Papers by Keyword: Wear

Abstract: This paper presents an attempt to learn mechanical, corrosive and abrasive wear mechanisms and wear mechanisms in refrigerating compressor systems. The range of author’s examinations includes electrolytic liquids with abrasive material used in the food industry, especially in the sugar industry and lubricating oils polluted with refrigerant occurring in stationary and mobile refrigerating compressor systems. Tests on the wear mechanisms in complex service conditions show that the total wear occurring in tribological pairs due to simultaneous occurrence of destructive processes: frictional, corrosive and abrasive, is not a simple superposition of their individual effects occurring in conditions of their independent interactions. On the basis of carried out experiments with the use of mathematical methods for experimental designs, a statistical model describing the complex process of simultaneous wear was formulated. This model enables forecasting the wear and indicates that the abrasive wear is of dominating character. In the compressor refrigerating systems, the oil–refrigerant system is characterized by complex relations. Refrigerants andcompressor oils create compounds causing the accelerated wear of refrigerating compressors. The complex dependencies in case of the oil–refrigerant compound, cause that the lubricating and anti-wear properties are much worse than in case of pure oil. In case of exceeding their mutual miscibility, part of the agent is absorbed by oil. More stringent regulations concerning the protection of the ozone layer lead to the appearance of new agents creating new compounds with oils. In order to examine the influence of the compounds on the wear processes in the refrigerating compressors, we made a test stand. The stand is built of real elements of the refrigerating system consisting of, among others, a dismountable half-hermetic compressor. The stand, built for testing the model wear processes occurring in the refrigerating compressors, will be used for tribological tests in the atmosphere of refrigerants under regular loads conditions.The purpose of the performed examination is to develop methods of wear phenomena modelling in the complex service conditions in the sectors of food production and refrigerated storage .

Abstract: Surface mechanical pulse treatment of medium-carbon low alloyed steels by high speed friction has been developed. Its major features are surfaces provided with the nanostructure with grain size of 20...50 nm, increased surface hardness and, correspondingly wear resistance. This nanostructure is subjected to the tempering temperature of 500 °С. Hydrogen charging of the strengthening materials decreases their plasticity, more considerably in steels with higher carbon content. However, it is possible to use mechanical pulse treatment to achieve high characteristics of strength, wear resistance and plasticity in hydrogen, selecting as-received matrix structure and the tempering temperature after surface treatment.

Abstract: Excellent tribological properties of hard materials surface are desirable in several sectors of industry. Diamond-like carbon (DLC) coatings are well known for their low friction, excellent wear resistance, and high hardness. In this work, DLC films were deposited on AISI M2 steel using a modified PECVD pulsed-DC discharge. Multilayer of carbon and silicon were grown, alternately. Samples were produced with different layer thickness for carbon and silicon, and the same parameters for each material layer, in order to investigate friction coefficient in each layer, evaluate rate deposition variation and the gradient behavior of different layers. Raman spectroscopy was used to verify the structural arrangement of carbon atoms. The films were also characterized by scanning electron microscopy and EDX. Tribological tests were performed to observe adhesion between layers and substrate, friction, and wear. The results showed the variation of friction coefficient and that deposition rate declines when increasing number of layers.

Abstract: This paper presents the results of a systematic dry hobbing experiment performed on a general mechanical transmission type of hobbing machine. All four types of coated HSS hobs demonstrate satisfactory cutting performance applicable enough to practical production. Some related details such as the characteristics of hob wear, the effect of chip crush behavior and cutting speed are also discussed based on the experiment results.

Abstract: Wire electrical discharge machining (WEDM) is a specialized thermal machining process, capable of accurately machining parts with different hardness, complex shapes and sharp edges that are very difficult to be machined by the traditional machining processes. The practical technology of the WEDM process is based on the conventional EDM sparking phenomenon utilizing the widely accepted noncontact technique of material removal.In this paper, the effects of various process parameters of WEDM like pulse on time (T_on), peak current (IP), wire feed (WF) and wire tension (WT) have been investigated to study their impact on wear of wire of ELECTRONICA SPRINTCUT WEDM machine.It is found that the wear is influenced with increase in pulse on time (T_on) and wire tension.

Abstract: Article deals with analysis of production and characteristics of ceramic coatings applied using HVOF technology. It presents the results of research focused on quality evaluation of HVOF coatings on the basis of WC-Co and impact of Boron Nitride protective layer. HVOF coatings were exposed to hard tribocorrosive conditions. For determining of corrosive resistance of coatings 1M solution of NaCl, potentiodynamic tests and accelerated salt spray test were used. Experiment confirmed that using of Boron Nitride protective coating clearly improves corrosive resistance of the coating on the basis of WC-Co even in hard combined tribocorrosive conditions. Protective layer seals the pores in the structure of coating and thus prevents the formation of corrosion and subsequent depreciation of coating in various corrosive environments. Using of protective layer thus improves lifetime and reliability of spraying and the part itself. Improved lifetime positively influences also the economics of the operation of energetic equipment in which these coating are used.

Abstract: In this research, micro-hardness and wear resistance of two types of electroless coatings were investigated including Ni-P and Ni-P-B₄C composite coatings. Dispersible B₄C particles and electroless Ni-P alloy were codeposited on carbon steel by electroless plating and then heat treated at 200, 400 and 600 °C for 1 h, respectively. The cross-section morphology and microstructure of the composite coatings were characterized. Meanwhile, the micro-hardness and tribological behavior of composite coatings were evaluated. The results showed that the Ni-P-B₄C composite coating presents better wear resistance in comparison with that of Ni-P coating. The Ni-P-B₄C composite coating with heat treated at 400 °C exhibits high micro-hardness and good wear resistance, which the highest hardness is 1200 HV, the minimum wear weight loss is 0.12 mg and the lowest friction coefficient is 0.2054.

Abstract: The problems of the dynamic interaction of the terminal pair of elements are covered. Physical properties of the material, behavior of their characteristics and the features of mechanical interaction are taken into account. Mathematical model of dynamics of contact layer conductivity fractal destruction for sliding shank of sections contact pairs is created.

Abstract: Cr/WC-Ni composite coating was prepared on Cr12MoV die steel by thermal spray technique, and then further treated using laser cladding technique. WC powders was coated Cr by D.C. magnetron sputtering method. The structure, composition, hardness, morphology were analyzed and measured by XRD and SEM and hardness tester. Tribological experiments were carried out on an abrasion machine. The results showed thatCr film prevented WC decomposition, and Cr/WC-Ni coating had the higher hardness values compared with WC-Ni coating. After the treatment with the laser cladding, the coating surface was uniform and compact and had no cracks, the boding between the matrix and coating surface had a good metallurgical bonding, and sub-surface showed a higher hardness.

Abstract: The steel fiber reinforced ceramic matrix friction material is prepared by nitrogen protection sintering method. The specimens of the three different friction materials containing different content of alumina, clay and potash feldspar are formulated. The friction and wear characteristics are determined by using the XD-MSM constant speed friction tester. The testing results show that the increase of potash feldspar and the decrease of clay content make friction coefficient become more stable and diminish the sensitivity of friction coefficient to the temperature changes. This study also identify that among the three friction materials investigated, the main wear mechanism converts from grain pull-out and fracture wear to adhesion wear and abrasive wear.