Lubrication Environment Research Articles

Mechanical and friction behavior of sputtered Mo–Cu–(N) coatings under various N2 gas flow using a multicomponent single alloy target

Mo–N based coatings have attracted increasing attention as protective coatings for mechanical components owing to their superior mechanical performance. In this study, ternary (binary) Mo–Cu–(N) nanocomposite coatings are prepared at various N2 gas flow rates by direct current magnetron sputtering using a multicomponent single alloy target. The microstructure, morphology, mechanical properties, and friction behavior of the coatings are characterized. The friction and wear behavior of the coatings prepared at various nitrogen gas flow rates are measured under different lubricant environments such as 5W30 with MoDTC additive and polyalphaolefin. The composition of the coatings is found to be nearly similar to that of the target regardless of the nitrogen content, but the microstructure showed significant changes. In this study, Mo–Cu–(N) nanocomposite coating obtained under N2 gas flow rate of 6 sccm exhibits the best mechanical property and friction performance under harsh environments (100 N, 150 °C) owing to the presence of hard MoxN phase with a grain size of approximately 6.43 nm and Cu phase. The extremely low friction coefficient of 0.003 is attributed to the interaction of the coating and oil/counterpart components during the friction test under the polyalphaolefin lubricant environment.

Cutting Parameter Optimization in Finishing Milling of Ti-6Al-4V Titanium Alloy under MQL Condition using TOPSIS and ANOVA Analysis

Titanium and its alloys give immense specific strength, imparting properties such as corrosion and fracture resistance, making them the right candidate for medical and aerospace applications. There is a wide range of engineering applications that use titanium alloys in a variety of forms. The cost of these alloys is slightly higher in comparison to other variants due to the problematic extraction of the molten process. To reduce costs, titanium alloy products could be made by casting, isothermal forging, radial swaging, or powder metallurgy, although these techniques require some kind of finishing machining process. Titanium and its alloys are difficult to machine due to skinny chips leading to a small cutting tool-workpiece contact area. The thermal conductivity of titanium alloys is too low and the stress produced is too large due to the small contact area, which results in very high cutting temperatures. This paper deals with the experimental study of the influence of the Minimum Quantity Lubricant (MQL) environment in the milling of Ti-6Al-4V alloy considering the optimization of surface roughness and production rate. Taguchi-based TOPSIS and ANOVA were used to analyze the results. The experimental results show that MQL with vegetable oil is successfully applied in the milling of Ti-6Al-4V. The research confirms the suitability of TOPSIS in solving the Multiple Criteria Decision Making (MCDM) issue, by choosing the best alternative at Vc=120m/min, fz=0.065mm/tooth, and ap=0.2mm, where the surface roughness and material removal rate are 0.41µm and 44.1492cm3/min respectively. Besides, ANOVA can be used to predict the best parameters set in the milling process based on the regression model. The parameters predicted by ANOVA analysis do not coincide with any implemented parameters

Optimization of process parameters for turning of titanium alloy (Grade II) in MQL environment using multi-CI algorithm

The advancement of materials science during the last few decades has led to the development of many hard-to-machine materials, such as titanium, stainless steel, high-strength temperature-resistant alloys, ceramics, refractories, fibre-reinforced composites, and superalloys. Titanium is a prominent material and widely used for several industrial applications. However, it has poor machinability and hence efficient machining is critical. Machining of titanium alloy (Grade II) in minimum quantity lubrication (MQL) environment is one of the recent approaches towards sustainable manufacturing. This problem has been solved using various approaches such as experimental investigation, desirability, and with optimization algorithms. In the group of socio-inspired optimization algorithm, an artificial intelligence (AI)-based methodology referred to as Cohort Intelligence (CI) has been developed. In this paper, CI algorithm and Multi-CI algorithm have been applied for optimizing process parameters associated with turning of titanium alloy (Grade II) in MQL environment. The performance of these algorithms is exceedingly better as compared with particle swarm optimization algorithm, experimental and desirability approaches. The analysis regarding the convergence and run time of all the algorithms is also discussed. It is important to mention that for turning of titanium alloy in MQL environment, Multi-CI achieved 8% minimization of cutting force, 42% minimization of tool wear, 38% minimization of tool-chip contact length, and 15% minimization of surface roughness when compared with PSO. For desirability and experimental approaches, 12% and 8% minimization of cutting force, 42% and 47% minimization of tool wear, 53% and 40% minimization of tool-chip contact length, and 15% and 20% minimization of surface roughness were attained, respectively.

