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Authors
Affiliations
1 Department of Mechanical Engineering, B.S.A. Crescent Engineering College, Chennai-600048, IN
2 IP Rings Ltd, D 11/12, Industrial Estate, Maraimalainagar-603209, IN
3 Department of Production Technology, Anna University, MIT Campus, Chennai-600044, IN
Source
Manufacturing Technology Today, Vol 6, No 6 (2007), Pagination: 20-26
Abstract
Duplex coating is used in surface engineering to provide improved wear and corrosion resistance. The present study aims at hot dip aluminizing of a steel base followed by diffusion and nitriding treatments. The base material chosen for study is BS970 grade EN 8 steel (or 080M40). The specimens were dipped in molten aluminium-silicon alloy bath (11-13% Si) for various dip times (5-23 minutes) at 988K and diffused at 1173K for 8 hours. The diffused specimens were gas nitrided for 10 hours 50 minutes. The effect of dip time on coating thickness, diffusion layer thickness, microhardness and microstructure of aluminized, diffused and nitrided steel specimens were studied. The aluminium coating thickness does not significantly increase with the dip time beyond certain duration. The experimental studies indicate that the diffused layer thickness varies from 54-69 μm. The prolonged dipping time does not provide any significant advantage in increasing the diffused layer thickness. The surface hardness of EN 8 steel could he increased to about 800 HV when aluminized diffused and to about 1200 HV on subsequent nitriding. The increase in the hardness is attributed to the formation of hard nitride layer (Al-N). This methodology could be adopted for automotive and other engineering applications.
