Dry Lubrication Conditions Research Articles

Microstructure and tribological behavior of plasma sprayed NiCrAlY/WC-Co/cenosphere/solid lubricants composite coatings

Present investigation deal with NiCrAlY/WC-Co/Cenosphere/MoS2/CaF2, NiCrAlY/WC-Co/Cenosphere/MoS2/CaSO4 and NiCrAlY/WC-Co/Cenosphere coatings deposited on MDN 321 steel using atmospheric plasma spraying. Tribological properties of MDN 321 steel and coatings are evaluated from room temperature (RT) to 600 °C under dry lubrication conditions using a pin on disc high-temperature tribometer. Scanning Electron Microscopy (SEM), X-ray diffraction (XRD) and Energy Dispersive Spectroscopy (EDS) are used to characterize the coatings. Presence of cenospheres in these coatings might effectively reduce wear acting as localized regions accumulating wear debris. The result shows that wear rate of all the coatings are lower as compared to MDN 321 substrate at all the test conditions. NiCrAlY/WC-Co/Cenosphere/MoS2/CaF2 and NiCrAlY/WC-Co/Cenosphere/MoS/CaSO4 coatings registered lower friction coefficient as compared to NiCrAlY/WC-Co/Cenosphere coating and MDN 321 substrate. Characterization of the NiCrAlY/WC-Co/Cenosphere/MoS2/CaF2 and NiCrAlY/WC-Co/Cenosphere/MoS2/CaSO4 coatings worn out surface suggests that MoS2 provides lubrication at 200 °C and formation of CaMoO4, MoO3 through tribo chemistry reaction at higher temperature provides lubrication at 600 °C. SEM micrograph of worn surface demonstrates that the main wear mechanism is plowing and delamination.

Nonlinear dynamic behaviour of joint effects on a 2(3PUS+S) parallel manipulator

Clearance, friction, and local elastic and plastic deformation of joint, which can be called joint effects, may cause nonlinear dynamic behaviour of mechanisms. In the paper, nonlinear dynamic behaviour of joint effects on a 2(3PUS+S) parallel manipulator was studied. There are 10 spherical joints in the 2(3PUS+S) parallel manipulator, and the dynamic characteristics of the spherical joints directly affect the overall output performance since they are connected to the moving platforms. Therefore, the joint effects of spherical joint and its effect are studied. To study the effect of the irregular clearance (size of the clearance varies with the attitude) of spherical joint due to manufacturing tolerance and wear, the spherical surface is approximated as an ellipsoid. In addition, the contact force models of spherical joint with variable contact stiffness were established under dry friction and lubrication condition, respectively. And then considering the contact forces of the spherical joints, the overall dynamic model of the 2(3PUS+S) parallel manipulator was established. Based on the overall dynamic model, the influence of joint effects on the dynamic characteristics of the 2(3PUS+S) parallel manipulator was studied, and the correctness of theoretical models was verified through experiments. The results from the simulation and experiments indicate that joint effects can cause nonlinear dynamic characteristics and have important influence on the dynamic performance of the 2(3PUS+S) parallel manipulator.

Influence of Cr addition on tribological properties of bulk Fe2B under dry friction and water lubrication

In the present study, friction and wear properties of bulk Fe2B with different Cr additions were examined under dry friction and water lubrication conditions. The morphology, structure, mechanical properties and tribological properties were investigated by OM, SEM, XRD and XPS. The results show that there is no obvious new phase generated and the crystal structure has no changes with Cr addition. Cr element solubilizes in Fe2B gains without any segregation, only bits of (Fe, Cr)2B crystals formed. With the increasing of Cr addition, the fracture toughness increases first then decreases, and 2Cr sample has the highest toughness. Under dry friction condition, the friction coefficient and wear loss are all decrease first and then increase. 2Cr sample has the highest friction coefficient and wear loss. The tribochemical products form a lubricating film to reduce the friction coefficient and wear loss. And the wear mechanism is mainly brittle fracture. Under water lubrication condition, the friction coefficient drops remarkably, then slightly rises up. In contrast, the wear loss increases first and then decreases. 2Cr sample has the lowest friction coefficient, but the highest wear loss. The wear mechanism is mainly tribo-chemical wear in water. A comparison of the results under dry friction and water lubrication conditions, for the same sample, the friction coefficient is lower, but the wear loss is higher in water.

