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 1050°C. The thickness of the doped layer was about 26 µm, whilst chromized was approximately 24 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 Cr2O3 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) 3 times than that of chromized, of about 0.315 µm and 1.039 µm, respectively. In addition, progressive loading scratch was performed at 1N and 20N. 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 19.21N and can be more protective than Cr chromized.