Thermal Spray is a cost-effective means to enhance the strength of substrates or repair worn components.
Thermal Spray Coatings
Thermal sprayed coatings are extremely effective at increasing the component life and value, decreasing machinery down-time, and improving performance in a wide variety of applications. Thermal spray coatings can be engineered using most metals, carbides, ceramics, and plastics to create a coating with the optimum properties for your application. Thermal spray coatings can be applied to a broad range of materials, from metals to composite materials.
These are some of the industries achieving new and better results with thermal spray coatings.
- Oil & Gas
- Food Processing
Types of Thermal Spray Coatings
Plasma spray is the most versatile of the thermal spray processes, applicable to all sprayable materials.
In plasma spray devices, an arc is formed in between two electrodes in a plasma forming gas, which usually consists of either argon/hydrogen or argon/helium. As the plasma gas is heated by the arc, it expands and is accelerated through a shaped nozzle, creating velocities up to MACH 2. Temperatures in the arc zone approach 36,000Â°F (20,000Â°K). Temperatures in the plasma jet are still 18,000Â°F (10,000Â°K) several centimeters form the exit of the nozzle.
Flame spray is divided into three subcategories, based on the form of the feedstock material, either powder-, wire-, or rod-flame spray. Flame spray coating utilizes combustible gasses to create the energy necessary to melt the coating material. Combustion is essentially unconfined, in that there is no extension nozzle in which acceleration can occur. Common fuel gases include hydrogen, acetylene, propane, natural gas, etc. The lower temperatures and velocities associated with conventional flame spraying typically result in higher oxides, porosity, and inclusions in coatings.
Electric-arc spray coating uses a simple, low power arc drawn between two electrically charged wires. Arc spray equipment resembles GMAW (MIG) welding equipment, in the power source and wire feeding units. Common arc spray units are capable of spraying iron and copper alloys at rates up to 40 lbs./hr (18 Kg/hr.) using only 12 kW (42 MJ) of electricity. Electric-arc spray coating produces the fastest coating rates of any thermal spray technology. Electric-arc spray coating devices are thermally efficient and, because there is no flame or plasma, little heat is transferred to the part being coated.
High-velocity, oxy-fuel, (HVOF) devices are a subset of flame spray. HVOF utilizes confined combustion and an extended nozzle to heat and accelerate the powdered coating material. Typical HVOF devices operate at hypersonic gas velocities, i.e. greater than MACH 5. The extreme velocities provide kinetic energy which help produce coatings that are very dense and very well adhered in the as-sprayed condition.
Cold spray is the newest of the thermal spray processes and is mainly found in research labs at this stage of the technology's development.
Cold spray is technically not a true thermal spray process because it does not use thermal energy as the primary energy source to melt materials. Instead cold spray utilizes kinetic energy to project particles onto a prepared surface. The extreme velocities of the process cause plastic deformation of the particles on impact, which in turn creates very dense coatings. An analogy to how a cold spray coating is created is that the particles are essentially friction welded to each other during impact.