STATIC FRICTION OF REVERSE STEEL–ELASTOMER SLIDING PAIRS

Sliding cooperation of materials with different hardness (deformability), e.g., a polymeric material cooperating with metallic materials, occurs in machine elements in one of the following two variants: a conventional pair or a reverse pair. In the case of the conventional sliding pair, the deformation area (contact area) of the sliding materials does not move on the surface of the polymer element during their cooperation. In the case of reverse pairs, the contact surface changes its position when moving on the surface of the polymer element. Depending on the variant of the sliding pair, the differences in the friction and wear process of polymer material can be observed. Tribological investigations of chosen sliding pairs (elastomer on steel or steel on elastomer) in the static friction were carried out on the rig. The polymeric materials selected for the tests were thermoplastic elastomers TPU, PUR, and silicone rubber SI. These materials co-operated with C45 steel in the different contact pressures (p = 0.1 – 0.26 MPa) under dry friction or mixed lubrication conditions (hydraulic oil Hipol HLP-68). Based on the recorded value of the friction force Ft, the values of static coefficients of friction μstat were determined. The test results showed a significant influence of the variant of the combination of materials (metal-polymer or polymer-metal) on the value of the friction coefficient. In all tested pairs in which steel sample (pin) slid against elastomeric plates, the friction coefficient was higher than in the case when the elastomeric sample (pins) cooperated with steel counterfaces (plates). The main reason is the considerable value of the deformation component of the friction force. This is probably due to the displacement of the elastomer deformation area in its surface layer and energy dissipation as a result of stress-strain hysteresis in the elastomeric material, as in the case with reversed pairs.

Machinability Study of Developed Composite AA6061-ZrO2 and Analysis of Influence of MQL

Aluminium metal matrix replaces high melting point and high density conventional materials, thus minimizing the usage of energy and supporting the environment. This work develops a low-weight, high-strength composite material with the help of AA 6061 and ZrO2 through a stir casting route incorporated with a squeeze casting setup. Machining and machining tools create impacts on clean environments, as they deal with lubricants and power consumption. Having taken this issue into consideration, this research studies the effect of machining parameters on surface roughness, tool wear, and cutting force, while turning the developed metal matrix composite in dry and minimum quantity lubrication conditions. The turning experiment was performed by designing parameters using an L27 orthogonal array. The turning condition was dry and with minimum quantity lubrication (MQL). The responses obtained in the turning process were analysed using the analysis of variance (ANOVA) technique to find the most influential factor and its percentage contribution. Optimal machining parameters were investigated and tabulated with the help of main effect plots and S/N ratio graphs. Studies prove that there is a linear relationship between MQL versus surface roughness and tool wear, and there was no substantial effect on cutting force.

Microstructure, mechanical and machining properties of LPS and SPS NbC cemented carbides for face-milling of grey cast iron

The effects of spark plasma sintering (SPS), NbC as a major carbide phase and Ni as a Co binder substitute on the microstructure, mechanical properties and cutting insert wear during face-milling of grey cast iron (GCI) BS1452, grade 17, were investigated. Spark plasma sintering refined microstructures increasing the hardness, but lowered the fracture toughness, due to poor binder distribution. Both SPS and liquid phase sintered (LPS) WC based samples had higher hardness than all the NbC based samples. Substitution of Co with Ni in the NbC cemented carbides significantly increased the fracture toughness (by ~5.5MPa·m1/2). During face-milling using inserts produced from the NbC and WC based cemented carbides, the cutting speed (vc) was varied between 100 and 300m/min and the depth of cuts (ap) between 0.5 and 1mm. Face-milling was done under dry and minimum quantity lubrication (MQL) conditions. Wear was evaluated by optical microscopy and high angle annular dark field scanning transmission electron microscopy (HAADF-STEM). The spark plasma sintered NbC1.0-12Co (wt%) insert had lower flank wear rates than the SPS and LPS WC-0.8Cr3C2-12Co inserts in all machining tests, due to the combination of good chemical stability, attrition and abrasion wear resistance from the refined microstructure. The lower flank wear rate was also attributed to the shorter chamfer width. Use of MQL at a vc of 300m/min and ap of 0.5mm, reduced the cutting temperatures, but increased the cutting force and flank wear rates of all the inserts.

