Determination Of Carbonization Depths In Ti Substrates In Diamond Growth Atmospheres And Modified Diffusion Models

Behaviors of diamond coated Ti-related parts are significantly affected by carbonized interlayers, so it is essential to determine or predict the carbonization depth during diamond growth. Following the Fick's law of diffusion with carbon concentration-dependent diffusion coefficients, it is roughly predicted that carbonization depths in Ti and Ti-6Al-4V substrates hardly reach 30 mu m within a long duration of 16 h. After trying some characterization methods (XPS, EDS, metallographic analysis and ToF-SIMS), the EDS line scanning is selected as the practical one with sufficient accuracy and convenience. Influences of some critical factors, including growth duration, substrate temperature, reactant pressure and acetone (carbon source) concentration, are studied and discussed. Considering all of the factors, especially those related to the diamond coverage that can suppress carbon diffusion, the modified diffusion models for describing the carbon diffusion, are constructed, defining carbon concentration and diamond coverage (duration, pressure, carbon concentration)-dependent diffusion coefficients. Such the models can be used for well predicting the carbonization depths under most conditions, which are valuable for controlling the carbonized layers during fabrications of diamond coated Ti-related components facing to various applications. (C) 2020 Elsevier B.V. All rights reserved.