Thermal Spray Coating Process

1. Clean Part & Qualify for Repair

The substrate surface of rods, shafts or other industrial parts are first prepared by cleaning and de-greasing.

The parts are magnaflux tested. This determines if the part is repairable or not. Internal and outside dimensions are documented, along with content of material and hardness of material.

For power cylinder bores, this process changes slightly, 

• Typically, parts are placed in a vat of caustic soda for 24 to 48 hours.
• Cylinder bores are pressure-tested and magnaflux tested. Learn about our proprietary ThermAlloy® Process for cylinder bores.

2. Surface Preparation

The substrate surface is then cleaned, de-greased, and roughened it to create a suitable surface profile for adhesion. If the surface is not properly cleaned, the coating will not be able to properly bind to the surface, causing the part to not work as intended.

This may involve techniques such as abrasive blasting, chemical cleaning, or mechanical roughening.

3. Coating Application

The selected coating material is fed into a thermal spray device, which can be one of several types, including flame spray, arc spray, plasma spray, or high-velocity oxy-fuel (HVOF) spray. Each method has its own unique characteristics and operating principles.

Flame Spray: In flame spray, the coating material is melted and propelled onto the substrate surface using a combustion flame generated by a fuel gas and oxygen mixture. The coating material can be either a powder or a melted wire.

Arc Spray: In arc spray, an electric arc is generated between two consumable wire electrodes, melting the wire tips. Compressed air is then used to atomize and propel the molten droplets onto the substrate.

Plasma Spray: Plasma spray involves using a plasma torch to ionize a carrier gas and then inject the coating material into the plasma flame. The high temperatures melt and accelerate the particles onto the substrate.

HVOF Spray: High-velocity oxy-fuel (HVOF) spray utilizes a combustion process where fuel gas and oxygen are mixed and ignited in a combustion chamber. The resulting high-velocity gas stream propels the molten coating material onto the substrate.

ThermAlloy® (Exline's proprietary thermal spray coating) in the bore of the cylinder, Babbitt coating in the piston, and Safety Seal (piston ring) is the perfect recipe for extending the life of your cylinders and pistons.

Consider ThermAlloy® instead of hard chrome for rebuilding compressor's essential components.

4. Finish Grind

Because the certain sprayed coatings have an inherently rough surface, it is frequently necessary to post process the surface. Also, certain materials may require additional processing in the form of post-coating diffusion, nitrating, hot isostatic pressing, or shot peening.

The coating adds thickness to the piece, so many components will need to be machined down to achieve their final dimension. Sealing the final coating may also be necessary to fill pores and microcrask, which could cause major problems if left alone.

5. Packaged and Shipped

Parts are packaged for shipment.