Investigating tool wear mechanisms in machining of Ti-6Al-4V in flood coolant, dry and MQL conditions

The objective of this study is to identify and explain tool wear mechanisms that dominate during machining of titanium alloy Ti-6Al-4V in dry, flood coolant, and minimum quantity lubrication (MQL) conditions. A series of experiments were conducted using end milling of Ti-6Al-4V by varying feed rate and depth of cut, while the cutting speed was kept constant at comparatively higher cutting speed. Both uncoated and titanium aluminum nitride (TiAlN)-coated carbide tools were used for machining Ti-6Al-4V at the same settings of parameters. It was observed that abrasion was the most dominant tool wear mechanism for all dry, flood coolant and MQL machining conditions. Edge chipping and tool nose wear were the next dominating tool wear mechanisms in conventional flood coolant machining, which may be associated with the thermal fatigue caused by the periodic cooling of tool tip from the high temperature generated during machining. On the other hand, adhesion was the second most dominant tool wear mechanism in the dry machining. Both the edge chipping and adhesion of chips to the cutting tools were reduced significantly in MQL machining. The delamination of coating film was observed when TiAlN-coated carbide tools were used for machining Ti-6Al-4V. The delamination was more significant in wet and MQL machining compared to dry machining, indicating the effectiveness of coated tools in dry machining condition compared to wet and MQL machining conditions. Among three conditions, MQL provided the least occurrences of tool wear, indicating suitability of MQL in productive machining of titanium alloys.

ANFIS modeling to predict the friction forces in CNC guideways and servomotor currents in the feed drive system to be employed in lubrication control system

In this research work, Adaptive Neuro-Fuzzy Inference System (ANFIS) modeling is implemented to predict the friction force in the CNC linear guideways and servomotor current in the feed drive system in dry lubrication condition. Initially, the friction forces in the CNC linear guideways are calculated from the cutting force analysis during cutting in dry lubrication condition. Second, the servomotor currents on the X and Z-axes are measured during cutting in the same condition. Finally, ANFIS modeling to predict the friction force in CNC linear guideways and servomotor current is established using the training data obtained from cutting. Furthermore, the ANFIS prediction error and accuracy for both friction force and servomotor currents are investigated. The results demonstrate that the proposed ANFIS model can predict friction forces and servomotor currents with 1.38% and 4.1% errors, respectively. The low error percentages indicate that ANFIS modeling can be employed in a new technique for a lubrication control system for green manufacturing.

Tribological Characteristics of MoS2 and DLC Film in Sliding Contacts under Dry, Lubricant and Grease Lubrication Conditions

The objective of this study is to investigate the effect of solid and liquid lubrication on friction and wear performance of selected solid lubricating coatings, comparative experiments have been carried out on magnetron sputtered MoS2 coatings and chemical vapor deposited hydrogenated diamond-like carbon (DLC) films against Si3N4 ball using a ball-on-disk tribo-tester under the conditions of room temperature and different lubrication condition. Surface morphology of coatings was investigated by atom force microscope (AFM), and friction coefficient (COF) and, wear rate of solid films was also analyzed. It was shown that the friction was greatly reduced when the solid film which was lubricated with oil and grease was simultaneously compared and lubricated singly at the start-up or under boundary lubrication conditions. Liquid lubrication causes a dramatic decrease of the wear-ability to the MoS2 coatings, while the wear rate of DLC film was improved better. The effect of lubrication oil to the wear resistance property of MoS2 film was worse than lubrication grease, which was opposite to the DLC film.

