Chromium Carbide Films Research Articles

A Thermodynamic Approach to the CVD of Chromium and of Chromium Carbides Starting from Cr(C6H6)2

Partial equilibrium thermodynamic calculations were used to simulate the MOCVD of chromium and of chromium carbide films starting from Cr(C6H6)2. They showed that by simultaneously increasing the operating pressure and decreasing the precursor molar fraction, the carbon content of the films can be decreased. A modification of the composition of the reactive gas on the growing surface to a C6H6/Cr value of 0.2 was proposed in order to fit available experimental data. This surface composition at equilibrium is in excellent agreement with estimates made by using a model based on the control of deposition and consequently of carbon incorporation by surface adsorption of benzene.

クロムーモリブデン鋼にC,Cr複合拡散処理により形成させた被膜の界面構造と密着性

In order to form thick and hard chromium carbide film on 2 1/4 Cr-1Mo alloy steel, (C, Cr) combined diffusion treatment which was composed of carburizing treatment and chromizing treatment was proposed. Thick chromium carbide film (>30 μm) could be obtained by selecting carburizing and chromizing conditions. The formed surface was composed of chromium carbide film on the substrate and precipitated chromium carbide particles below the film. Furthermore, the obtained film consisted of fine (about 0.5 μm) Cr23C6 and Cr7C3 particles. The precipitated chromium carbide particles below the film mainly consisted of Cr23C6. The distribution of these Cr23C6 particles gradually decreased in proportion to the distance from the boundary between the film and the substrate. The film showed excellent adhesion to the substrate under thermal cyclic condition from 400°C up to 700°C. It was thought that the chromium carbide film which partly penetrated into the grain boundary of the substrate acted as an anchoring effect and the precipitated chromium carbide particles below the film acted as a thermal expansion relief layer. The obtained film showed high hardness over Hv 1000.

Assessment of tetra-alkylchromium compounds for low temperature organo-metallic chemical vapour deposition of Cr-based coatings

Chromium carbide films have been deposited by organo-metallic chemical vapour deposition using the tetra-alkylchromium compounds Cr[C(CH 3) 3] 4 and Cr[CH 2C(CH 3) 3] 4 under reduced pressure in the temperature ranges 100–150 °C and 250–350 °C respectively. The blocking of β-decomposition mechanisms increases the thermal stability of the second precursor, and subsequently increases the deposition temperature range and palliates the reagent depletion in the gas phase. Both the higher thermodynamic stability of Cr[CH 2Si(CH 3) 3] 4 and the lower kinetic lability of the ligand CH 2SiMe 3 result in a significantly higher temperature range of deposition (450–515 °C). However, the decomposition of this third precursor is not as clean as expected, even under hydrogen atmosphere, since Si and C are incorporated in the films leading to an original amorphous material containing a mixture of metallic and covalent bonds. Comparison of the results from the different precursors leads to the hypothesis that a cyclometallation mechanism could be a dominant initial step for the removal of CH 2C(CH 3) 3 and CH 2Si(CH 3) 3 ligands.

Structural characterization of chromium carbide coatings deposited at low temperature by low pressure chemical vapour decomposition using dicumene chromium

Abstract The growth of chromium carbide coatings by pyrolysis of dicumene chromium in a hot-wall low pressure chemical vapour deposition reactor has been investigated between 300 and 550 °C. Amorphous chromium carbide films were obtained in the low temperature range 300 - 500 °C whereas a textured crystalline Cr 7 C 3 phase was grown above 500 °C. The total carbon content was independent of the deposition temperature and amounted to a carbon excess of about 30% compared with the Cr 7 C 3 stoichiometry. Electron spectroscopy for chemical analysis of both amorphous and crystalline coatings confirms the presence of this carbon excess since about 30% - 40% of free carbon was found. A heterogeneous structural model composed of the Cr 7 C 3 phase and free carbon is proposed both for crystalline and amorphous coatings.

Reactive-magnetron-sputtered chromium carbide films

Chromium carbide films were deposited by r.f. reactive magnetron sputtering of chromium in an acetylene plasma. The carbon-to-chromium ratio in the films was found to increase with substrate temperature and acetylene partial pressure, resulting in a supersaturated solid solution of carbon in a chromium matrix and the Cr 23C 6 phase. The microstructure and composition of the films were found to be very sensitive to the deposition temperature and incorporated hydrogen and hydrocarbon radicals.

Chemical Vapor Deposition of Chromium Carbide from Organometallic Precursors

ABSTRACTChemical vapor deposition from CpCr(CO)3H, Cr(CH2CMe3)4, and Cr(NPri2)3at low pressures yields chromium carbide films at temperatures as low as 330 °C. The films are mirror-bright and extremely smooth with no significant features observable by SEM. In general, films prepared at higher temperatures had lower resistivities, and were more likely to be crystalline than those prepared at lower temperatures. However, amorphous films deposited at 330 °C were much harder than the crystalline films. Chemical vapor deposition from Cr(NPri2)3resulted in carbide films with the most desirable properties.

Absorptance and emittance of metal carbide selective surfaces sputter deposited onto glass tubes

An investigation of the absorptance and emittance of selective absorbing surfaces based on reactively sputtered chromium carbide and stainless steel carbide films overlayed on sputtered copper is described. These surfaces have suitable properties for inclusion in all glass tubular evacuated collectors. Graded metal carbide surfaces have absorptance α≈94% compared to α≈82% for homogeneous surfaces, however, the latter have considerably lower emittance at elevated temperature and so may be more suited to high temperature operation. Both homogeneous and graded surfaces deteriorate at temperatures above 300°C in vacuum due to diffusion of carbon within the selective surface. Enhancement of the absorptance of graded surfaces to α≈96% has been achieved by applying a light coating of carbon particles to the surfaces, however, at the expense of ≈1% increase in emittance.

Ion-Plated Thin Films for Anti-Wear Applications

Anti-wear applications of ion-plated thin films have been investigated. Ion-plated films always showed better wear-resistance to fretting than the other vacuum-deposited films. Ion-plated chromium, gold, cadmium, zirconium, and boron carbide films have been effective in the prevention of fretting. Durability-surface was expressed three-dimensionally, and high hardness and large ion-radius were analyzed to be important factors for wear-resistance in air. Adhesion of coatings is critical to wear-resistance. Structures of film, interface, and substrate were studied with transmission and scanning electron microscopes and these all were found to be correlated with a good adhesion of ion-plated films. Microfibrous structure of film, microscopically intricate interface, and lattice defect concentration in substrate caused high adhesive strength of ion-plated films.