•The evolution of self-organization under extreme frictional conditions has been studied.•Comprehensive characterization of the tribo-films was made using various surface analytical ...techniques.•During the running-in stage, mullite tribo-ceramics predominate on the surface of the nano-multilayer coating, establishing a functional hierarchy within the layer of tribo-films.•It is possible to control tribo-film evolution during self-organization by means of an increase in structural complexity and the non-equilibrium state of the surface engineered layer.
The evolution of the self-organization process where dissipative structures are formed under the extreme frictional conditions associated with high performance dry machining of hardened steels has been studied in detail. The emphasis was on the progressive studies of surface transformations within multilayer and monolayer TiAlCrSiYN-based PVD coatings during the running-in stage of wear when self-organization process occurs. The coating layer was characterized by high resolution electron energy-loss spectroscopy (HREELS). It is shown that the nano-multilayer coating possesses higher non-equilibrium structure in comparison to the monolayer. Comprehensive studies of the tribo-films (dissipative structures) formed on the friction surface were made using a number of advanced surface characterization techniques such as X-ray photoelectron spectroscopy (XPS) and X-ray absorption near edge structure (XANES). The data obtained for the tribo-films was combined with the detailed TEM studies of the structural and phase transformations within the underlying coating layer. This data was related to the micro-mechanical characteristics of the coating layer and its wear resistance. It was demonstrated that the evolution of the self-organization process is strongly controlled by the characteristics of the tribo-films formed at different stages of the wear process. Within running-in stage (after length of cut of 15m) fully protective mullite tribo-films predominantly form on the surface of nano-multilayer coating, establishing a functional hierarchy within the layer of tribo-films. This reduces entropy production during friction and leads to significant surface damage reduction and wear rate stabilization. In contrast, in a monolayer coating with a lower structural complexity, a variety of protective and non-protective tribo-films form during the running-in stage, which cannot fully protect the surface. Therefore the wear rate on the monolayer is not stabilized and its wear resistance is lower. The results obtained show that it is possible to control tribo-films evolution during self-organization by means of increase in structural complexity and the non-equilibrium state of the surface engineered layer with simultaneous tuning of its integrative behaviour.
The study discusses the subject of lubrication in the processes of hot die forging with the consideration of the durability of forging tools and instrumentation. It presents a literature research as ...well as the authors’ own investigations of the effect of the use of cooling and lubrication agents, the amount of the dosage as well as the direction of its application, and also the factors influencing the tribological conditions. The lubrication devices and systems currently applied in the industry have been analyzed as well. On this basis, making use of their knowledge and experience, the authors have developed and constructed a lubricating device. The elaborated system, implemented into the industrial process, makes it possible to select and ensure the optimal tribological conditions of the process by way of controlling the amount and frequency of the applied lubricant dosage. It can constitute an alternative for the manual method of lubricant application, which is dependent on the human factor, or the fully automated, yet expensive, lubrication systems. The obtained test results point to potential possibilities of a permanent introduction of the constructed device also into other forging processes, through its integration with a manipulator. The proposed solution ensures more stability and higher repeatability of the lubrication conditions as well as increases the efficiency of the production process, thus significantly reducing the unit costs of the production of forgings
This study investigates accelerated physical–chemical processes in a complex adaptive surface-engineered system represented by a nano-multilayer TiAlCrSiYN/TiAlCrN PVD coating under the extreme ...tribological conditions of ultra-high-performance dry machining of hardened H 13 tool steel. These processes are similar to the different catalyzing phenomena. Experimental results of tool life vs. wear rate, SEM/TEM data of the worn surfaces, XPS and EDS data of tribo-films formed on the friction surfaces, and chip surface morphology are presented in this study. The corresponding relationships between self-organization, self-organized criticality, and various catalyzing phenomena were evaluated on the basis of the accrued data. A method of enhancing these processes through the variation of machining conditions is also outlined, which resulted in the improvement of coated tool life by 35%.
The paper concerns selected aspects of the application of cooling–lubricating agents as well as methods and devices assigned to lubrication in hot die forging processes realized at elevated and high ...temperatures in the context of their effect on the quality of the forgings and the durability of the forging instrumentation. An analysis was made of the currently used lubricants and their properties and applications in selected industrial forging processes, and a review was conducted of the presently applied cooling–lubricating systems and devices. The article also presents the authors’ own studies referring to the effect of the application of lubricating and cooling agents, the volume of the lubricant portion, the times and directions of its application, and other factors affecting tribological conditions. It also presents lubricating devices constructed based on the knowledge and experience of the authors. The elaborated systems, introduced into selected forging processes, make it possible to examine the effect of the volume and time-frequency of the applied lubricant dose on the wear of the tools and also to select and ensure the optimal tribological conditions in the process with respect to durability. The obtained research results, which were confirmed in the industrial process, indicate the great potential of implementing such devices also in other forging processes because the proposed solutions ensure greater repeatability and stability of working conditions. This increases the efficiency of production and thus significantly reduces the unit production costs, as a two-fold increase (from 8000 to 16,000 forgings) in tool life has been observed.