Performance Evaluation of Al-SiC Nanofluids Based MQL Sustainable Cooling Techniques During Turning of EN-24 Steel

The conventional cutting fluids are used in metal cutting processes for cooling and lubrication. However, the use of cutting fluids is creating the environmental and biological problems. In order to minimize these problems, it is essential to move towards sustainable cooling techniques. The present investigation determine the influence of sustainable cooling techniques such as cryogenic cooling, minimum quantity lubrication, Al2O3/soluble oil nanofluids based minimum quantity lubrication, SiC/soluble oil nanofluids based MQL and Al-SiC/soluble oil hybrid nanofluids based minimum quantity lubrication on output characteristics during turning of EN-24 steel. For experimentation nanofluids were formulated with accumulation of different weight percentages (0.5wt.%, 1.0wt.%, 1.5wt.%) of Al2O3, SiC and Al-SiC nanoparticles to the soluble oil. The thermal and tribological properties of Al2O3/soluble oil nanofluids, SiC/soluble oil nanofluids and Al-SiC/soluble oil hybrid nanofluids were analyzed. Individual machining performance such as surface roughness height, tool wear and specific energy lead to ambiguous understanding. So, the cumulative performance index is also calculated. The cumulative performance index is used to determine the performance of different sustainable cooling techniques during turning of EN-24 steel. The experimental results revealed that the turning performance of EN-24 steel under Al-SiC/soluble oil hybrid nanofluids based minimum quantity lubrication environment is superior then other machining environments.

Sustainability assessment of difficult-to-cut materials using rotary tools: a step towards sustainable machining environment

Difficult-to-cut materials offer superior properties such as high chemical stability, strength-to-weight ratio, and corrosion resistance. However, machining these materials is facing huge challenges due to localized high levels of temperature, especially when using traditional tools. Machining using rotary tools is a suitable technique that is used to machine difficult-to-cut materials which provides acceptable tool life, even under dry conditions. Rotary tools offer significant improvements compared to conventional tools especially in dry conditions, which makes this technology a good candidate to achieve a sustainable machining environment. Despite all attempts in modeling, analysis, and optimization of machining using rotary tools, it was found that no previous study has focused on the sustainability aspects related to the application of rotary tools in machining operations. Thus, in the current work, an attempt has been made to assess and prove the effectiveness of machining with rotary tools. Two different case studies are presented and discussed to evaluate and assess the sustainability effectiveness of rotary tools compared to stationary ones under different cooling and lubrication environments (i.e., flood, minimum quantity lubrication (MQL), and dry). The results showed that machining using SPRT under dry conditions provided higher total weighted sustainability index compared to the traditional approach for both case studies. Finally, a detailed mechanism for machining with a rotary tool is fully presented and discussed to physically prove the sustainability effectiveness of such technology. It was concluded from the sustainability assessment results that using self-propelled rotary tools under a dry environment showed significant results which proved the applicability of using rotary tools as a sustainable technology.

