Influence of ion nitriding and vacuum carburizing on wear resistance of VKS-7 and VKS-10 steels
Engineering Education # 06, June 2013
Significant resources for improving the set of performance characteristics of essential machine parts are gathered in development of new technologies of thermal and thermochemical treatment, based on activation of processes of diffusion saturation and providing volumetric and surface ultra-finely-divided or nanostructured condition of constructional materials. Results of estimating wear resistance and micro-hardness of VKS-7 and VKS-10 steels after complex treatment, including two stages: 1 - preliminary plastic deformation by a warm compression method and 2 - ion nitriding or vacuum carburizing were presented. A conclusion on the correlation between hardness and wear resistance was drawn.
Investigation of durability of VKS-7 and VKS-10 steels after vacuum carbonization and vacuum carbonitriding
Engineering Education # 05, May 2013
Development of new technologies of thermal and thermochemical treatment, based on the activation of cementation processes and which could provide volume and surface finely-divided or nanostructured state of constructional materials appeared to be a very powerful method to increase the durability of critical machine elements. Results of estimating the durability and micro-hardness of VKS -7 and VKS-10 steels were presented in this article after complex processing which consisted of two stages: 1 – preliminary plastic deformation by means of warm shortening and 2- plasma nitration or vacuum carbonization. Analysis of the relation between hardness and durability was carried out.
Simulation of ion nitriding
Engineering Education # 01, January 2013
The authors analyzed processes occurring in the saturating medium and work material; the analysis allowed to account for reasons of high rate of phase growth during ion nitriding. It was shown that the kinetic coefficient is a link between technological parameters and process output results. An algorithm for calculating process output characteristics is proposed.
Nanoclusters in solid solutions of iron-chromium and their influence on hardness of the nitrided layer of steel 38H2MYUA
Engineering Education # 11, November 2012
The authors established the influence of preliminary heat treatment (annealing at 950°C, 0.5 hrs, cooled with furnace + tempering at the interval of 500-700°C) on hardness of the nitrided layer of steel 38H2MYUA (nitriding at 500°C, 30 h). Similar results were obtained in a model of carbon-free alloy Fe-4% Cr. By the method of nuclear gamma resonance spectroscopy (the Mossbauer effect) on the model alloy it was established that Fe-Cr clusters are formed during the cooling process starting from 950°C and the subsequent tempering. Clustering affects the size and number of particles of chromium nitride formed during subsequent nitriding at 500°C. Depending on the heat treatment before nitriding, Fe-Cr clusters are characterized by different filling of chromium atoms of the first and second coordination spheres of iron. According to the Mössbauer spectra after annealing at 950°C and tempering at 550°C, during the following 10 hrs before nitriding in the structure of the solid solution clusters are formed, and they correspond to the crystalline structure of the σ-phase Fe-Cr system: Frank-Kasper polyhedra with 14 vertices.
Calculation of thermal pre-treatment before nitriding on the size of the nuclei of iron nitride.
Engineering Education # 11, November 2012
The authors calculated the effect of temperature and time parameters of thermal pre-treatment of structural steels at the initial stages of formation of a fine structure before nitriding. With the program "Termodin" developed at the department "Materials science" in Bauman MSTU the authors calculated the critical radius of the nuclei of iron nitride, diffusion parameters, kinetic parameters of nucleation and growth phase Fe4N, time of formation of a given volume fraction of γ/ phase during isothermal holding in the high holiday for binary alloys Fe-5, 6% N by mass. Kinetic curves of decomposition of the supersaturated solid solution with formation of a given volume fraction of γ/ phase were built. The authors also calculated prediction modes of thermal pre-treatment on the size of hardening phases.
Degree of plastic resistance as the selection criterion of the nitriding mode for tribotechnical purposes
Engineering Education # 07, July 2012
The authors present results of experimental evaluation of ability of surface layers of nitride steels and alloys to resist damage under conditions of deformation during friction. A new approach to comparative evaluation and selection of nitriding mode of parts and friction joints is proposed.