touches metal is a candidate for Wear Control coatings.
Corrosion Control – Low Temperature
Corrosion of turbomachinery components costs operators billions of dollars every year through premature part failure and induced aerodynamic drag. Coatings for corrosion control can dramatically reduce corrosion damage while providing a smooth aerodynamic surface on compressor blades and stator assemblies. Tough CWST Coatings also provide resistance to erosion from dust and high velocity gases.
Corrosion Control – High Temperature
Turbine components exposed to corrosion at high temperatures (+ 1,000 °F) not only degrade faster than at lower temperatures, but also are subjected to cracking due to thermal fatigue and cycling. High Temperature Coatings are diffused into the substrate, creating a nearly impermeable oxide surface which can reduce scaling and cracks due to thermal cycling.
High temperature oxidation is a condition in gas turbines most responsible for premature failure of “hot section” components. As designers continue to raise turbine firing temperatures, super alloy components are nearing their theoretical limits. Oxidation Resistant Coatings are extending these limits by impeding oxygen penetration of the component surface while providing a sacrificial layer capable of protecting the part between overhauls.
Solid Particle Erosion Control
Solid particle erosion claims tons of steam turbine components every year and is most responsible for premature turbine failure. Often coupled with foreign object damage, solid particle erosion can be controlled effectively when temperature, impingement angle, velocity and size of erosion particles have been considered. Solid Particle Erosion Coatings are specifically designed and tested for this environment and have proven effective in extending the life of critical steam turbine parts.
In thermal spraying processes, feedstock material is fed into a thermal spray torch/plume induced by electrical (plasma or arc) or combustion means, then heated, melted and impacted at a high velocity on the component surfaces to produce well-adhered layer deposits.
How long does thermal spray coating take to apply?
Thermal spray is highly efficient process to apply a coating at acceptable high deposition rate. The process time depends on multiple factors such coating area and thickness, type of coating and process efficiency, varying from a few minutes to a few hours.
What items can be thermal sprayed?
Many items can be thermal sprayed, including components of gas, turbine engines, complex machinery, and valves, as well as smaller individual items of the components such as rings, seals, seats, and discs.
Which processes are most commonly Used in thermal spray?
For the advanced thermal spray technologies, plasma spray is typically used for ceramic coatings, and high velocity oxy-fuel spray for alloy and carbide coatings
Which forms of materials are commonly used in this Process?
Typical feedstock materials are in forms of solid powders and wires. The latest processes such as solution or suspension plasma spray, can use liquid precursors and suspension slurries as feedstock
Compared to Other Coating Technologies, What Are Thermal Spray’s Advantages?
Thermal spray technologies are considered as “green” technology, and are applied as alternatives to some chemical plating coatings, for example. Unlike many paints produce/contain volatile organics which can environmental issues, but will not present in the thermal spray techniques. Many materials ranging from polymers, plastics, light metals, superalloys, refractory alloys, carbides, composites and ceramics are safely and readily deposited through this process. In addition, thermal spray is applicable for depositions onto the components with different dimensions (small to large) and configuration (OD to ID)
What is the bonding mechanism and the maximum tensile bond strength in thermal spray?
Non-metallurgical bonding is typical for a thermal spray coating. Coating bonding is created on a roughened surface primarily by the mechanism of mechanical interlocking. For some coating systems, the maximum bond strength by tensile pulling test can reach above 10,000 Psi
How is operated thermal spray?
It can be operated manually or by automatic robot armed spray gun, normally in a sound-proof thermal spray booth. If necessary, thermal spray can also operate on site. Coating thickness is built in multiple spray passes/cycles
Which industry is applied thermal spray?
Thermal spray processes are widely used in many industry sectors, including aerospace, mechanical, marine, and automotive applications. They are also used for electronics, biomedical as well as several other applications.
What are key criteria for evaluation of thermal spray coating?
Several criteria are used to evaluate the quality of the coatings, such as bond strength, porosity, oxidation, hardness, and roughness.
What are typical thickness for thermal spray coating?
Typical coating thickness from a few mils to 20 mils. The coating’s thickness can be as small as 20 microns, or it can be several millimeters thick.