Influence of Pelvis Width and Leg Length on the Wear Behavior of UHMWPE Hip Cup

Total hip joint replacement considered one of the success sections of the modern medicine, but still the wear of total hip prostheses is a significant clinical problem and this problem might be increasingly complex with adding the influence of pelvis width and leg length during the preclinical testing. This study aims to analyze the effect of the leg length (femur and tibia) and the pelvis width on the wear behavior of ultra-high molecular weight polyethylene (UHMWPE) hip cup. The experiments have been carried out on a total leg joint’s simulator (TLJS), which was particularly designed for this purpose according to ISO 14242-1 standard. The TLJS consists of three units: leg components (femur, tibia, and foot), quick-return mechanism, and cam mechanism were used to reproduce the flexion–extension and external–internal movement, respectively, and upper body was used to stimulate the pelvis construction and applied load. The wear behavior of the tested cups (in weight loss form) was evaluated under dry lubricating conditions, and then the wear mechanism of worm cups was examined by using scanning electron microscopy. The results showed that the length of the femur, tibia, and pelvis width have a positive effect on the wear rate of the tested cups due to flexion and pelvic moment which is resulted by the ground reaction force and pelvic rotation force.

Tribological behavior of polyimide/epoxy resin-polytetrafluoroethylene bonded solid lubricant coatings filled with in situ-synthesized silver nanoparticles

Abstract Polyimide/epoxy resin-polytetrafluoroethylene (denoted as PI/EP-PTFE) bonded solid lubricant coatings filled with silver nanoparticles synthesized in situ were prepared. The phase composition and grain size of the Ag nanoparticles were analyzed by X-ray diffraction and field-emission scanning electron microscopy, respectively. A micro-hardness tester was employed to determine the micro-hardness of the as-fabricated PI/EP-PTFE lubricant coatings, and a ring-on-block test rig was selected to evaluate the tribological behavior of the lubricant coatings under dry friction and RP-3 aviation kerosene lubrication conditions. The worn surfaces of the lubricant coatings were observed with a scanning electron microscope. Results indicate that the silver citrate precursor was decomposed to generate Ag nanoparticles during the curing process of PI/EP-PTFE lubricant coatings. Resultant in situ-synthesized Ag nanoparticles with a size of about 100 nm were homogeneously dispersed in the lubricant coatings, thereby significantly increasing the micro-hardness, reducing the friction coefficient and enhancing the wear life of the lubricant coatings. Particularly, the lubricant coating filled with 5% Ag nanoparticles exhibited the lowest friction coefficient and the longest wear life. Moreover, due to the excellent lubrication and cooling effect of RP-3 aviation kerosene, the lubricant coating achieved better friction-reducing and anti-wear abilities under RP-3 aviation kerosene lubrication than that under dry friction.

An experimental study on end milling of titanium alloy (Ti-6Al-4V) under dry and minimum quantity lubrication conditions

This paper presents the results of an optimisation study of low speed machining of Ti-6Al-4V alloy by technique of order preference by similarity to ideal solution (TOPSIS). End milling was conducted under dry and minimum quantity lubrication (MQL) conditions and at different levels of cutting speed (20 to 40 m/min), feed (0.05 to 0.15 mm/rev) and axial depth of cut (0.4 to 1.2 mm) using a full factorial design. Machinability was evaluated by measuring surface roughness and cutting forces. The micro-hardness below the machined surface for some selected combinations of cutting conditions was also measured. It was found that the feed per rev and depth of cut have the greatest influence on cutting forces and surface roughness under dry and MQL conditions. The minimum cutting forces and minimum surface roughness are obtainable at cutting speed of 30 mm/min, feed of 0.05 to 0.1 mm/rev and depth of cut of 0.4 mm under MQL condition. It was also found that these conditions result in the minimum alteration of micro-hardness beneath the machined surface.

An experimental study on end milling of titanium alloy (Ti-6Al-4V) under dry and minimum quantity lubrication conditions

This paper presents the results of an optimisation study of low speed machining of Ti-6Al-4V alloy by technique of order preference by similarity to ideal solution (TOPSIS). End milling was conducted under dry and minimum quantity lubrication (MQL) conditions and at different levels of cutting speed (20 to 40 m/min), feed (0.05 to 0.15 mm/rev) and axial depth of cut (0.4 to 1.2 mm) using a full factorial design. Machinability was evaluated by measuring surface roughness and cutting forces. The micro-hardness below the machined surface for some selected combinations of cutting conditions was also measured. It was found that the feed per rev and depth of cut have the greatest influence on cutting forces and surface roughness under dry and MQL conditions. The minimum cutting forces and minimum surface roughness are obtainable at cutting speed of 30 mm/min, feed of 0.05 to 0.1 mm/rev and depth of cut of 0.4 mm under MQL condition. It was also found that these conditions result in the minimum alteration of micro-hardness beneath the machined surface.

