Hot Dip Aluminum Coating Process in Steel and Cast Iron
AbstractHot-dip aluminizing (HDA) process is an effective coating technique to protect the surface of steel and cast irons from corrosion, oxidation, decarburization and wear at high temperatures. Because of these advantages, HDA is used to protect the surface of steels used in the hot stamping process in automotive industry against oxidation and decarburization. Also, HDA can provide additional oxidation resistance to high silicon ductile irons used in high-temperature applications such as furnace parts and exhaust manifolds. HDA is generally performed by dipping the substrates into molten Al or Al–Si alloys. This process results in the formation of various Fe–Al intermetallics along the coating. For example, immersing the substrate into pure Al produces Fe2Al5 phase close to the substrate, and FeAl3 phase close to the surface. A high-temperature diffusion annealing after HDA provides interdiffusion within the coating and thus can change the type and order of the intermetallics. In this study, the effect of HDA on structural, morphological and mechanical properties of the coating formed on a low carbon steel, a stainless steel and a high silicon ductile iron were addressed. In addition, effect of successive application of HDA and austempering on wear and corrosion properties of the ductile iron was also discussed.