Linde North America (www.linde.com), a member of The Linde Group, a gases and engineering company, introduced its new Linspray CO₂ cooling technology, which significantly reduces cooling time in the thermal spray process while maintaining the correct temperature and minimizing the risk of overheating. This is especially important when working on parts with thin walls or with heat-sensitive substrate materials, such as titanium, magnesium, and aluminum. During thermal spray operations excess head deposition and high temperatures can cause residual stresses, cracking and impaired adhesion between coating and substrate. The Linspray CO₂-based cooling system that minimizes the overheating risk and enhances the quality of the thermal-spray process, according to Linde.

Conventional cooling blows compressed air through nozzles directed at the part to reduce temperatures and minimize overheating risk - a method that's very inefficient, said Joe Berkmanns, manufacturing segment manager, Linde North America.

“While some believe this method is inexpensive because air is free, the indirect costs can often be quite high. When using air, cooling does not occur quickly enough in many cases, and cooling breaks must be programmed into the process. This places the spray gun in a parked position, wastes fuel and spray metal powder, and results in a throughput reduction,” Berkmanns said. “CO₂ is the most effective dry cooling agent because it forms snow with a high latent heat of sublimation at -78° C. Also, the CO₂ storage and delivery can be tailored to the customer's exact requirements. For example, for customers who use thermal spraying only occasionally, such as job shops doing re-work maintenance, liquid CO₂ can be stored easily in a few high-pressure cylinders. Users with more frequent cooling needs - such as full-blown parts manufacturing operations - can store CO₂ in larger cryogenic vessels,” Berkmanns explained. In either case, special, Linde-designed nozzles convert the CO₂ to snow and enable uniform, directed and continuous cooling results without any clogging, which can result in surface inconsistencies. The nozzle is designed to produce the highest amount of CO₂ snow, while optimizing cooling by minimizing the amount of CO₂ gas produced.