Optimization and Influence of Process Parameters on Surface Roughness in Turning of Titanium Alloy under Different Lubricant Conditions

In any machining process, large amount of heat is generated due to plastic deformation of work material, friction at the tool – chip and tool - work piece interface. In dry machining, the heat generated adversely affects the quality of the products. Therefore, effective control of heat generated in the cutting zone is essential to ensure good surface quality of the work piece in machining. Cutting fluids have been the conventional choice to deal with this problem. Cutting fluids are introduced in the machining zone to improve the tribological characteristics of machining processes and to dissipate the heat generated. The advantages of cutting fluids however been questioned later on due to the negative effects on product cost, environment and human health. Later on Minimum Quantity Lubrication (MQL) has been tried as a possible alternative to the use of flooded coolants. Minimum Quantity Lubrication machining refers to the use of a small amount of cutting fluid, typically in order of 300 ml/hr or less, which are about three to four orders of magnitudes lower than that used in flooded lubricating conditions.This paper deals with the optimization and influence of process parameters on surface roughness in turning of Ti-6Al-4V alloy under dry, flooded and Minimum Quantity Lubrication (MQL) conditions using Taguchi’s robust design methodology. The results have been compared among dry, flooded and MQL conditions and it reveals that MQL shows better performance and improvement in reduction of surface roughness as compared to dry and flooded lubricant conditions. The CVD coated tool shows better performance as compared to the uncoated and PVD coated tools. It is also observed from the ANOVA that, feed rate has major influence on surface roughness.

Experimental study of the tribological properties of an elevator’s brake linings

Purpose This paper aims to design and manufacture a wear-test rig performing reciprocating movement that is more relevant to the elevator brake system. Also, a sample test result that was conducted in this experimental set-up is presented to evaluate the tribological properties of the brake linings of the elevator system that are activated in emergencies. Design/methodology/approach The brake linings are some of the most important security elements in elevators. The friction and wear properties of these brake linings have great importance for both safety and comfort. Elevator brake linings are often used in conjunction with guided rails under dry and boundary lubrication conditions. Therefore, friction coefficient and wear types occurring in the brake linings may be different. The tribological properties of the brake lining material in the literature are generally identified using a pin-on-disc wear-tester. The pin is contacted by rotating a disc in this wear-test rig. However, as the brake linings and guide rails do not have a reciprocating movement (linear translational motion) on each other, this wear-test rig is not suitable for brake linings and guide rails in the elevator system. Findings A sample test result that was conducted in this experimental set-up is presented to evaluate the tribological properties of the brake linings of the elevator system that are activated in emergencies. In these experiments, three different brake lining materials that are widely used in the elevator car guide rails in Turkey were tested under different speeds and loads. Originality/value The paper provides information about how to evaluate the tribological properties of the brake linings of the elevator system that are activated in emergencies. Also, it offers practical help for the manufacturer and researcher in the elevator sector.

Optimization of MQL flow rate for minimum cutting force and surface roughness in end milling of hardened steel (HRC 40)

The present work focuses on the performance modeling of hard milling to attain an optimum parameter setting for the minimum cutting force and surface roughness. Furthermore, it was attempted to compute the minimum quantity lubricant flow rate precisely, besides the cutting speed and table feed rate, by adopting Grey-based Taguchi method and composite desirability function. The experimental data was collected by end milling of hardened AISI 4140 steel using carbide cutter under dry and minimum quantity lubrication conditions according to Taguchi L 16 orthogonal array. The predictive model of the responses was formulated by using response surface methodology. The analysis of variance revealed that the table feed has the maximum influence on cutting force, and the flow rate of lubricant has the highest effect on surface roughness. The parameter setting at lower table feed, higher cutting speed, and 150-ml/h lubricant flow yield the minimum value of the responses. Finally, the results of confirmation test verified the adequacy and supremacy of the optimization models; however, Grey-based Taguchi method induced a better optimization.

