THERMAL SPRAYED COATING PROCESS
Thermal Sprayed Coating is a process used to generate a surface coating in order to modify and improve the characteristics of a material without altering its structure. This process protects the material in highly corrosive and wearing working environments.
The main processes are HVOF (High Velocity Oxy Fuel) and APS (Air Plasma Spray) which consist in the deposition through thermal spraying of different families of coatings such as metals, certmet, carbides, ceramics.
In detail, in the case of HVOF the process generates a supersonic jet of particles (Shock Diamond) through internal combustion. These powders, projected onto the material to be coated, solidify rapidly, giving rise to lamellar structures, through the high kinetic energy possessed,
In the APS process, on the other hand, powders are heated and accelerated by a high-temperature plasma jet. The particles impacting the material to be coated generate a homogeneous deposit and provide mechanical and metallurgical adhesion to the substrate without altering its structure. A key feature of the APS process is the ability to spray metallic and nonmetallic materials with a high melting point, as in the case of TBCs (Thermal Barrier Coating), which consist of a ceramic deposit with high porosity.
- Protection from wear, corrosion and oxidation (APS; HVOF)
- Thermal insulation of surfaces (TBC)
- High surface finish and possibility of grinding (APS; HVOF)
- Material carryover for restoration of worn parts (APS)
- Alternative process to chrome plating (HVOF)
- Minimal heat input to the base material
The coating process was patented in 1909 in Switzerland by Dr. Schoop. He employed heat produced by oxyfuel to melt a wire used to repair worn metal parts.
The thermal sprayed coating process is mainly used in the Aerospace and Energy (gas turbines) sectors and is essential for all those products subjected to high mechanical and thermal stresses such as: jet engine components, combustion chambers, cooling tubes, burners and injectors.
In recent years, this technology has also been introduced into the automotive production sector where before it was used almost and only in the “racing” field.