Addition Of Solid Lubricants Research Articles

Effect of solid lubricant addition in coating produced by laser cladding process: A review

This present review article discusses about the effect of solid lubricant additive in surface composite coating deposited by laser cladding and alloying process. Wear and friction is challenging problem in moving machinery parts subjected to rubbing action or sliding motion. Therefore to reduce the wear and friction of sliding machinery parts, coated layer is deposited on the surface of machine component to prevent from surface damage due to wear. Laser cladding and alloying is advanced manufacturing technology by which hard and wear resistant coating material is deposited on the surface of soft conventional materials by use of high power laser energy as heat source to provide good metallurgical adherence between coating and substrate materials. The coating materials generally used for enhancing the friction and wear resistance properties of conventional materials are advanced ceramics, advanced composites, nanomaterials and advanced alloys like high entropy alloys. When solid lubricants are added to these coating materials in limited amount then the friction and wear properties of developed surface improves. The solid lubricant additive in coating materials can reduce the friction coefficient and wear rate of materials. The solid lubricant materials acts as anti-friction and anti-wear agent in the coating materials. The most commonly used solid lubricants are h-BN, CaF2, MoS2, WS2, BaF2 and graphite. In this article the effect of these solid lubricant material on wear resistance and friction coefficient of coated surfaces produced by laser alloying and cladding techniques are described. The various engineering materials used for manufacturing of moving or sliding parts are ferrous materials, titanium alloys, aluminium alloys, magnesium alloys and copper alloys. In this article the coating deposited on these materials with solid lubricant additives by laser cladding and alloying process are reviewed. The problem arises during developing solid lubricant additive coating and its remedies are described.

Compatibility of graphite, hBN and graphene with self-lubricating coatings and tool steel for high temperature aluminium forming

In recent years, the hot forming of aluminium has raised significant interest in industrial sectors such as the automobile and aerospace. However, such processes are not without difficulties, as the high adhesive wear characteristic of aluminium alloys is exacerbated at high temperatures and detrimentally affects the quality of the finished product. In an effort to improve this situation, different solid lubricant additives including hBN, graphite and graphene have been mixed with a commercial-grade lithium grease and evaluated under conditions representative of the high temperature forming of aluminium alloys, using an innovative single-pass, high temperature tribometer.Two different alloys have been chosen for the present study, including a nickel-based, self-lubricating laser cladding previously studied by the authors in the context of high temperature applications in addition to a reference tool steel widely used in metal forming industry. Experimental results showed a detrimental role of hBN as a solid lubricant, providing insufficient protection against adhesive wear and even leading to noticeable increases in the observed friction compared to other solid lubricants such as graphite. It has also been found that graphene excels at decreasing friction and material transfer from the aluminium counter body, suggesting a great potential as a lubricant additive in high temperature forming processes. However, the results of the present study indicate that graphene concentrations of 1 wt% are not enough for effective lubrication at high temperatures.

Moringa Oil With Pristine and Fluorinated Carbon Nanofibers as Additives for Lubrication

Abstract This study focuses on the influence of local moringa oil on the performances of lubricants obtained from a blend of dodecane and pristine or fluorinated carbon nanofibers at ambient temperature. The friction experiments have been evaluated using a reciprocating ball on a plane tribometer. Moringa oil is used as a bio-additive in lubricant formulations. First, the addition of a small amount of moringa oil to dodecane allowed a reduction of about 50% of the base oil friction performances. Second, a comparative study on the friction properties of their blends with pristine carbon nanofibers (CNFs) and fluorinated ones (CF0.85) was investigated, based on which they were intended to be used as solid lubricant additives. An adsorption effect of fatty acid molecules is observed in CNFs particles unlike CF0.85. Whatever was the percentage of moringa oil added, more promising results were obtained with CF0.85. Physicochemical characterizations of the tribofilms evidence the good antiwear properties of the lubricants.

Performance and mechanisms of different tribological thermoplastic composites in sliding contact with steel

Polyetheretherketone-based tribological materials are nowadays firmly established in a wide variety of technical applications. In parallel, numerous publications on the improvement of tribologically usable PEEK materials by means of different fillers have been presented from academic research. This paper shows, using five tribological PEEK compounds provided by industry as examples, a comparative evaluation in a wide pv range in sliding contact against steel. Using a special test technique, so-called load increase tests, characteristic parameters such as the coefficient of friction in the stationary friction phase and the integral wear are determined and the wear manifestations are investigated. Element analyses lead to the conclusion that, beyond the addition of carbon fibers and solid lubricants, the best tribological properties can be achieved by adding a wide variety of inorganic fillers.

