MoS2 Solid Lubricant Research Articles

Surface integrity in drilling AA5052 + 3 %MoS2 + 9 %Si3N4 HAMMC and comparing the results with AA5052 + 9 %Si3N4 AMMC - experimental studies and optimization

The purpose of this study is to compare the surface roughness (SR) achieved during drilling the fabricated aluminium metal matrix composite (AMMC) considering AA5052 as base matrix and 9 % silicon nitride (Si3N4) ceramic as reinforcing phase with hybrid aluminium metal matrix composite (HAMMC) added with 3 % of solid lubricant MoS2 (AA5052 + 3 %MoS2 + 9 %Si3N4) using carbide drill bit. The novel AMMC and HAMMC are fabricated by the traditional liquid casting technique. For investigation of the drilling process two groups were selected: an experimental group (AA5052 + 3 %MoS2 + 9 %Si3N4) and control group (AA5052 + 9 %Si3N4). Based on the sample size calculator, 20 samples were considered for each group for performance comparison. A CNC vertical machining center was adopted for performing the drilling process with a carbide drill bit without the application of coolant which is termed as green machining. From the outcomes of this research work it is identified that with the inclusion of solid lubricant MoS2, surface roughness is reduced because of friction reduction among workpiece and drill bit. The mean value of SR for the experimental group is 0.806 μm whereas for the control group it is 1.281 μm. During statistical analysis with Independent sample T-test, significance obtained is 0.008 which is below the ideal value of p < 0.05. Hence a significant variance exists among the considered groups. Within the limit of this study it is identified that AA5052 + 3 %MoS2 + 9 %Si3N4 developed superior surface finish during the machining process because of the inclusion of solid lubricant MoS2 against the fabricated AMMC.

Structure and Tribo-Mechanical Properties of MoSx:N:Mo Thin Films Synthesized by Reactive dcMS/HiPIMS

Modifying MoS2 thin films by additional elements shows great potential in order to adjust the property profile and to meet the increasing requirements regarding high wear resistance and low friction properties of industrial components. Within that context, MoSx:N:Mo thin films were deposited by a reactive hybrid dcMS/HiPIMS process. By systematically increasing the Mo target cathode power, an investigation of the structural and the mechanical properties was conducted to understand the evolution of the tribological behavior. A low Mo target cathode power of 1 kW is related to the formation of the preferential (002) MoS2 basal-plane and thus a low friction with µ = 0.2. With an increasing amount of Mo, the film loses its solid lubricant MoS2 properties and a nitride constitution of the thin film is developing due to the formation of crystalline Mo and MoN phases. Related to this transformation, the hardness and elastic modulus are increased, but the adhesion and the tribological properties are impaired. The film loses its plasticity and the generated film material is directly removed from the contact area during the sliding contact.

Wear behavior of A356/ Al2O3/MoS2 hybrid nanocomposites

A356 composites with alumina and molybdenum disulfide nanoparticles are a distinct category of engineered materials developed for tribological use. This evolution has led to an attempt to investigate the microstructure and wear behavior of A356 hybrid nanocomposites reinforced with nano Al2O3 (0.5, 1, and 1.5 wt% of Al2O3) and nano MoS2 (0.5 wt% of MoS2) is fabricated by stir casting technique. Wear behavior of A356/ Al2O3/ MoS2 nanocomposites was tested by using the pin on disc equipment. The sliding wear tests were carried out at 10–50 N normal load insteps of 10 N, 2 m/s sliding velocity and 1000–5000 m sliding distance insteps of 1000 m/s. Results have shown that the increase of alumina and the addition of MoS2 nano particles have a positive impact on the improvement of tribological properties of the hybrid nanocomposites. The coefficient of friction and wear rate of hybrid nanocomposites are reduced with the addition of Al2O3 and a solid lubricant MoS2 particle.

Fabrication and Modelling of Tribological Performance of Al-Si/12Al2O3/2MoS2 Composite using Taguchi Technique

