Technique for accelerated tests of samples for wear resistance

A review of the existing methods of accelerated abrasive wear tests is presented. The shortcomings of the technique implemented on an IM-01 installation of the VISKHOM design, as well as the Brinell-Howarth technique for laboratory studies, in which a powder abrasive is used are discussed, e.g., a problem of a uniform distribution of a free-flowing abrasive material over the surface of the contact zone, as well as problems of ensuring the stability of the supply of the abrasive material during the experiment. The goal of the study is to develop a methodology for comparative assessment of the wear resistance, excluding noted shortcomings. The tests were carried out on an M-1 installation using plate specimens 60 × 40 × 3 mm. The abrasive material used was a radial flap wheel 150 – 220 mm in diameter (width 30 mm, bore diameter 30 – 40 mm). The degree of wear was determined by a decrease in the mass of the sample by weighing on a balance with an accuracy of 0.1 mg before and after testing. The test results were considered as a relative wear resistance ε equal to the ratio of the wear resistance of the test specimen to the wear resistance of the reference one. The use of relative wear resistance makes it possible to increase the accuracy of the results obtained due to elimination of the influence of natural changes in external parameters that determine the intensity of wear during the test. The developed installation provides significant shortening of the accelerated comparative test (8 min) compared to 40 min on an IM-1, the structure and grain size of the working fluid, the constancy of the load in the contact zone and the speed of interaction between the sample and the tool being the same. Flap wheels of various grain sizes provide application of the device to a wide range of tasks without preliminary grinding of the samples and necessitate only their preliminary cleaning from slags and large particles after applying wear-resistant coatings.

Prediction of cavitation wear resistance of metallic materials based on the results of measuring the roughness of a worn surface

A method is proposed for predicting the relative cavitation wear resistance of metallic materials using the ratio of the durations of their incubation periods of wear, based on measuring the rate of increase in surface roughness during the incubation period. The experiments were carried out in fresh water and artificial seawater. Keywords: cavitation wear, metal alloy, relative wear resistance, incubation period, surface roughness. [email protected]

NEW DEVICE AND PROCEDURE FOR COMPARATIVE TESTS OF THE ABRASIVE WEAR RESISTANCE OF 65G STEEL COATINGS OBTAINED BY HIGH-SPEED HDPE BORATING

Abrasive wear tests are a complex, time-consuming and long-term type of research on the wear-resistant properties of materials. Known methods for the experimental determination of the wear resistance of materials based on abrasive wear require an assessment of the wear resistance corresponding to the characteristics of field tests of parts with reinforcing coatings applied using high- frequency currents. (Research purpose) The research purpose is in analyzing the existing methods of testing for abrasive wear in the development of technological processes to increase the wear resistance of the surfaces of machine parts in comparison with the methodology developed by VIM, as well as comparing the methods of laboratory tests and field tests with the method proposed in this paper. (Materials and methods) Authors chose the IM-01 installation of the VISKHOM design for laboratory research, which uses powder abrasive. The article describes the most similar methods of foreign authors. The drill bits of Amazone seeders were strengthened according to the selected testing technology. The plates with a size of 60x40 and a thickness of 5-7 millimeters were selected as samples for testing the relative wear resistance. According to the VIM method, an abrasive radial petal circle is used as an abrasive material on the M-1 installation. (Results and discussion) The test results are expressed by the relative wear resistance index ε, which is equal to the ratio of the wear resistance of the test sample to the wear resistance of the standard. The use of the relative wear resistance index allows to increase the accuracy of the results obtained due to the exclusion of the influence of natural changes in external parameters that determine the wear rate during the test. (Conclusions) The proposed device makes it possible to provide accelerated comparative tests of samples and improve the stability of obtaining wear characteristics in a relatively short time (with the practical use of the device, the time spent on testing of one sample was about 8 minutes).

Improving the Efficiency of Grinding Sugar Beet in Centrifugal Beet Cutters

Introduction. Grinding sugar beet should be carried out with minimal losses in centrifugal beet cutters with specially designed knives that provide frequent and constant chaotic longitudinal-lateral cutting of circular conductive beet knots. The objective of the work is to increase the reliability of the knives of centrifugal beet cutters by structural and technological strengthening in the process of their production and restoration. Materials and Methods. The state of the cutting edges of the knives was determined by using the micrometric measurement of the wear and deformation of the edges. Physical and mechanical indicators were analyzed based on the values of wear resistance, microhardness, and bending endurance. Results. The analyzes of the defective state of the knives of centrifugal beet cutters and theoretical studies of the grinding process have allowed formulating the factors affecting the permeability of the beet chips and the efficiency of their grinding with knives of a special diamond-shaped design. Experimental studies have made it possible to establish dynamically substantiated design parameters of an improved knurled knife. Discussion and Conclusion. The proposed measures ensured an increase in the durability of knives by 27–30%, the relative wear resistance of cutting edges by 20%, the limit of endurance of cutting edges for bending by 25% and a shift increase in the length of chips by 18–20% with an increase in its permeability by 16–18%.

