Effect of Mg Addition on Morphology, Roughness and Adhesion of Cr Chromized Layer Produced by Pack Cementation

In the present study, the effect of adding Magnesium (Mg) as a doping element on the morphology and surface characteristics of the chromized layer was investigated. To achieve this, chromized layers were coated and doped by a chromizing process in pack-cementation at ۱۰۵۰°C. The thickness of the doped layer was about ۲۶ µm, whilst chromized was approximately ۲۴ µm. The surface morphology and composition of the coatings were analyzed using scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX). The results showed that a crystalline structure can be successfully deposited by adding Mg as a doping element to the pack mixture. Therefore, Mg acts as a barrier against Cr۲O۳ formation, resulting in a more rich-chromium-zone and forming protective oxide. Moreover, less carbide is formed in the doped layer. The roughness of the layer is enhanced by adding Magnesium (Mg) and it has a lower average roughness (Ra) ۳ times than that of chromized, of about ۰.۳۱۵ µm and ۱.۰۳۹ µm, respectively. In addition, progressive loading scratch was performed at ۱N and ۲۰N. The results demonstrated that Mg in the chromized layer increases the ability to with-stand varying levels of mechanical stress with strength adhesion of about ۱۹.۲۱N and can be more protective than Cr chromized.

Keywords:

Magnesium Doping , Chromium Chromizing , Surface roughness , strength adhesion