This paper investigates the effect of mechanical, microstructural and dry sliding wear behaviour of Al-Si/2wt%MoS2, Al-Si/12wt%Al2O3, and Al-Si/12wt% Al2O3/2wt%MoS2 composites that prepared using the stir-casting route. To avoid friction and wear at the interfaces of materials, an attempt has been made by adding solid lubricant MoS2 to build such a self-lubricating composite with Al-matrix. The tribological analysis has been described based on the Taguchi orthogonal array (L27). Three variables combination such as sliding velocity, sliding distance and contact pressure are used for this study to determine the tribological responses, i.e. wear rate and coefficient of friction. The properties of composites were improved by increasing the weight % of MoS2 and Al2O3. The tensile strength of Al-Si/2MoS2, Al-Si/12Al2O3, and Al-Si/12 Al2O3/2MoS2 composites is 6.02%, 12.46%, and 2.44% compared to the base matrix. The addition of MoS2 helps the hybrid composite to attain better tribological properties with a slightly lower specific strength. Analysis of variance showed that the composites such as Al-Si/2 MoS2 and Al-Si/12Al2O3/2MoS2 were strongly influenced by the pressure in wear rate. Similarly, sliding velocity affects the coefficient of friction for Al-Si/2MoS2. Wear tracks formed during the dry slide process were analysed using optical and SEM with an EDS. It was discovered that pressure plays a vital effect in the wear mechanism. The hybrid composite (Al-Si/12 Al2O3/2MoS2) material can be utilised in place of conventional materials in tribological demanding automotive applications

Impact of MoS2 solid lubricant on surface integrity of Ti-6Al-4V with PVD-TiN coated tool in drilling

Impact of MoS2 solid lubricant on surface integrity of Ti-6Al-4V with PVD-TiN coated tool in drilling

Improvement of thread turning process using micro-hole textured solid-lubricant embedded tools

In this paper, the thread turning of aluminum 7075-T6 alloy is studied using micro-hole textured solid-lubricant embedded carbide inserts. The primary focus of this work is to enhance the performance of the thread turning process for producing high quality threaded parts. To achieve this, micro-holes were generated by laser micro-machining on the rake face of tools and then, MoS2 and CNT (carbon nanotube) solid-lubricants were embedded into micro-holes. The effects of micro-holes and solid-lubrication on the performance of the thread turning process were examined using traditional tool ( T0), micro-hole textured tool ( T1), micro-hole textured MoS2 embedded tool ( T2), and micro-hole textured CNT embedded tool ( T3). In this study, cutting forces, chip-tool contact length, built-up edge (BUE), surface roughness, and operating cost were investigated. The influence of micro-hole generation on the mechanical strength of cutting inserts was evaluated using the finite element method. The results showed that the fabrication of the micro-holes on the rake surface of cutting inserts has no significant effect on the mechanical strength of the tools. The comparisons of our method with traditional tools demonstrated that the cutting performance improved in the threading process. Our results reveal that the main cutting force, radial thrust force, surface roughness, built-up edge, and chip-tool contact length reduced 37.1%, 40.9%, 37.9%, 58.3%, and 38.2%, respectively, as T3 tools are applied in this process. A cost analysis, based on estimated tooling costs, showed that the T3 tool can yield an 18% reduction in overall operating cost.

Microstructure, Mechanical Properties and Tribological Behavior of Magnetron-Sputtered MoS2 Solid Lubricant Coatings Deposited under Industrial Conditions

Depositing MoS2 coatings for industrial applications involves rotating the samples during the PVD magnetron sputtering process. Here, we show that a 3-fold substrate rotation, along a large target–substrate distance given by the deposition unit, introduces porosity inside the coatings. The mechanical properties and wear behavior strongly correlate with the degree of porosity, which, in turn, depends on the temperature and the rotational speed of the substrate. Ball-on-disk tests and nanoindentation wear experiments show a consistent change in tribological behavior; first, a compaction of the porous structure dominates, followed by wear of the compacted material. Compaction was the main contributor to the volume loss during the running-in process. Compared to a dense coating produced without substrate rotation, the initially porous coatings showed lower hardness and a distinct running-in behavior. Tribological lifetime experiments showed good lubrication performance after compaction.

Comparison of dry sliding tribological behavior of SS 316L impregnated with MoS2 vs h-BN solid lubricants: A statistical point of view

The main aim of this paper is to statistically discuss the friction and wear behavior of 316L stainless steel (SS316L) composites added with h-BN and MoS2 solid lubricant under different running conditions at room temperature. The SS316L composites added with h-BN and MoS2 were produced by the powder metallurgy method. The mixture of SS316L composites with 15 and 20 vol% of h-BN and MoS2 were cold compacted into ∅ 30 mm cylinder parts. Then sintered in the sintering furnace under H2 atmosphere for 60 min. Brinell's hardness and dry-sliding wear behavior of the sintered SS316L composites were investigated using a pin-on-disc testing machine. The factorial experimental design was employed to investigate the influence of specific independent variables on dry sliding wear, testing at sliding speeds of 0.1 and 0.2 m/s, applied load of 3 and 5 N and sliding distance varying from 100 to 200 m. The effects of tested variables on the specific wear rate and coefficient of friction were analyzed from both statistic plots and physical analyses of worn surface with SEM micrographs. The results showed that the MoS2 added composite resulted in greater wear resistance than h-BN added composite. The wear resistance and friction coefficient on dry sliding wear test also depended on the interaction effect of sliding distance, sliding speed and applied load which are relative to the formation of tribofilm on sliding interfaces. In addition, sliding speed influence to the formation of tribofilm showed significantly high levels of wear resistance and friction coefficient of composites. The statistical design of this experiment enabled us to collect and analyze wear data which provided a greater understanding of the complex mode/mechanism of sliding wear of SS316L self-lubricating composites.

