Papers by Keyword: Thermochemical Treatment

Abstract: The present study has been undertaken to study the microstructure and microhardness of the multi-component B–C–N diffusion coatings developed on AISI M2 high-speed steel substrate at 560 and 650 oC for 1 and 4 h for each temperature respectively. The investigation of the coatings was fulfilled using scanning electron microscopy, energy dispersion spectroscopy and X-ray diffraction analysis. Additionally, Vickers microhardness measurements were performed. The results showed that varying conditions of the thermochemical treatment led to a variety of coatings in the sense of their microstructure and phase composition.

Abstract: The possibility of using modern high-tech flotation equipment at RUSAL Bratsk PJSCis considered, which allows to significantly reduce discharges of extremely hazardous waste of fluorine, sodium, and aluminum to the sludge fields, and to initiate recycling of waste from the sludge fields. The results of operation are presented for a coal foam column flotation system at PJSC RUSAL Bratsk. An innovative technique has been developed allowing to recycle lining waste from aluminum electrolysis pots. The recycling of the waste lining coming from aluminum electrolysis pots is a completely closed waste-free cycle, which provides alumina and cryolite — products that can be used in the aluminum electrolysis, as well as allows using all the secondary solid waste in the satellite cement production.

Abstract: The paper compares the technical characteristics of two thermochemical treatment (TCT) lines for self-tapping screws at OJSC MMK-Metiz. Quenching on TCT line 1 is carried out in the furnace by AUTOMATION SERVICE, while quenching on TCT line 2 is carried out in the furnace by KOHNLE. The authors described quenching and tempering schedules in these two furnaces, studied the microstructure of screws at all process stages, determined technical parameters and properties of finished products after thermochemical treatment. The research showed that the best performance had TCT 2 by KOHNLE. The metallographic analysis indicated more stable parameters of the layer thickness after nitrocarburizing, core and surface hardness, which was in full compliance with regulatory documents. By introducing a better structure of a new TCT line by KOHNLE, a TCT process period became shorter, and a range of self-tapping screws might be extended entailing a higher output of finished products.

Abstract: The article considers issues of increasing wear resistance of cast iron products by methods of thermochemical treatment of their surface layer. Methods are proposed to solve the problem of wear from cast iron of grade EN-JS1060 due to development of technological processes of strengthening treatment. Alternative versions of strengthening technologies are represented by nitrocarburizing, liquid nitriding and carbonitration. Results of examination of control samples at increasing loads after 200 N before catastrophic wear are given. Comparative analysis of these results showed that samples after carbonitration and liquid nitriding had the greatest bearing capacity (1000 N). Carbonitration is selected as a most preferred option of the surface hardening treatment. Non-poisonous cyanoacid salts are used to realize it.

Abstract: According to the standard process, normal electrocorundum is heat treated at 700°C in a rotating drum followed by air cooling. Such heat treatment increases the strength characteristics of abrasive grain. When abrasive paper made from grains with reduced brittleness is working, the effect of reducing the cutting ability due to damage and failure of the cutting surfaces is observed. An increase in the performance characteristics of the abrasive paper was studied by improving the self-sharpening of the grain. Improvement of this performance is achieved by thermochemical treatment in a regulated gas atmosphere and cooling according to a special schedule. Normal electrocorundum during heat treatment in an oxidizing atmosphere changes the structural characteristics due to the decomposition of a solid solution of Ti₂O₃ in α-Al₂O₃ by oxidation to TiO₂. The formation of a block grain structure with microcracks increases the probability of chipping during the grinding tool operation and the appearance of new cutting surfaces.

Abstract: The paper also presents the growth kinetics of the hard layers on the surface grade machinery steels type AISI 9840 with a boron dehydrated paste. The thermochemical treatment was performed at three different temperatures: 1173, 1223, and 1273 K, with 2, 4, 6, and 8 h treatment time for each temperature. The presence of the hard layers FeB and Fe₂B formed on the surface AISI 9840 was confirmed by cross sectional observation by scanning electron microscopy (SEM), XRD analysis and the distribution of alloy elements from hard layers was confirmed by energy dispersive spectroscopy (EDS). Using the law of parabolic growth the mobility of boron was included potential influence of boron, treatment time, temperature and time incubation in hard layers. Finally, nanoindentation technique test the modulus and hardness are obtained of the FeB and Fe₂B hard layers.

Abstract: The paper presents a method based on FEM analysis of determining the strain hardening of elements after the thermochemical treatment. A computational algorithm, which takes into account two factors, has been suggested. Firstly, the gradient of material properties resulting from the changes in the carbon content in the surface layer after the carburizing process. Secondly, the phase transformations occurring during the hardening of the material. The proposed flowchart did not include the flow effect, which greatly reduced the computation time by eliminating tedious CFD calculations. Thanks to an original program Converter coupled with a commercial software's SimHard, SimCarb J Math Pro and Ansys the carburizing process followed by quenching in gases was modeled. In parallel to the numerical calculations the results were verified experimentally. The results of FEM analysis for the tube made of stainless EN 16CrMn5 subjected to three processes of thermochemical treatment have also been presented in the paper. The experimental results were compared with the numerical simulations and a satisfactory convergence has been achieved.

Abstract: Diffusion chromizing of tool steel has been investigated, using a powder method modified by the use of low pressure during the process for the avoidance of the oxidation of the batch. Innovative chromizing novel processes have been carried out in a hot-wall vacuum oven. The processes have been performed in a chromium chloride atmosphere at a low pressure range from 1 to 800 hPa, with treatment temperatures of 850 to 950°C. Studies of layer thickness, its phase composition, and Cr, Fe, and C depth profiles in the diffusion zone of chromized layer have been conducted. The effect of the process parameters, such as time and temperature, on the growth kinetics of diffusion layers has also been investigated. A comparison was made between the layer thickness produced on the tool steel surface using the novel chromizing method, under low pressure, and a traditional chromizing process, by the pack powder method. Chromizing conducted at low pressure was found to be more effective for maximizing the growth rate of diffusion layers than that for chromizing by the traditional pack cementation method.

Abstract: This paper presents investigations of nitrided cases after the glow-discharge nitriding process. The nitrided cases were obtained by using a different chemical composition of gas mixture at the temperature of 450^OC. The glow-discharge nitriding process was carried out on austenitic stainless steel, grade of steel X5CrNi18-10. The chemical composition and phase identification of the nitrided cases were examined by using the glow-discharge optical emission spectrometry (GD-OES) and X-ray diffractometry (XRD)

Abstract: This paper presents investigation of surface layers. The diffusion layers were produced by using different parameters of reactive atmosphere (N2:H2). The research of the surface layers was performed using scanning electron microscope (SEM). The results of energy dispersive X-ray (EDX) analysis and X-ray diffraction (XRD) analysis are presented. Research reveals the influence of chemical constitution of reactive atmosphere on the change of properties of nitrided layers.