No 2 (2015)
- Year: 2015
- Articles: 7
- URL: https://bakhtiniada.ru/1994-6309/issue/view/19979
- Description:
Full Issue
TECHNOLOGY
Efficiency of microporous coatings grinding using coolant
Abstract
Wear-resistant microporous coatings on nickel and iron base falls into the category of hard materials, which abrasive treatment is associated with considerable difficulties. The main causes of intractability of these coatings by grinding lie in the rapid loss of cutting properties of the abrasive wheel, due to wear, bluntness and active adhesion of the coating on the working surface of the tool. The results of investigations of the cutting ability of wheels made of aluminum oxide and silicon carbide in microporous coatings grinding without coolant (without coolant), using tap water and oil are presented in the article. The wear of the abrasive grains and the nature of their interaction with the material being processed depending on the composition of the coolant are studied. Ways to improve the efficiency of the grinding process of microporous coatings by applying a chemically active media that can reduce interaction between coatings and abrasive materials are suggested. New coolants with chemically active substances, passivating the surface of microporous coatings on the round outer grinding operations are tested. A proposal about feasibility of replacing the oil compositions of cutting fluids on aqueous compositions that allow to increase the processing capacity and durability of wheels made of aluminum oxide and silicon carbide, while reducing the height of the microscopic inequalities in comparison with the oil compositions is put. Comprehensive assessment of test results by the rating method showed that the most effective in the round external grinding of microporous coatings on nickel and iron-based is the aqueous solution of emulsol "EPM - 1sh."
Obrabotka Metallov / Metal Working and Material Science. 2015;(2):6-16
6-16
The hardening of friction wedge of freight car bogie
Abstract
The technological process of hardening of the wedge of freight car bogie made of gray cast iron SCH18, using high-induction treatment is developed. Source of energy is presented by a high-frequency generator HFG 5-60 / 0.066 60 kW. Hardening process included heating of the vertical surface of the wedge and the subsequent quenching at full water screen of the heating zone. The thickness of the hardened layer with a hardness of 57 HRC is above 3.5 mm. According to the developed technology a pilot batch of products, which was successfully running endurance tests on the proof ground of rail transport in Scherbinka city, is produced. During the test a distance run was more than 1 million km while the standard run is not less than 500 thousand km. In this case, the allowable amount of wear of the friction wedges is not increased, and the coefficient of relative friction of the friction oscillation damper answered to the specifications.
Obrabotka Metallov / Metal Working and Material Science. 2015;(2):17-23
17-23
Test for adequacy of model of particle spreading over the substrate during plasma spraying of thermal barrier coatings
Abstract
A mathematical description of the process of spreading and simultaneous solidification of the liquid particles, when it collides with the solid surface of the substrate is presented and approximate numerical methods for the calculation are constructed in the article. These algorithms are a continuation of numerical studies on the development of approximate methods of calculation, which examined simplified models for individual variables, such as temperature in the particle, in the substrate, in the contact area, for finding the velocity field for determining the shape of the spreaded particle. The developed model allows carrying out numerical experiments to study the collision process of an individual drop with the spatial surface and its’ spreading, as well as the formation of the structure of plasma coatings. The results show that the numerical methods are quite effective in the study of nonlinear problems. On the basis of experimental studies of processes of interaction of the particles with the substrate and spreading on it the adequacy of the developed theoretical dependencies is shown.
Obrabotka Metallov / Metal Working and Material Science. 2015;(2):24-31
24-31
EQUIPMENT. INSTRUMENTS
Investigation of the strength of carrier constructions of industrial building
Abstract
Purpose: Frameworks are widely used for the roof of industrial buildings. The advantage of frameworks appears when it is needed to cover long spans. In this context, the following problem is formulated: investigation of the concrete industrial buildings carrier constructions’ (shop for metalworking, warehouse) state of stress and state of strain and design of the rational constructions. Carrier constructions correspond to the spatial frameworks. Methods: The finite elements method is used for the calculation of the state of stress and state of strain. Results: The calculation of the characteristic fragment of the building (the angle of intersection of two mutually perpendicular sections) found that the maximum stress in the rod is 139.6 MPa, the maximum vertical displacement is 10.51 mm, and weight is 51112.72 kg. For practical realization of the considered structures is recommended to use the steel square pipe 70×70×5 (mm) GOST 8639-82, rectangular steel pipes 150×100×8 (mm), 100×70×5 (mm) GOST 8645-82, welded steel pipes 273×9 (mm), 219×8 (mm) GOST 10704-91. Discussion: The numerical model of carrier constructions of building adequately reflects their stress-strain state. Thus, final stresses are equal to 139.6 MPa that is less than working stress (142.4 MPa) and, consequently, the structural strength is ensured. The maximum vertical displacement is 10.51 mm that is less than the maximum permissible vertical bend (64 mm), specified by design standards, therefore, rigidity is ensured. Stability calculations of rods under compression showed that the condition of stability is performed for all rods. In particular, for the most loaded element (a column with 219 mm in diameter of, wall thickness of 8 mm, 1900 mm in length) real pressure of 40.9 MPa is less than the rigidity working stress of 205.2 MPa. Thus, the developed design satisfies the strength reliability conditions (norms of strength, stiffness and stability).
