Frequently Asked Questions

Account Suspended!

*If you&#;re the owner of this website and have questions, reach out to Bluehost. We&#;re happy to help.

Link to Litong

Balancing the flow with the right thermal spray process parameters

So, how do we achieve all this required temperature control? Essentially, it&#;s all about removing thermal energy in a controlled way at the same time we are applying it i.e. balancing the heat flow. Mostly this involves the use of auxiliary cooling in the form of directed compressed air, sometimes liquid carbon dioxide (CO2) and occasionally liquid nitrogen.

Most applications will be adequately cooled via the use of clean, dry, compressed air (remember, we don&#;t want to contaminate our prepared surface or our coating as it&#;s being deposited). Cooling jets can either be fixed (see Figure 9) or gun mounted (see Figure 10). In both cases, it is important to control supply pressures, cooling jet sizes and distance to the substrate, as all these factors will affect the heat withdrawal process. Care should also be taken not to allow the cooling stream to impinge on the spray plume as this can have a (in most cases) negative effect on the coating.

The use of fixed siphon cooling jets can be especially beneficial as they can be positioned close to the area being sprayed and can deliver large volumes of air &#;siphoned&#; in from the immediate environment.

Gun-mounted cooling jets have the advantage of traveling with the gun so that they can therefore efficiently cool a moving area immediately adjacent to the spray stream. Of course, they can&#;t deliver as much cooling media as a fixed cooling nozzle.

In particular cases where significant amounts of fine material is generated by the spraying process, gun mounted jets can be positioned so that the cooling media intersects just past the spray distance (see Figure 10). This positioning ensures that the plume is not negatively affected by the cooling, but the surface being coated is cleaned of fine product on either side of the flame as it sweeps over the surface. This can change a &#;rough as sandpaper&#; coating to one that is as smooth as a baby&#;s derriere.

Contact us to discuss your requirements of thermal spray roller. Our experienced sales team can help you identify the options that best suit your needs.

The more energetic the spray process, the more challenges there are to control the temperature regime the coated part experiences. For processes such as HVOF-LF and -GF, there can be often a need to use cryogenic cooling methods. More heat going in, more cooling required to remove it.

Figure 11 shows a Diamond Jet&#; HVOF GF system spraying a shaft using gun mounted
CO2 jets. In this case the CO2 is supplied in liquid form. As it exits the nozzles, it changes to a &#;solid&#; snow. When this hits the surface, the energy required to transform from solid, to liquid, to gas provides a very efficient method of heat removal.

To properly control the balancing effect between heat absorbed and heat removed, it is good practice to use some sort of temperature measurement device. These can be contact or non-contact systems depending on the type of job being sprayed. In all cases, it makes sense to define and monitor the part temperature profile during the spraying process to ensure no damage is encountered by either the part and/or the coating.

Cooling processes should be regarded as a key process variable as they can have a significant effect on the properties of the coating and the success of the application. As such, care should be taken to record such variables as air pressure, cooling nozzle to work distance, nozzle size, etc., to ensure repeatability.

To conclude the thermal spraying process parameters

Hopefully, this article has provided some background on some of the thermal spraying process parameters that are important to consider when aiming for a coating which meets your and the customer&#;s expectations. There are many parameters which affect the thermal spray process. Manipulation and temperature control are just two more aspects which need to be carefully controlled. My main message is therefore that they should be treated as a process parameter with values and tolerances properly applied. Without this, coating quality can be affected in a ways that are unexpected and quite possibly costly.

Are you interested in learning more about steel coil color coating line suppliers? Contact us today to secure an expert consultation!