Papers by Keyword: Chromium Carbide

Abstract: Chromium carbide coatings deposited on mechanical parts by different techniques have an interesting hardness, wear-resistant and corrosion resistance. Some studies show that chromium carbides produced by physical vapor deposition methods and revealed a superior hardness present a poor adherence to their substrates. The objective of this study is to indirectly obtain a hard, and adherent coating of chromium carbide by using a conversion treatment including carburizing treatment of steel substrate, deposition of a pure chromium layer, and annealing treatment of coated carburized steel under a carbonic gas atmosphere. Treatment temperature has an effect on the partial or complete conversion of chromium film as a result of the diffusion and precipitation process. The transformation rate of chromium into both chromium carbide layers was investigated. For 1 h of holding treatment, chromium film was totally transformed at 900 °C into chromium carbide film which presented high hardness and excellent adhesion.

Abstract: In this paper, we present the development of new types of boron carbide-based ceramics. Boron carbide is applied in the electronics and nuclear industries as well as for production of the grinding and abrasive materials, protective plates for body armor. The interaction of boron carbide with chromium nano-oxide additives (1-5 wt.%) during sintering was studied by mass spectrometry. It is shown that the formation of chromium nano-boride takes place at the stages of formation of metallic chromium, the lowest chromium boride and chromium carbide. The maximum solubility of chromium in the boron carbide lattice was found to be 0.5 wt.%. A composite material based on boron carbide, В₄С with CrB₂ nano-inclusions, was prepared. The bending strength and modulus of normal elasticity were equal to 44.6 MPa and 449.5 GPa, respectively. Micro-hardness and residual porosity were determined to be 40 GPa and 5-7 %.

Abstract: The Article presents the findings of the studies of the microstructure, chemical and phase composition of the Cr₃C₂-Ti system alloys obtained by the explosion. Scanning electron microscopy, energy dispersive and x-ray diffraction analyses were used. The program Thermo-Calc software was used to calculate the equilibrium phases. The phase composition of the compact was shown to fully correspond to that of the initial powder mixture during explosive pressing in the modes of heating from 300 ̊С to 600 ̊С. When heated above 600 ̊С, the chemical interaction of the initial components begins with the formation of new boundary phases. Meanwhile, there is a change in the sample destruction nature and a significant increase in hardness, which points to the hard alloy consolidation. The increase in the powder mixture heating in shock waves to 1000 ̊С leads to intensive macrochemical interaction of the powder mixture components and to formation of an equilibrium phase composition. The established temperature limits determine the most appropriate parameters of shock-wave loading when producing hard alloys by explosive pressing.

Abstract: Twin-wire indirect arc welding (TWIAW) is a novel welding technology with high deposition efficiency and low dilution rate, which is especially suitable for wear-resistant surfacing. In this study, wear-resistant surfacing layer was prepareted on low-carbon steel using flux cored wire by TWIAW. The influence of welding parameters on droplet transition and the surfacing layers property were studied. In the TWIAW process, due to rapidly solidification of the weld pool, wear-resistant reinforced phase synthesized through metallurgical reaction mainly finished in the droplet transfer stage using the welding arc. The welding parameters not only affected the droplet transfer frequency and size, but also affected the microstructure of the surfacing layer. The main reinforcing phase in the surfacing layer was chromium carbide. "Lean carbon" phenomenon could be observed along the grain boundary in the matrix when the welding current was small. The increasing of the welding current could prompt the metallurgical reaction. The wear resistance of the surfacing layers depends on the distribution of the chromium carbide and the matrix microstructure.