The paper is focused on investigating the quality of two grades of thermally sprayed coatings deposited by high-velocity oxygen fuel (HVOF) technology. One grade contains WC hard particles in an ...environmentally progressive Ni- and Co-free FeCrAl matrix, while the second coating contains WC and WB hard particles in a cobalt matrix. The aim of the experimental work was to determine the effect of thermal cyclic loading on the coatings' resistance to adhesive, abrasive and erosive wear. Abrasive wear was evaluated using abrasive cloth of two grit sizes, and erosive wear was evaluated by a dry-pot wear test in a pin mill at two sample angles. Adhesion wear resistance of the coatings was determined by a sliding wear test under dry friction conditions and in a 1 mol water solution of NaCl. Corrosion resistance of the coatings was evaluated using potentiodynamic polarization tests. Metallographic cross-sections were used for measurement of the microhardness and thickness and for line energy-dispersive X-ray (EDX) analysis. The tests proved the excellent resistance of both coatings against adhesive, abrasive, and erosive wear, as well as the ability of the WC-WB-Co coating to withstand alternating temperatures of up to 600 °C. The "green carbide" coating (WC-FeCrAl) can be recommended as an environmentally friendly replacement for Ni- and Co-containing coatings, but its operating temperature is strictly limited to 500 °C in air.
This paper concerns an analysis of the tribological conditions and the effect of the use of seven lubricating agents dedicated to a process of precision forging on a hammer in multiple systems. In ...particular, it performs a review of the most popular methods of determining the friction coefficient in the aspect of the obtained results. On this basis, the selected method of friction coefficient determination was a hot ring upsetting test for two forging materials: carbon steel (16MnCrS5) and stainless steel (316Ti). The test samples were prepared in the shape of a ring with precisely defined dimensions, and, next, they were subjected to an upsetting process on a hydraulic hammer under conditions similar to those present in an industrial forging process, and the characteristic geometrical features and friction coefficients were determined. Additionally, measurements of the geometrical changes were made with the use of 3D scanning for the extreme friction coefficient values in order to perform their comparison. The obtained results showed that for carbon steel the lowest achieved value was in the case of Lubrodal F185 (µ = 0.24) A and the highest for Lubr_hot_press 123HD (µ = 0.32); in turn, for stainless steel the lowest value µ = 0.19 was achieved for Graphitex CR 7 and the highest for Graphitex CR720K (µ = 0.29). Moreover, for these conditions, numerical modeling was conducted in the Forge 3.0 NxT program, in order to analyze the obtained results and verify the correctness and agreement of the friction coefficients determined in the ring test, on the basis of the geometrical changes. The data obtained in the computer simulation confirmed the possibility of obtaining a good agreement between the FEM (Finite Elements Method) and experimental trials, as the modeling provides reliable information on the plastic deformations and can be used as an alternative method of examining the friction conditions in industrial forging processes.
It is essential to know the correct thickness to which a product can be developed with adequate strength and ductility. In this study the Influence of sheet thickness on formability of material ...Commercially Pure Titanium under Polytetra Floro Ethylene (PTFE) lubrication condition is experimentally investigated according to BIS-IS 10175 standard using Erichsen Cupping Test. Generally formability of a material depends on intrinsic material properties and prevailing process parameters. The process parameters such as lubricating conditions which alter tribological conditions during forming are taken into considerations. The process parameters are analyzed by selecting different thickness specimens of commercial pure titanium alloy. It is evaluated that the formability of the material commercially pure titanium alloy varies on thickness variation. It is also evaluated that formability of materials selected in the study differs under different lubricating conditions.
The spike forging test is still commonly used although there are some new tribology test methods, but each designer would like to give their own parameters. Considering the spike height difference ...between low friction and high friction as the evaluation index, an optimal spike forging test developed using finite element simulations based on orthogonal optimization method and sensitivity analysis of tribological conditions of selected key design parameters was carried out. The spike height does not always monotonically decrease with the increase in friction factor in the scheme with improper parameters; therefore, the design of spike forging test should be critically evaluated before assessing tribological conditions. According to the optimized parameters, a simplified set-up of spike forging test was designed, and two retainers with a clearance fit and the billet with a chamfer were prepared to position the test billet. Finally, four different tribological conditions, including dry polytetrafluoroethylene lubricant, multipurpose grease, VG32 oil, and dry condition, in aluminum forging were chosen as a case study for the optimized design of spike forging test, and correspondingly, the lubricating effect was distinguished.
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