Slippery polymer monoliths: Surface functionalization with ordered MoS2 microparticle arrays

Components of technical systems and devices often require self-lubricating properties, which are implemented by means of dry lubricants. However, continuous lubricant coatings on the components’ surfaces often suffer from poor adhesion, delamination and crack propagation. The replacement of continuous coatings with dense ordered arrays of microparticles consisting of dry lubricants may overcome these drawbacks. Using the well-established solid lubricant MoS2 as model system, we demonstrate that the sliding capability of polymeric monoliths can be significantly enhanced by integration of arrays of micron-sized dry lubricant microparticles into their contact surfaces. To synthesize the MoS2 microparticle arrays, we first prepared ordered hexagonal arrays of ammonium tetrathiomolybdate (ATM) microparticles on Si wafers by molding against poly(dimethylsiloxane) templates followed by high-temperature conversion of the ATM microparticles into MoS2 microparticles under Ar/H2 atmosphere in the presence of elemental sulfur. Finally, the obtained large-scale hexagonal MoS2 microparticle arrays were transferred to the surfaces of polymer monoliths under conservation of the array ordering. Self-lubrication of components of technical systems by incorporation of dry lubricant microparticle arrays into their contact surfaces is an example for overcoming the drawbacks of continuous functional coatings by replacing them with microparticle arrays.

Sliding Friction Behavior of Sintered Ni-Cr Composites with Solid Lubricants

High temperature applications of self-lubricated sliding surfaces have gained industrial importance during the recent years. One popular system is based on sintered Ni-Cr composites with addition of solid lubricants. In the present work these composites were prepared under controlled sintering conditions with different combinations of solid lubricants (MoS2, Ag and CaF2) at 1200 °C under flowing argon. The physical properties such as sintered density, relative density and porosity were studied. The microstructures and phase studies of the Ni-Cr based composites were conducted using SEM analysis while the hardness of the composites was measured by Vickers Micro Hardness Tester. The friction tests were conducted with ball on disc configuration following ASTM G-99-95a standard. The MoS2 solid lubricant provides best lubrication at room temperature which is demonstrated by a low friction coefficient compared to pure Ni-Cr composites. The SEM pictures of worn out tracks show solid debris distribution, and filling of pores with solid lubricant phases. The time taken for stabilization of friction coefficient also varies with the type of solid lubricant. Dual and multiple additions of solid lubricants are also able to reduce the friction of coefficient compared to pure Ni-Cr composite.

Optimization of Pulsed Fiber Laser Texturing for Solid Lubricant Deposition on a Ti/TiN Coated Aerospace Alloy

AA2219 is a superior performance Al-base alloy which promises toughness, strength and creep resistance which allows the deposition of titanium nitride (TiN) coating at 200 °C. The present research addresses the issue of poor wear properties of the alloy, using state of the art technologies, to deposit hard and adherent thin TiN layer followed by laser surface texturing. The thickness of sub-micron size coating is determined by appropriate modification of the existing mathematical model and composite microhardness values. Laser energy density of 20.8 J/cm2 and 4 repeated pulses is optimized to produce regular size and shape of micro-holes on TiN-coated samples. Epoxy-based MoS2 lubricant is deposited on laser textured samples to produce ultra-low friction surfaces. The micro-holes act as a micro-reservoir of MoS2 solid lubricant. Field emission scanning electron microscope and optical profilometer were used to estimate the topology, shape, size, and depth of micro-holes. The cross-sectional view shows the successful impregnation of epoxy-based MoS2 due to the chemisorption of functional groups with an Al oxide surface.

