EVALUATION OF SURFACE FINISH AND ITS EFFECT ON PACKED DIFFUSION ALUMINISATION OF LOW ALLOY STEEL COMPONENT

ABSTRACT Medium alloy carbon steel has become the choice of material for high temperature applications due to its desirable mechanical properties at elevated temperature and corrosive environment. The medium alloy carbon steel undergoes various types of corrosion like carburization, oxidation based on various industrial applications. Various methods are employed to obtain protective coating on the surface of the metal. The best suited technique among the available techniques is diffusion aluminisation using pack cementation process .The salient feature of diffusion aluminisation process is that a diffusion as well as deposition layer can be enriched on the metal surface. The Aluminizing coating technology is an established technique wherein several studies and researches are being carried out to study the kinetics of aluminisation on the metal surface. However there is lack of information and research gap regarding the role of the surface attributes and the profiles and its effect on the anti-corrosion coating thickness of the metal.This paper aims to study the role of surface roughness (Ra)on the coating thickness of the EN24 steel samples achieved by three different machining processes such as turning, grinding, abrasive flow finishing machining. The paper also investigates the influence of the surface roughness (Ra)on hardening and annealing prior to the packed diffusion aluminisation process followed by tempering of both the sets post aluminisation process. The diffusion pack cementation process was carried out at temperature of about 500????C to 900????C. The analysis was carried out to study the coating characteristics using optical light microscope, EDX using Scanning Electron Microscope (SEM), X-ray Powder Diffraction (XRD) and micro hardness. KEYWORDS – Diffusion aluminisation process, Surface roughness, Turning, Grinding, Abrasive flow finishing machining