Chromium carbide coating of steels by a thermoreactive diffusion process

Abstract

This study is concerned with the thermo-chemical treatments of metals and alloys and more particularly with the composition of chromium-carbide diffusion coatings to be deposited on steel components. Three groups of steels (C60, 50CrMo4, X210Cr12) were used for the present work. The process involves heating polished steel samples to 1080 degrees C preferably for 2 to 8 h in contact with a powder of chromium, inert filler (Al2O3), and ammonium chloride. The chromium carbide coatings were examined by means of optical microscopy, microhardness measurement and x ray diffraction technique. The hardness of carbide coating layers was found to be within 1100 - 1500 HV. The measured thicknesses of the chromium carbide layers were found 10.2 - 41.6 mu m. The thickness of the carbide layer depends on coating time, temperature and composition of the base material. The hardness depends on the coating temperature and on the composition of the substrate but it is independent on the coating time. This coating method can be applied to the carbide coating of structural and tool steels.