Machinability study of Ti-6Al-4V alloy using solid lubricant

Cutting tool suffers rapidly during machining titanium-based alloys due to low thermal conductivity. Thus most of the heat is concentrated on the tool rather than chip during machining. To overcome this problem, a suitable cutting parameter, tool geometry, and sustainable methods are necessary. This paper presents the effect of MoS2 solid lubricant (SL), cutting speed, and nose radius during turning of Ti-6Al-4V alloy using the TiAlN coated carbide tool. The experiments are performed at different cutting speeds, nose radius, and flow rates of solid lubricant to study tool wear, surface roughness, and chip morphology. The results show that the use of solid lubricant reduces the tool wear (37%), and the surface roughness (65%) compared to the dry cutting. Similarly, the effects of nose radius and cutting speed have also been studied for both conditions.

Tribological properties of MoS2 coating for ultra-long wear-life and low coefficient of friction combined with additive g-C3N4 in air

The solid lubricant MoS2 demonstrates excellent lubricating properties, but it spontaneously oxidizes and absorbs moisture in air, and thus results in poor wear resistance and short wear-life. In this study, the additive g-C3N4 (CN) was successfully combined with MoS2 via hydrothermal synthesis as a solid lubricant for the first time. Meanwhile, a low friction coefficient (COF, μ = 0.031) and ultra-long wear-life of CN/MoS2 compared to pure MoS2 in air were demonstrated. The functional groups and good crystallinity of the lubricant material were characterized via Fourier transform infrared (FTIR) spectroscopy and X-ray diffraction (XRD). The formed valence states in CN/MoS2 were analyzed via X-ray photoelectron spectroscopy (XPS). The characterized results of the scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HRTEM) show the morphology and interior crystal phase structure of CN/MoS2. From the cross-section analysis, the presence of iron oxide nanoparticles lubricating film is synergistic with CN/MoS2 film during the friction process, resulting in its ultra-long wear-life. In particular, the friction mechanism of interlayer sliding friction combined with energy storage friction was analyzed and proposed.

Microstructure and surface characterization of Ni-Cr based composites containing variable solid lubricants

ABSTRACT Ni-Cr based composites with and without the addition of solid lubricants (MoS2, Ag and CaF2) were prepared by powder metallurgy method. The samples were sintered at 1200°C in flowing argon atmosphere for 1 h. The physical properties such as sintered density, relative density and porosity were studied. The microstructures and phase studies of the Ni-Cr based composites were conducted using SEM analysis while the hardness of the composites were measured by Vickers Micro Hardness Tester. The friction tests were conducted with ball on disc configuration following ASTM G-99-95a standard. The MoS2 solid lubricant provides best lubrication at room temperature which is demonstrated by a low friction coefficient compared to pure Ni-Cr composites (0.176 compared to 0.394). The SEM pictures of worn out showed into evidence plastic deformation, solid debris distribution, and filling of pores with solid lubricant phases. The time taken for stabilization of friction coefficient also varies with the type of solid lubricant. Dual and multiple addition of solid lubricants are also able to reduce the friction of coefficient compared to pure Ni-Cr composite. SEM analysis shows the spreading of solid lubricant/s during the sliding test to provide lubrication to both contacting metals.

Effect of Humidity on Friction of Molybdenum Disulfide Films Produced by Thermal Evaporation on Titanium Substrates

MoS2 is one of the most advanced solid lubricants that have been used in many machineries. In this work, the effect of humidity on the friction of MoS2 solid film lubricant is investigated using a pin-on-disk tribometer. MoS2 film was coated by a thermal evaporation method on a titanium substrate. Steel and aluminum pins were used for the evaluation of friction coefficient of MoS2 films using a tribometer. The tests showed that with an increase in humidity, the coefficient of friction also increased. In practical applications at high humidity levels, the MoS2 films could be covered by condensed water molecules. Therefore, an experiment to understand the effect of water film on the variation of friction coefficient was also conducted. The results showed that the coefficient of friction remained constant for experiments using both aluminum and steel pins, and then the coefficient of friction increased once the water film was evaporated by the heat generated due to friction. An optical and XRD characterization of the MoS2 film was also conducted.

MoS2 solid lubricant application in turning of AISI D6 hardened steel with PCBN tools

This research investigates the effect of the application of MoS2 mixed with oil in the hard turning of AISI D6 cold work tool steel with PCBN tools. A 33 statistical factorial planning was used to run the tests, variables: cutting speed, feed rate; lubri-cooling conditions: dry cutting, pure oil applied by MQF (minimum quantity of fluid), oil mixed with solid lubricant (MoS2) applied by MQF. The main tool wear mechanisms were abrasion, attrition (or adhesion), and diffusion. The EDS of the PCBN confirmed the presence of MoS2, indicating that solid lubricant particles took place in the lubrication process at the cutting region. The results suggest that use of solid lubricant in hard turning may be a viable alternative to tackling the challenge of machining difficult-to-cut materials.