Experimental analysis of process parameters in drilling nimonic C263 alloy under nano fluid mixed MQL environment

Nimonic C263 is a super alloy and it is difficult to cut. As this alloy possess high proportion of chromium, cobalt, and molybdenum, which fortify the material by solution hardening, which inhibits the dislocation movement, resulting in higher plastic deformation. In this research, an attempt has been made to model, analysis and investigate the machining characteristics such as thrust force, temperature at drill cutting edge, flank wear and surface finish during drilling of this alloy using silver nano fluid mixed Minimum Quantity Lubrication (MQL) environment. Residual stress at various combinations of process parameters was also observed and discussed. RSM based empirical models of the process parameters and optimization of multi response was developed. Thrust force, Temperature at drill cutting edge, surface roughness and tool wear affected by feed rate (percentage of contribution-60%), spindle speed (percentage of contribution-88.63%), spindle speed (percentage of contribution-71.42%) and feed rate (percentage of contribution-67.76%) respectively followed by other parameters.

CFD-Based Investigation of Lubrication and Temperature Characteristics of an Intermediate Gearbox with Splash Lubrication

In this study, we propose a computational fluid dynamics (CFD)-based method to study the lubrication and temperature characteristics of an intermediate gearbox with splash lubrication. A volume of fluid (VOF) multiphase model was used to track the interface between oil and air. A multiple reference frame (MRF) model was adopted to accurately simulate the movement characteristics of the gears, bearings, and the surrounding flow field. The thermal-fluid coupling computational model of an intermediate gearbox with splash lubrication was then established. Combined with experimental results, we verified that the lubricating oil temperature was below the limit requirement (<110 °C). The numerical results revealed that large amounts of lubricating oil were splashed onto the tooth surfaces near the gear meshing area. A large convective heat transfer coefficient corresponds to a low gear tooth surface temperature. The tooth surface temperature of the driving gear is higher than that of the driven gear. The distribution law of oil volume fraction of the bearing roller was jointly affected by the roller rotation direction and gravity. The convective heat transfer coefficient of the roller wall was largely related to the lubrication environment of the roller, including the oil distribution inside the bearing cavity and the flow rate.

Predicting forming limit diagrams for AZ31 magnesium alloy and 7050 aluminum alloy by numerical simulation

Forming limit diagram (FLD) is the most intuitive method to evaluate and analyze the forming performance of sheet metal, which is widely used in production. To examine the formability of AZ31 magnesium alloy and 7050 aluminum alloy, the simplified bulging models based on the Nakazima experiment are established by ABAQUS finite element (FE) software, and the maximum punch force criterion is adopted as the instability criterion. The forming limit diagrams of 7050 high-strength aluminum alloy at room temperature and AZ31 magnesium alloy at warm working conditions are obtained by extracting the in-plane strain of the adjacent element of the maximum strain element at the moment of instability. Compared with experimental observation shows that the Nakazima virtual model established in this paper can accurately predict FLD. In addition, the influences of lubrication conditions and virtual punching speeds on the bulging process of AZ31 and AA7050 sheet metals are also investigated. The results show that the better the lubrication environment, or the lower the punching speed, the better the formability of the sheet, and reducing the punching speed has a more significant improvement effect on the formability of AZ31 sheets.

Tool Wear and Temperatures Analysis While Machining Ti-6Al-4V in MQCL-MIST Environment

Sustainable machining of titanium alloys have deficiency of studies on the built-up edges over the cutting tools and temperature correlation in minimum quantity cooling lubrication (MQCL) environment. Researchers focused on experimentation in dry, wet, and MQL (minimum quantity lubrication) conditions to analyze surface finish, cutting forces, and metal removal rates. This work focuses on the study of cutting parameters effects on temperatures and tool wear analysis by consideration of individual response and their optimality basing on signal-to-noise ratios. Efficacy of process parameters on wear of tool and temperatures requires a comprehensive understanding. An elaborated tool wear analysis is carried based on the microscopic flank wear investigations. Machining of Ti-6Al-4V alloy is carried in the environment of MQCL in form of mist using semi-synthetic fluid. Correlation study of tool wear with regard to temperatures is analyzed and regression models generated on tool wear and cutting temperatures individually showed 83% of goodness-of-fit and correlation regression is 85%.