Abstract: From the hard and anti-corrosions coatings, we found the chromium carbides, these components were discovered by large studies; like thin films since years ago. They were pointed a good quality for the protection of steel, because of their thermal and mechanical properties for this reason, it was used in many fields for protection. Plus: their hardness and their important function in mechanical coatings. The aim of this work joins a study of the effect of the thermal treatment on mechanical and structural properties of the Cr/steel system. Thin films were deposited by cathodic magnetron sputtering on the steel substrates of 100C6, contain 1% wt of carbon. Samples were annealing in vacuum temperature interval between 700 to 1000 °C since 45 min, it forms the chromium carbides. Then pieces are characterising by X-ray diffraction, X-ray microanalysis and scanning electron microscopy. Mechanical properties are analysing by Vickers test. The X-ray diffraction analyse point the formation of the Cr₇C₃, Cr₂₃C₆ carbides at 900°C; they transformed to ternary carbides in a highest temperature, but the Cr₃C₂ doesn’t appear. The X-ray microanalysis shows the diffusion mechanism between the chromium film and the steel sample; from the variation of: Cr, Fe, C, O elements concentration with the change of annealing temperature. The variation of annealing temperature shows a clean improvement in mechanical and structural properties, like the adhesion and the micro-hardness.

Abstract: The article reports findings on theoretically-calculated data and experimental results obtained with scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy methods of the analysis of hard alloys produced by the explosive compaction of the Cr₃C₂ chromium carbide powders with titanium, first in the original condition and then after heating to 1200 °C. It was established that when heated to 600 °С the phase composition of hard alloys does not change and corresponds to the composition of the original components of the powder mixture. When the heating temperature was increased to 650 °С, new fine powder fractions emerged at the “chromium carbide – titanium” interface. At the temperature of 700 °С two separate diffusion layers emerged and grew in the opposite directions. Due to this growth the source phases in the alloy fully disappeared at 1200 °С and two equilibrium phases were formed.

Abstract: The tribological characteristics of the Cr₃С₂–Ti system hard alloys produced by the explosive compaction of powders containing 20, 30, 40, and 50 vol. % of the titanium binder are investigated. The general approach to selecting the optimal structure and properties of wear-resistant hard alloys for manufacturing the slider bearing parts working in conjunction with silicified graphite under water lubrication conditions is formulated. It is shown that, to attain the highest antifriction characteristics and minimal wear of the friction unit, the alloy should have the maximally possible hardness with the minimally admissible specific volume of a carbide phase in the material structure. It is established that such alloys have higher antifriction characteristics and wear resistance than silicified graphite and the Cr₃C₂–20% Ni-type materials produced by conventional methods.

Abstract: The production of a new type of hard alloys by explosive compaction of chromium carbide (Cr₃C₂) and titanium powder mixtures was investigated. The phase composition of the fabricated alloys was studied using scanning electron probe microanalysis. The chemical composition of the alloy components does not change, and no redistribution of the elements was observed. The formation characteristics of the interfaces between the material components during shock wave processing were investigated using electron microscopy. The explosion compaction of high melting carbide and metal powder mixtures results in the formation of consolidated hard alloys during the compaction stage.

Abstract: Metal matrix composite layers were fabricated on AISI 304L substrate by diode laser surface alloying with direct injection of chromium carbide Cr₃C₂ powder into the molten-pool. The influence of laser alloying parameters on the quality of the alloyed layers were investigated. The alloyed layers were examined by optical metallography and scanning electron microscopy. Comparative erosion tests between the AISI 304L substrate and the alloyed layers have been performed following the ASTM G 76 standard test method. The uniform laser beam intensity profile of the laser used ensures to produce fully dense alloying layers with homogenous distribution of Cr₃C₂ particle throughout the matrix alloy. Distribution and dissolution of Cr₃C₂ particles are strongly dependent on the laser power level. The alloyed layers exhited noticeable increased erosion resistance in comparison to AISI 304L substrate for both 30° and 90° impact angles.

Abstract: The influence of chromium cast iron Cr8 treatment by Fe-45Si-6Mg-0,5REM modifier on the structure, phase transformation and heat resistance was studied experimentally.It is demonstrated that during modifying of chromium cast iron Cr8 the alloying effect takes place. The initial cast iron structure which consists of alloyed ferrite, carbide (Cr,Fe)₇C₃ and cementite (Fe,Cr)₃C is transformed as in the process of chromium alloying according to modifier consumption increase. At the modifier consumption of 0,15 % the mass quota of cementite (Fe,Cr)₃C decreases from 3,2 % to zero, and the mass quota of carbide (Cr,Fe)₇C₃ increases from 20 % up to 30 %.