Role of Alloying Additions in Microstructure and Wear Behaviour of Galvannealed Coating

Galvannealing is a modified techniques of galvanizing in which annealing is carried out after Zn coating in order to transform the coating surface to wear resistance Zn oxides. The name is referred since galvanizing + annealing steps are carried out subsequently this kind of coatings provide better corrosion resistance as well as wear/scratch resistance there by the damages during transportation could be avoided, the annealing stage lead to the formation of intermetallic layers/precipitates which assist in enhancing the strength and hardness of the coating. Recently it is investigated that Al, Fe, Cr and other alloying elements could be added into the Zn bath during galvanizing so that they can form intermetallic layers or particles on subsequent annealing stages. Further, the annealing temperature and time need to be optimized so that a needle like/flower like morphology can be developed. The size and shape of needles/flowers control the hardness and wear resistance of the coating. Thus it is required to optimize the process parameters so as to control the morphology there by better mechanical properties can be achieved in the present investigation a galvanneled coating is developed using hot dip galvanizing and subsequent annealing. Few set of coatings are developed on mild steel substrate with addition of Al into Zinc bath the concentration of Al varied from 0, 0.1 and 0.2 weight percent respectively.