Studies on chip morphology and modes of tool wear during machining of Ti-6Al-4V using uncoated carbide tool: application of multi-walled carbon nanotubes added rice bran oil as nanocutting fluid

In this work, machining performance of Ti-6Al-4V is studied in consideration with cutting force, tool-tip temperature, tool wear mechanisms, chip morphology and roughness of the machined surface. Machining experiments are carried out by varying cutting speed (Vc) with constant feed and depth-of-cut. Uncoated WC-Co insert is used as cutting tool. Multi-walled carbon nanotubes (MWCNTs) added rice bran oil is utilized to produce nanofluid minimum quantity lubrication (MQL) environment. Chip morphology along with measurable geometrical parameters including chip-tool contact length, equivalent chip thickness (H ch), segmentation spacing, segmentation frequency, shear band width, shear angle, chip hardness, etc. are studied in detail. Effects of Vc on cutting force, tool-tip temperature, depth of flank wear, and area of crater wear are discussed. Different tool wear mechanisms are identified as well. It is experienced that nanofluid MQL (NFMQL) outperforms traditional dry cutting as well as conventional MQL in purview of improved process performance.

Progress for sustainability in the mist assisted cooling techniques: a critical review

The proper implementation of sustainable manufacturing processes is an effective step towards a clean environment. The modern cooling strategies applied in the manufacturing sector have presented promising solutions that enable economic growth and ecological environment. In machining operations, cryogenic cooling and minimum quantity lubrication (MQL) have been extensively utilized to replace conventional cooling techniques. Thus, this work offers a detailed review of major works focused on manufacturing processes that use some of these sustainable cooling/lubrication modes (i.e., MQL, nanocutting fluids, nanofluid-based MQL strategy, and other miscellaneous MQL upgrades). The main driver of this study is to create a bridge between the past and present studies related to MQL and MQL upgrades. In this way, a new guideline can be established to offer clear directions for a better economic vision and a cleaner manufacturing process. Thus, this review has mainly focused on the machining of the most commonly used materials under MQL-related methods in conventional operations including turning, milling, drilling, and grinding. Current work provides a detailed insight into the major benefits, limitations, as well as mechanisms of cooling strategies that directly affects the machinability performance from a sustainable point of view. In summary, further potential upgrades are indicated so that it will help to drive more sustainable approaches in terms of cooling and lubrication environment during machining processes.

Experimental investigation on Stribeck curves of different elastic modulus materials under oil and water lubrication conditions

Purpose The purpose of this paper is to study the influence of friction coefficient of materials with different elastic modulus on the variation of velocity and load under water lubrication and oil lubrication conditions. Design/methodology/approach Low-viscosity lubricating oil and water were used as lubricants to test the friction performance of the ball-disc contact friction pair in the lubrication state on the universal micro-tribometer multi-functional friction and wear test system. Findings In the same speed range, the lubrication states from soft to rigid materials are not necessarily similar to each other. Generally, the material with low elastic modulus is suitable in low-viscosity lubricant environments, while the material with high elastic modulus has relatively smaller friction coefficients in oil-lubricated environments compared with water lubrication. However, the coefficients of polyethylene, polytetrafluoroethylen and polyoxymethylene are exceeded by rubber’s coefficients under water lubrication in the same experiment environments, and their lubrication states are not affected by lubricants. The friction coefficient of the friction pair decreases with the increase of loads; however, it does not apply to all materials. The friction coefficients of materials with smaller elastic modulus such as rubber under high loads are rather large. Therefore, the elastic modulus of the material under high loads is a factor to be considered. Originality/value The Stribeck curves study of the ball-disk contact friction pair comprising soft and rigid materials, whose elastic modulus is from hundreds of GPa to a few of MPa, was carried out. The influence of different speeds, loads and lubricants on the friction coefficient of the friction pair was revealed, which provided a research basis for the selection and matching of friction pair materials.