Enhancement of metallic machine parts mechanical properties by the use of vibratory processing for oxide coated films formation and MoS2 solid lubricant coating deposit

Experimental studies have been carried out to establish the possibility of using vibratory machining technology through shock-wave transmission for oxide coating preparation on aluminum-alloyed machine components and also to discuss the technological possibilities of applying vibration mechanochemical solid lubricant coatings based on MoS2 to improve the surface quality and performance properties of machine component parts. The coating characteristics are determined by measuring and comparing certain tribological properties of the samples before processing, after normal coating, and after vibratory coating process. A deeper study with a scanning microscope was made by comparing result of normal and vibratory coating. The vibratory coating shows a reduction of grain sizes, a regular orientation of the grain, and a dense grain structure leading to the formation of a thin layer covered by a film orientated parallel to the surface of friction giving an imparted surface finish. The reduction of microroughness is also accompanied with good performances in terms of increasing in wear resistance and decreasing in coefficient of friction. This reflects the presence of complex influence of mechanical and chemical components in the formation of coating on superficial layers during lower shock-wave vibration giving at the end structured ameliorated state of surface that leads to an increase in the part lifespan and equally shows technological opportunities that can be used to improve surface quality and performance properties of machine component parts.

The Functional Properties Acquired by Antifriction Composites Produced from Silumin Grinding Waste

The paper analyzes how the antifriction composites produced from AK12MMgN silumin grinding waste with MoS2 solid lubricant additions acquire their structure and porosity. The materials are intended to perform in friction joints at elevated loads of 2.0–4.0 MPa and sliding velocities of 1.0−3.0 m/s in air. It is shown how the process developed for producing these materials influences their structure and tribotechnical properties. The distribution of MoS2 in the AK12MMgN-matrix composite, its role in the self-lubrication mechanism, and the distribution of MoS2 and chemical elements of the friction joint in the contact zone in the sliding friction conditions corresponding to actual operation of joints in a printing machine are studied. The solid lubricant is uniformly distributed over the friction surfaces and thus covers the entire friction zone in the friction process. The tribological films formed in the presence of a MoS2 solid lubricant promote high antifriction properties of the composite produced from silumin waste. These properties allow the operational conditions to be improved and extend the application of new wear-resistant materials produced from recycled materials in contact joints of printing machines.

Tribological and mechanical properties of MoS2 enhanced polyamide 12 for selective laser sintering

The solid lubricant MoS2 was used as the reinforcement filler for the Polyamide12 material for the additive manufacturing process – selective laser sintering. The tribological and mechanical properties of the laser sintered PA12/MoS2 and PA12 were investigated by the linear reciprocating ball-on-flat wear and impact tests. Results show that by incorporating the MoS2 filler into the PA12 matrix, the impact properties was improved. The coefficient of friction and wear rate of the laser sintered PA12/MoS2 were reduced significantly. The worn surface formed in the wear test was shallow and smoother for the PA12/MoS2, where only mild wear occurred. The XPS testing suggested the involvement of the mechanical-chemical reaction, which resulted the decomposing of the MoS2 and the enhancement of the wear properties of the PA12/MoS2.

Surface Engineering Design of Alumina/Molybdenum Fibrous Monolithic Ceramic to Achieve Excellent Lubrication in a High Vacuum Environment

Al2O3/Mo fibrous monolithic ceramics are potential candidates for space applications because of their excellent mechanical properties and low density. This study aims at achieving low friction and long life of this material in a high vacuum environment. Three-dimensional composite-lubricating layers were fabricated by considering texture pattern as storage dimples and MoS2 synthesized via hydrothermal method as lubricant. The tribological properties were studied sliding against Si3N4 ceramic and GCr15 bearing steel balls under high vacuum condition. Results showed that the lubricating properties of the Al2O3/Mo fibrous monolithic ceramics were improved greatly by the micro-texture and MoS2 solid lubricant; the friction coefficients were as low as approximately 0.08 and 0.04, respectively, when Si3N4 ceramic and GCr15 bearing steel balls acted as the pairing materials. It was also demonstrated that the low friction coefficient can be realized with various normal loads and sliding speeds, indicating the composite-lubricating layers have good adaptation of working conditions. This excellent performance of the material is mainly because of MoS2 stored in dimples can be easily dragged onto the friction surface to form lubricating and transferring films during the friction process. This work is an extension of studies that were previously published in Tribology Letters journal.