Investigation of flank wear in MQL milling of ferritic stainless steel by using nano graphene reinforced vegetable cutting fluid

Purpose In milling of stainless steel materials, various cutting tool failures such as flank wear, crater wear, cracks, chipping, etc. can be observed because of their work hardening tendency and low thermal conductivity. For this reason, this paper aims to develop some coolants and coatings to reduce these formations. However, further research should be performed to reach the desired level. Design/methodology/approach In this study, the initial flank wear rates of uncoated and titanium nitride-coated tungsten carbide cutting tools were investigated during the milling of AISI 430 ferritic stainless steel. The milling experiments were conducted under dry and minimum quantity lubrication (MQL) conditions. Nano graphene reinforced vegetable cutting fluid was prepared and applied by the MQL system. The mixture ratios of nanofluids were selected as 1 and 2 wt.%, and MQL flow rates were adjusted at 20 and 40 ml/h. Findings It was observed that MQL milling with nano graphene reinforced cutting fluid has advantages over dry milling and MQL milling with pure cutting fluid in terms of the initial flank wear. Originality/value This paper contains new and significant information adequate to justify publication. MQL is a new method for vegetable cutting fluid containing nano graphene particles.

Cutting force analysis to estimate the friction force in linear guideways of CNC machine

Linear guideways are widely applied in advanced machinery industries worldwide for different types of CNC machine (e.g., turning, milling, grinding, and gantry). All of these machines require accuracy and precision in the machining operations to manufacture quality products. The cutting operation in product manufacturing occurs with the displacement of machine tables on linear guideways. For this reason, linear guideways are significant parts and have sensitive locations in CNC machines to yield precision and accuracy. Friction is a major factor of deformation in guideways and non-smooth motion that prevents superior accuracy and precision in machine operations. Moreover, the frictional behavior in linear guideways is one of the most crucial challenges for CNC machining, such that between two parts of friction and temperature stimulus there will be stick-slip motion, wear and corrosion of the parts. Thus, manufacturers are interested in these machines, particularly to facilitate this process with an actual lubrication system. Hence, friction force estimation and modeling in CNC machine guideways is used to overcome these problems by controlling the lubrication operation.In this research work, the cutting force components including, longitudinal force (FL), radial force (Fr) and tangential force (Ft) are measured during cutting process. These cutting force values are corresponding to different cutting conditions includes, spindle speed, depth of cut, and feed rate. The cutting force components and the weight of the moving parts are analyzed and transferred to the CNC machine guideways. The friction force on linear guideways of machine tools is modeled based on the analyzed and transferred force components on the guideways during cutting. The static and kinetic coefficient of friction are measured experimentally in dry lubrication condition hence the friction force components can be obtained. The friction force are estimated using the identified coefficient of friction.

Experimental investigation of the tool wear in micro-milling of stainless steel 316

The objective of this paper is to experimentally investigate the micro-machinability of stainless steel 316 under both dry and minimum quantity lubrication conditions. The machinability was assessed in terms of tool wear, tool life, cutting forces and surface finish. The tool life was characterised as the amount of material removed, instead of the conventional cutting times. The machining performance under MQL is superior to the dry machining for both process conditions in terms of the tool life. The magnitude of the machining forces showed cyclic pattern for both MQL and dry machining. The SEM images and the cutting force signals suggested that the dominant mode of the tool wear in micro-milling is edge chipping and abrasive wear at the tool tip. The surface roughness at the bottom of the slots improved significantly with the application of MQL for all levels of the tool wear.

The Effects Of Friction On Stamping Process Of Sheet Metals Used In Aviation

Abstract An important factor in the possibility of obtaining correct drawn parts with the desired functional properties is the friction between the stamped sheet and the tool. The article discusses the impact of technological lubricants developed according to our own formulas, based on vegetable oils, on the stamping process taking into account the strain distributions in the drawn parts. Biodegradable lubricants based on rapeseed oil with an addition of stearic acid or boric acid were used. The results of the friction coefficient in a strip drawing test and the numerical analysis results of the stamping process of a spherical cap from sheet metal: aluminium 2024, commercially pure titanium Grade 2, steel 5604 in dry friction and lubrication conditions, are presented. Strain distributions and changes in the drawn part wall thickness were analysed.