Tuning C–C sp2/sp3 ratio of DLC films in FCVA system for biomedical application

Diamond like carbon (DLC) films with different C–C sp2/sp3 ratios were prepared by tuning the N2 flow rate in a filtered cathodic vacuum arc (FCVA) system. The increase of N2 flow rate facilitated the increase of C–C sp2/sp3 ratio (1.09–2.66), the growth of particle size (0.78–1.58 nm) and the improvement of surface roughness. The SBF immersion results, as well as WCAs (77.57°~71.71°), hemolysis rate (0.14–1.00%) and cytotoxicity level (0) demonstrated that the as-fabricated DLC film was promising for biomedical application. As a result of surface charge effect, the apatite layers formed in the SBF increased with the increase of C–C sp2/sp3 ratio until 1.74 and then showed a tiny decrease during 1.74–2.66. A raise of hemolysis and cytotoxicity was observed when sp2/sp3 ratio was increased. Moreover, a decrease of friction coefficient of Si surface induced by increasing sp2/sp3 ratio was respectively evidenced in ambient air and SBF lubrication environments.

Stable lubrication in air and vacuum of GO-Al3+ coating via strong chemical bonding and reactive sites passivation by aluminum ions

Graphene oxide (GO), as a layered two-dimensional nanomaterial, is usually considered as potential candidate of solid lubricant because of its unique physical, chemical, and mechanical properties. However, its tribological behaviors strongly relate to the lubrication environment and the interlayer bonding strength. In this work, a bio-inspired GO-Al3+ coating with nacre-like layer-by-layer compact structure is constructed by using aluminum ions (Al3+) as the cross-linkers. As a comparison, a GO-spin coating with the same thickness is also fabricated by means of spin coating technique. The results show that the lubrication performance of the GO-spin coating is strongly dependent on the environment conditions; namely, it has good lubrication property in air while fails in vacuum due to the lack of passivating species. For the GO-Al3+ coating, the introduction of Al3+ passivates the reaction sites on GO sheets, preventing lubrication failure of GO coating in vacuum. Besides, the introduction of Al3+ dramatically enhances the interlayer bonding strength of coating, which results in high efficiency of load transfer and improved mechanical properties, therefore reducing wear loss with a thinner transfer film both in air and vacuum environments.

Influence of process parameters on the ultrasonic assisted edge trimming of aerospace CFRP laminates using MQL

The use of carbon fibre reinforced plastic (CFRP) composites is increasing rapidly especially in applications demanding high performance such as aerospace structural components. Edge trimming of CFRP parts is essential for controlling the dimensional tolerances and/or the product quality to meet the industrial standards or specification. This article investigates the ultrasonic-assisted edge-trimming of multidirectional CFRP laminates in minimum quantity lubricant (MQL) environment. Statistical analysis was conducted to assess the effect of process parameters on the performance indicators. Cutting speed, feed rate, and radial depth of cut were selected as process parameters while the key performance characteristics were cutting forces, bouncing-back, material removal rate (MRR), and surface integrity in terms of surface roughness (Ra, Rz) as well as delamination. The most significant process parameter affecting each performance characteristic was determined using ANOVA test. Regression equations were also developed to predict the magnitude of bouncing back and MRR.

MQL machining of high strength steel: A case study on surface quality characteristic

The present paper highlights investigation on hard turning of high strength EN24 steel using multilayer coated carbide insert (TiN/TiCN/Al2O3/ZrCN) under minimum quantity lubrication environment for surface roughness. Measured surface values are found to be less than 1 µm which is much below the surface roughness criteria of 1.6 µm. It indicates that quality components can be obtained during MQL assisted machining of high strength EN 24 steel. This indicates proper cooling and lubrication of machining zone occurred due to application of pressurized oil mist. Developed regression model has been found to be significant because determination coefficient i.e. R2 close to unity (0.9) and p-value is less than 0.05 at 95% confidence level. Hence, environmental friendly minimum quantity lubrication machining can be effectively utilized for production of quality components in industrial shop floors for ecological and economical benefits.

