Sure, hard facing pertains to thermal spray, though this really is more about depositing’filler’materials onto a metal surface for repair or dimensional restoration. And, normally, these improvements relate with promoting wear resistance, alone.
But did you realize these’overlays’of material could also donate to corrosion prevention, low friction, anti-fretting or galling, even release (nonstick) properties? That which was formerly developed for rebuilding worn parts or individuals with machining errors has become extending into many fields of surface engineering.
The principle of applying thermal spray is very basic. That’s, molten or semi-molten metals, alloys, or ceramics, atomized, are fed toward the job piece by way of a jet stream of air.
As these particles impinge the work surface, they dissipate their heat, quickly cooling, building up, fusing right into a cast-like structure called highly cohesive. Resultant surface finishes, as-sprayed, typically range between 100 and 400 micro inches. So, based on requirements, finish grinding or polishing might be required. (Values under 10 micro inch are quite definitely attainable.)
What types of materials could be applied by thermal spray? The clear answer is most metals, ceramic, cermet(ceramic-metal combinations), tungsten carbide, even organic-based compounds like polyesters.
Adhesion, largely mechanical (versus metallurgical), is excellent. Grit blast, as a way of surface preparation, is typical to best promote adhesion. Though tensile strength could be sometimes superior with higher temperature processes, based on selection of material, through micro-welding or diffusion.
Common types of applications include HVOF (high-velocity oxygen flame), which is comparable to the combustion powder thermal spray process (LVOF), though with increased density, stronger bonds and lower residual tensile stress. Plasma spray and vacuum arc spray are also popular.
Applications continue to develop with this particular technology. Food processing, packaging, molding, plastics, paper and chemical processing, spray on bedliner are just some of the newer, relevant applications. (Many materials are regarded non-objectionable with FDA.)
Ideally, look for thermal spraying processes with minimal heat transfer to your work piece. Just to be sure your surfaces are free from warping, surface distortion. Latest versions include’higher kinetic energy systems’to make certain highest density, particle-to-particle cohesive bonding. The end result is long-lasting, cost-effective, surface performance.
The Teflon and Powder Coating Processes
The goal of both Teflon coating and powder coating is basically similar, although the processes used to apply all of them are slightly different. Both coatings are supposed to impart some specific property to the item that’s being coated. For powder coating, the goal is a protective layer that will keep the item from being damaged, although with Teflon, usually a non-stick surface may be the property that’s meant to be given to the item it will be applied to.
The Powder Coating Process
The powder coating that gets applied is just that-a powder. It basically gets sprayed onto the top and then dries to form a coating. Here’s how a powder coating process works:
1. The powder is placed in the feeder unit for the spray gun. Compressed air inside the system then diffuses it such that it becomes like a liquid though it remains technically a powder.
2. The gun siphons out the powder by pushing high velocity air and propelling the powder from the feeder to the gun.
3. Most guns can spray powder anywhere from 10 to 25 feet. Once the powder leaves the gun, it appears like a cloud that’s moving toward the item that’s being coded.
4. An electrode on the tip of the spray gun emits a demand that’s passed on to the particles of powder if they pass through the tip. That charge causes the powder particles to begin trying to find something to latch onto and form a protective coating over it.
Therefore the powder coating process is quite simple. After it’s been applied, it’s baked onto the item. The whole process is simple to a typical painting job, except powder coating includes a great many benefits over ordinary paint. As an example, any powder that doesn’t affix to the item could be recycled, and the coating it provides is much thicker than paint. So powder coating is ways to offer a smooth, protective coating to something, so what about Teflon coating?