STUDY OF THE RESISTANCE OF TAPERS WHEN APPLYING METAL-CLADDING LUBRICANT-COOLING FLUIDS

The paper discusses the results of comparative tests of the period of tap resistance in various technological environments. The workpieces were processed in the medium of industrial oil I-30 with using a 10 and 20 percent solution of the metal-coating additive “Valena SV” in the same oil. The tests were performed on M10×1 taps made of high-speed steel of the R6M5 brand during the production of through threaded holes in samples made of steel of the Steel 40X brand. The cutting speed varied from 5.7 to 11.1 m/min at the rotary speed of the tool ranging between 180 and 355 rpm. Based on the experimental material, a regression model of the relationship between the relative wear resistance and the additive concentration, and cutting speed has been determined. The author has evaluated the model adequacy and the convergence of the experimental and calculated data. It has been found that at a cutting speed of 11.1 m/min and an additive concentration of 20%, the relative wear resistance of the taps increased by 3.1 times. The results obtained testify to the eff ectiveness of the composition and confi rm the hypothesis of an increase in the wear resistance of the taps in the medium of metal-plating lubricating-and-cooling liquids.

Investigation of structure and properties of surfaced coatings based on titanium nickelide

The conditions for formation of coatings based on titanium nickelide under the argon double-arc surfacing of titanium and nickel electrode wires on the titanium samples were shown. Results of evaluating the quality of formation and geometric parameters of the weld at the double-arc surfacing were presented. Relationship between the ratio of feed rates of nickel and titanium wires and chemical composition of the deposited coatings has been established. Investigations of the structure of the surfaced metal at the surfacing modes was carried out. It has been shown that argon double-arc surfacing formed coatings based on the Ti2Ni and TiNi. Mechanical and operational properties of surfaced coatings were studied — hardness, resistance to abrasion and heat resistance at 800 °С. Relative wear resistance of surfaced coatings is higher than that of titanium samples. Dependence of the relative wear resistance of the coatings on the chemical and phase composition was shown. Dependence of heat resistance of the surfaced coatings on the modes of surfacing and the chemical composition of the weld metal is established.

Assessment of Durability and Service Life of Two-Layer Hardened Earth Cutters in Various Soil Conditions

Introduction. The earth cutter resource depends on the characteristics of the materials they are made from. In particular, the important parameters that directly affect the tillage tool parts efficiency and durability are the values and ratios of the coefficients of relative wear resistance of the two-layer parts materials, as a rule of the hardened deposited layer and the base material (steel). It is established that the characteristics of the relative wear resistance of the materials for earth cutter parts vary depending on the treated soil properties. The objectives of the study are to consider the influence of soil conditions on the values of the relative wear resistance coefficients of two-layer earth cutter part materials and to carry out a comparative assessment of their resource and use efficiency. Materials and Methods. The authors gave a generalized dependence of the wear proportionality to the existing specific pressures values. The characteristics of soil abrasion were given. The scientific substantiation of the changes in the characteristics of the materials wear resistance at various values of specific pressures was given. Results. The results of the operational resource tests and the studies of two-layer and monometallic earth cutters are presented. The influences of the values of the operating specific pressures on the coefficients of the relative wear resistance of the materials for the tillage machine parts are determined. Discussion and Conclusion. The authors have found out that the coefficients of relative wear resistance of materials are not constant, but vary depending on the current surface specific pressures. The correlation of the specific pressure values with the parameters of the tillage operation, in particular with the furrow slice hardness was established. It has been found that while increasing the cultivated soil hardness, the coefficients of various materials relative wear resistance get closer to each other. The difference varies from 1.80 to1.85 times.

TRIBOLOGICAL PROPERTIES OF POLYURETHANES IN ABRASIVE SOIL MASS

This paper presents a comparative study of polyurethane wear in abrasive soil mass. Two types of polyurethanes of various chemical compositions and untreated 38GSA steel were tested, the latter being used as a reference standard. The study was conducted in a natural soil mass at a “rotating bowl” stand. Relative wear resistance was determined from measurements of mass wear for the materials under study. The conditions of the surface of the materials under wear tests were analysed.

ENGINEERING AND RESEARCH OF WEARABILITY COATING ON THE BASIS OF HIGH-STRENGTH STEEL

Methods of the optical metallography, TEM, SEM- technique, X-ray analysis, tests for hardness and wear resistance, are resulted results of research and optimization of structure and properties facing materials with austenite-martensite structure and with various quantity of strengthening phases. The maintenance in facing material austenite 38% is shown, that, martensite 32% and strengthening phases of 30% provide the highest relative wear resistance  = 5.89 and hardness HRC 61.