Flame plating procedures such as Linde’s Detonation Gun provide a bond which is both mechanical and metallurgical in nature. The Detonation Gun procedure is a process patented by Union Carbide (Linde Division). Coatings are produced by passing measured quantities of powder, oxygen and acetylene into a firing chamber. A timed spark then detonates the mixture, creating a hot (6000°F) high-speed gas stream which in turn instantly heats the powder particles. Powders are composed principally of tungsten carbine particles. Nearly molten particles leave the firing chamber at approximately 2500 fps, impinging on the surface of the piston rod and produce a microscopic welding-type bond. Because of the intense noise generated, the operation is carried out in a soundproof room, remotely controlled by an operator. Rapid-fire detonations, as the firing chamber moves along the rod, build up the coating to the specified thickness. Linde provides several D-Gun powder compositions to suit a variety of process conditions.
• Low base material temperature [less than 300°F (149°C)] are maintained during application. No metallurgical changes to the base material occur.
• No distortions or warping.
• No subsequent stress relief or heat treatment required.
• Bond strength is very good (10-25 ksi). Bond is both mechanical and metallurgical in nature. (For some coatings, bond strength can be further improved by post-application heat treatment.)
• Can be applied to a wide variety of base materials.
• Low porosity (sealers can be used to further reduce porosity).
• Good oil retention characteristics.
• Good corrosion protection.
• Very hard coating (Rc 67-76).
• Proprietary process closely controlled by Union Carbide. Good quality control.
• Relatively high cost.
• Limited coating thickness (generally <0.010 inch). • Finish grinding required.