Obrabotka Metallov / Metal Working and Material Science. 2015;(2):32-38
32-38
MATERIAL SCIENCE
The technology of producing a composite material based on a multifunctional oxide ceramics
Abstract
The synthesis of composite SHS powders with components of solid lubricant is described. The powders of the following composition: Al 2O 3 + 30% TiO 2 + 12.5% MoS 2; Al 2O 3 + 30% TiO 2 + 12.5% CaF 2 were investigated. The synthesis of compositions was carried out in a reactor using self-propagation mode without supply of energy from an external source in a nitrogen-oxygen atmosphere with an oxygen content of 10…25 wt.% and a pressure of 0.1…0.9 MPa. Such atmosphere is needed for the oxidation reaction of titanium powder. For spheroidization particles of the composite powder were added into the plasma jet and sprayed into a steel cylinder with a length of 1 m filled with argon. The degree of spheroidization was determined using the form factor of the particles by optical metallography. The power of the plasma jet was varied from 30 to 40 kW. The resulting powders are characterized by a complex geometric shape and the development of surface relief of the particles. Application of SHS powders, in contrast to the agglomerates, allows forming high-density coating of eutectic composition promoting improvement physical and mechanical properties. Parameters of friction and wear coatings consisting of carbide ceramic powders and ceramic oxide powders obtained by self-propagating high-temperature synthesis are investigated. The coatings obtained of powder Al 2O 3-30% TiO 2-12.5% MoS 2; produced by self-propagating high-temperature synthesis, are 1.2 times more wear-resistant with the lubricant and 1.3 times - under dry friction for cast iron and steel than the coating obtained from the powder Ni80Cr20-12.5% MoS 2-55% TiC.
Obrabotka Metallov / Metal Working and Material Science. 2015;(2):39-45
39-45
Optimization of the deposition process of wear-resistant coatings based on multifunctional oxide ceramics
Abstract
The optimization of the process parameters for the APS materials Al 2O 3-TiO 2-12% (MoS 2-Ni), Al 2O 3-TiO 2-12% (CaF 2-Ni), obtained by agglomerating finely dispersed blend followed by high temperature sintering and method of self-propagating high-temperature synthesis is made. Spraying of the wear resistant coatings of aluminum oxide - titanium oxide - solid lubricant obtained by the method of agglomerating finely dispersed blend, followed by high temperature sintering and SHS was carried out on a plasma-spraying in air. Such coatings are characterized by high ductility, corrosion resistance and shock resistance, and also have lower values of porosity, uniform steel structure and isotropic properties. Optimization of parameters of the deposition was carried out on the basis of obtainment the maximum utilization factor of the material and the minimum porosity of the coating. The effect of current, spraying distance, the powder particle size distribution, a method for manufacturing the powder utilization factor and the porosity of the coating material, as well as the influence of particle size distribution on adhesion strength of the coating to the substrate and coating hardness is examined. The results of these coatings studies led to the conclusion that the technology for manufacturing powder has a dominant influence on the formation of the coating structure. The use of SHS powders, in contrast to the agglomerates, allows creating high-density coating of eutectic composition, enhancing physical and mechanical properties.
Obrabotka Metallov / Metal Working and Material Science. 2015;(2):46-54
46-54
Influence of rolling and heat treatment on the structure and properties of the coatings fabricated on the titanium substrates by electron beam cladding
Abstract
The influence of rolling and annealing on the structure and properties of VT1-0 titanium with cladded tantalum-containing coatings is estimated. It was found that electron beam treatment contributes to the formation of coatings characterized by the presence of dendritic segregation which is not neutralized by subsequent technological processes. However, the structural investigations revealed that annealing of the rolled material induces transformation of the quenched needlelike structure to the stable one, which is represented by equlaxial grains and lamination. A microhardness level of titanium surface layers after electron beam treatment increased from 165 to 385 HV. Rolling and annealing had no significant effect on the hardness of cladded layers, but they had an impact on hardness of the titanium substrate. Ultimate tensile strength of titanium workpieces after electron beam treatment was approximately equal to tensile strength of commercially pure (cp) titanium (about 420 MPa). Rolling of the composites led to workhardening of the titanium plate and increase of strength up to 610 MPa which was subsequently reduced to about 450 MPa by annealing. Plasticity of investigated materials was lower than plasticity of cp-titanium after all kinds of treatment. Electron beam cladding also induced decreasing the titanium impact strength level to 55 J/cm 2, which decreased to a greater extent (to 40 J/cm 2) after rolling. However, subsequent annealing eliminated the negative effect of technological processes on impact strength of the material and contributed to its increase up to approximately 100 J/cm 2.
Obrabotka Metallov / Metal Working and Material Science. 2015;(2):55-63
55-63