Machinability studies on aluminium matrix nanocomposite under the influence of MQL

Abstract The overwhelming rise in pollution led to the enforcement of stern measures to restrict certain techniques and served a path to the development of alternate methods. Although aluminium hybrid composites were significantly seen in automobile and aerospace industries due to their enhanced thermal and mechanical properties, its machining is proven to be challenging. In this study, squeeze cast cylindrical workpieces are made out of unreinforced aluminium alloy and aluminium alloy-based hybrid nanocomposite. They are machined by varying the cutting speed, feed rate and depth of cut under dry and minimum quantity lubrication environments. The impact on cutting forces, surface roughness and tool wear are observed and compared and presented in this study

An Experimental and Numerical Approach to Study the Performance of Modified Perforated Cutting Tools on Machining of Ti–6Al–4V Alloy

In this research, the main aim is to reduce the unfavorable effects that occurred during machining of the Ti–6Al–4V alloy by perforating the rake face and the flank face of the cutting insert. The main novelty in this research is that machining of Ti–6Al–4V alloy with the micro-hole textured insert helps in the improvement of tribological properties and also reduces cutting temperature at chip–tool interface with proper lubricating effect. To validate the micro-hole textured tools, it is compared with conventionally available insert. The deformation of Ti–6Al–4V alloy with modified cutting inserts was simulated, considering tool as rigid body and workpiece as elasto-plastic material. DEFORM 3D software was used for the simulation of the machining process with the updated Lagrangian formulation. To predict the cutting temperature and chip morphology, the thermo-mechanical analysis was applied using Johnson–Cook material model for the machining process. The turning of the Ti–6Al–4V alloy was carried out with the modified polycrystalline diamond (PCD) cutting inserts (Design 1 and Design 2) and commercially available PCD insert (normal insert). Coconut oil was used as a micro-pool lubricant during the machining process under minimum quantity lubrication environment. In the present work, the turning performance characteristics such as cutting temperature, cutting vibration, tool wear, chip morphology and surface integrity were measured during machining of the Ti–6Al–4V alloy. The experimental results of cutting temperature and chip morphology were validated with the simulation results with better accuracy. The machining results of Design 2 cutting insert showed maximum reduction of 30%, 38%, 45% and 35% in cutting temperature, cutting vibration, tool wear and surface roughness, respectively, when compared with machining under normal insert and Design 1 cutting insert. It is also evident from the results that machining with Design 2 cutting insert significantly improved the process performance of the product quality at higher feed rates.

Performance comparison of dry, flood and vegetable oil based minimum quantity lubrication environments during CNC milling of Aluminium 6061

Abstract The minimum quantity lubrication in machining has been emerged as the sustainable manufacturing techniques and being widely explored for industrial applications since last few years. The aim of this paper is to explore the CNC milling performance while machining Aluminium 6061 under three different environments viz. dry, flood and vegetable oil based minimum quantity lubrication (MQL) technique. Taguchi L9 array was used to design the experiments, for three machining input parameters viz. cutting speed, feed rate and depth of cut; considering the efficient use of limited resources. A fresh TiAlN coated carbide PVD insert was used in end milling of Aluminium 6061T6 for each experimental run. A total of 27 experiments were performed for dry, flood and MQL environments. Average surface roughness was analysed for each experiment and machining parameters for better surface finish were optimized. It was observed that MQL provides the best surface finish out of all three cooling environments. Tool wear was also found to be reduced significantly in MQL environment as compared to dry and flood techniques. It was concluded that MQL cooling technique can be used as a better alternative to dry or flood cooling method.

Antifriction Properties of Diamond-Like Coating and Titanium Aluminum Nitride in Model Lubricant Media

Abstract—The study investigates the antifriction properties of both a diamond-like coating (DLC) and titanium aluminum nitride (AlTiN) used as an intermediate layer to improve adhesion. Tribological tests of coatings were carried out without lubricant, in an inactive lubricant environment, and in lubricant environments with surfactant and chemically active additives. The studied DLC increases surface wear resistance and significantly lowers the friction coefficient; at the same time, the lubricant environment has no significant effect on the antifriction properties of the DLC.