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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.

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.

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 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.

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.

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.

It is essential to investigate the tribological maturation of tissue engineered cartilage that is to be used in medical applications. The friction properties of tissue engineered cartilage have been measured using flat counter surfaces such as stainless steel, glass or ceramics. However, the measured friction properties were significantly inferior to those of natural cartilage, likely because of cartilage adhesion to the counter surface. In this study, a poly(2-methacryloyloxyethyl phosphorylcholine (MPC)) grafted surface is proposed as an appropriate counter surface for cartilage friction evaluation due to the material’s ability to reduce the adhesion and reproduce natural tribological conditions. The poly(MPC) grafted surfaces were prepared by atom transfer radical polymerization (ATRP). The friction coefficients for natural cartilage that were measured on the poly(MPC) grafted surface were lower than 0.01 at the sliding velocities of 0.08 and 0.008 mm/s, which is equivalent to that for natural cartilage-on-cartilage. The friction coefficients for the tissue engineered cartilage were reduced with cultivation time at low sliding velocities. Thus it is suggested that the proposed system is able to measure the tribological maturation of tissue engineered cartilage in a more natural lubricating environment.

The effect of dispersed oxide phases of Y 2 O 3 -TiO 2 type on the wear rate and the friction coefficient of the high-chromium martensitic 18Kh12V2 and ferritic 01Kh13V2 steels upon sliding friction in pair with the 40Kh12 steel has been studied. The structure of these materials has been analyzed by metallographic and electron-microscopic methods. It has been shown that the presence of about 0.5% dispersed oxide particles, including nanosized ones, in the structure of the ferritic 01Kh13V2 steel exerts a complex influence on the wear resistance of this steel. Upon dry friction under the conditions of adhesive wear, the 01Kh12V2 steel alloyed with oxides is characterized by a low wear resistance. It is caused by an increased brittleness of the steel, which activates the processes of seizure and deep tearing at the friction surface of the steel. In the case of lubricated friction (boundary friction regime), dispersed oxide phases exert a great positive influence on the wear resistance of the steel. The wear rate of the oxide-strengthened ferritic steel in this case is about twice as low as that of the steel nonalloyed with oxides. It is caused by the formation of numerous pores in the surface layer of the alloyed steel in place of spalled oxides. The formation of pores helps better retention of a lubricant in the friction zone (the effect of self-lubrication), which decreases the probability of adhesive inter-action between the contacting steel surfaces. It has been found out that the alloying of a high-chromium martensitic 18Kh12V2 steel with a small amount (∼0.3%) of oxides of the Y 2 O 3 + TiO 2 type does not exert a noticeable influence on the tribological properties of the steel under consideration. The oxide phase does not affect noticeably the magnitude of the friction coefficient of the steels tested.

In nanofluid minimum quantity lubrication (NMQL) grinding of titanium (Ti) alloy, existing nanoparticles cannot solve the technical bottleneck of high surface integrity. Therefore, graphene (GR) nanoparticles, which have excellent lubrication performance, were applied in NMQL. The tribological properties of GR nanofluid on wheel–workpiece interface were studied by friction and wear test. In the experiment, 0.5–3 nm thick GR nanoparticles were used to prepare 3% vol. palm oil-based nanofluid. Ball-disc experiment under grinding conditions was carried out on the friction and wear tester. Grinding balls with SiC abrasive grains (to simulate the grinding wheel) and Ti-6Al-4V disc (to simulate the workpiece) were used. Load force was set for simulation of pressure boundary condition of the grinding wheel–workpiece interface. Stratiform nanoparticles (MoS 2 , MoO 3 , and HBN) were used as the comparison group. Results demonstrated that GR nanofluid achieved smaller friction coefficient (0.295), error bars (0.0029), and area of scratches (182,940 μm 2 ). GR nanoparticles with small gravity and large specific surface area improved the viscosity of nanofluid and consequently the lubrication performance. The plane hexagonal honeycomb structure determines the strong lubrication stability and abrasive resistance of the GR nanoparticles. The scanning electron microscope (SEM) and energy dispersive spectrometer (EDS) images of the scratch surface also verified the above conclusions.

Lubricant additives can effectively enhance the performance and environmental adaptability of lubricants and reduce the energy loss and machine wear caused by friction. Nanomaterials, as important additive materials, have an essential role in the research and development of new lubricants, whose lubrication performances and mechanisms are not only related to their physical and chemical properties, but also influenced by the geometric shape. In this paper, the friction reduction and antiwear performances of nanomaterials as lubricant additives are first reviewed according to the classification of the dimensions, and their lubrication mechanisms and influence rules are revealed. Second, the recent research progress of composite nanomaterials as lubrication additives is introduced, focusing on their synergistic mechanism to improve the lubrication performance further. Finally, we briefly discuss the challenges faced by nanoadditives and provide an outlook on future research. The review expects to provide new ideas for the selection and development of lubricant additives to expand the application of nanoadditives.