The Properties of Cr-Al-N Based Coatings Formed on AISI D2 Steel by Thermo-Reactive Diffusion Technique

In this study, chromium aluminum nitride coating was applied on pre-nitrided AISI D2 steel by the thermo-reactive deposition technique in a powder mixture consisting of ferrochromium, aluminum, ammonium chloride, and alumina at 1000 degrees C for 2 h. Steels were gas nitrided for the purpose to enrich the surfaces with nitrogen of the steels in a nitrogen and ammonia atmosphere at 560 degrees C for 8 h. The effect of aluminum content in the powder mixture on the Cr-Al-N layer properties was investigated. The coated samples were characterized by X-ray diffraction analysis, scanning electron microscope, and micro-hardness tests. Chromium aluminum nitride layer formed on the pre-nitrided AISI D2 steel was compact and homogeneous. Electron dispersive spectrometer results showed that coating layer includes chromium, aluminum, and nitrogen. X-ray studies showed that the phases formed in the coating layers on the steel surfaces are Cr2N, (Cr,Fe)(2)N1-x, AIN, and Fe2N. The depth of the Cr-Al-N layer ranged from 10.01 +/- 1.2 to 13.2 +/- 1.7 mu m, depending on the aluminum content. The hardness of the coated layers produced on AISI D2 steel are changing from 1743 +/- 150 HV0.01 to 2067 +/- 160 HV0.01 depending on bath compositions. DOI: 10.12693/APhysPolA.123.271