Recent trends in laser cladding and alloying on magnesium alloys: A review

This paper discusses about the recent advancements in laser cladding and alloying processes used for surface property enhancement of magnesium and its alloys. Laser cladding and alloying is advanced manufacturing method used for surface modification of metallic materials in the modern industries. The cladding process is surface modification technique, which is used for deposition of thick layer of advanced materials on surface of conventional materials to improve the surface properties like, wear resistance, hardness, oxidation resistance, corrosion resistance, biocompatibility and heat resistance. The advanced materials generally used for cladding operations are transition metals, alloys, ceramics, composites, nanomaterials, rare earth oxide and some solid lubricant additives. The conventional substrate materials are steel, cast iron, titanium alloy, aluminium alloy, magnesium alloys and copper alloys. Laser cladding is most widely used coating technique because of its attractive properties such as low dilution rate, good metallurgical bonding between coating and substrate, less distortion, narrow heat affected zone, high solidification and cooling rate. In this article magnesium alloy is considered as substrate material and the various coating materials used for its surface modification are explained. Also, the effects of various laser process parameters on phase composition, microstructure, elemental composition, mechanical properties, tribological properties and corrosion resistance are discussed. The characterization techniques such as XRD, SEM, EDS, Vickers microhardness test, wear and friction test, corrosion test used for coating analysis are described. Furthermore, the problem arises in laser cladding and alloying on magnesium alloy and their possible remedies are discussed.

Mechanical property and cutting performance of (W,Ti)C based ceramic composites with the addition of nano-sized CaF2

In order to improve the mechanical property of self-lubricating ceramic cutting tool, (W,Ti)C based ceramic composites with the additions of nano-sized CaF2 solid lubricants were produced by vacuum hot pressing. Results showed that nano-sized CaF2 was mainly located in matrix grains and formed the intragranular self-lubricating nanostructure. The optimal mechanical properties were achieved at 1650 °C and 15 min. The flexural strength, hardness and fracture toughness reaches the maximum of 497 MPa, 16.3GPa and 6.48 MPa·m1/2, respectively. Compared with the ceramic composite without CaF2, the fracture toughness was increased by 13.0%. Dry machining tests of hardened 40Cr steel were performed with these ceramic cutting tools. It indicated that with the additions of nano-sized CaF2 as solid lubricant, the main cutting force and cutting temperature were reduced by 13.2% and 26.9%, the average friction coefficient of rake face was reduced from 0.59 to 0.32. SEM micrograph showed that a self-tribofilm was consistently formed on the rake wear area which has a good self-lubricating effect.

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.

Evaluation of mechanical and wear properties of aluminum 7075 alloy hybrid nanocomposites with the additions of SiC/Graphite

This research investigated the impact of graphite on Al 7075-SiC-Graphite hybrid composite's wear performance. The analysis demonstrates that effectiveness of graphite presence in the matrix to minimize wear. The hybrid metal matrix Nano composites were manufactured via Powder metallurgy process by reinforcing graphite at different weight fractions (0 percent, 5 percent) with 7075 aluminium alloy, the addition of Silicon Carbide (SiC) is fixed at 5 percent. The density, toughness, micro structural analysis, and wear performance of prepared hybrid nano composites have been analyzed and investigated. In the experimental investigation, it was observed that reinforcing particles are uniformly dispersed throughout the matrix alloy as perfect grain boundaries in alumnium solid solutions. The density and hardness of the reinforced composites have been significantly effected with the incorporation of the reinforcement when compared to a monolithic alloy. The significant increasing trend in mechanical properties and wear performance of aluminium hybrid composites was accomplished by the addition of solid lubricant (Gr) and strong ceramic reinforcing particles (SiC) in the matrix alloy.

Formation of Plasma Powder Coatings from Cermet with Subsequent High-Energy Modification

The paper presents research on the effect of technological parameters of high-energy processing on the performance properties of powder coatings made of cermet. The use of pulse-plasma treatment is considered as an example of high-energy modification of coatings. As used powder coating materials, various versions of carbide-containing ceramics with the addition of a solid lubricant in an iron-based metal matrix have been selected in the paper. Coatings of carbide-containing ceramics with the addition of a solid lubricant in an iron-based metal matrix on are being developed to replace those of a nickel-based matrix. Such factors as crack resistance, wear resistance, workability, brittleness, as well as economic components often limit the use of powder materials based on carbide ceramics with the addition of solid lubricant in the matrix based on nickel. When only the wear process determines the service life of a part, such powder materials should be replaced with cheaper powder materials based on carbide ceramics with the addition of solid lubricant in an iron-based matrix. The proposed developments increase the wear resistance of the plasma coating due to the introduction of high-chromium steel and molybdenum into the material. Optimum porosity is formed in the initial powder mixture during the synthesis of FeCrMo–MoS 2 –TiC composite materials, there is an improvement in the technological parameters of powder materials, their utilization rate in plasma spraying increases, and the technology of applying wear-resistant plasma coatings becomes cheaper. The addition of the Mo element to the FeCr binder increases the wetting of titanium carbides by the binder melt during self-propagating high-temperature synthesis of the developed composite powder. Subsequent layer-by-layer processing of plasma-sprayed coatings from powders of the developed ceramics using repetitive pulses of plasma flows using different energy levels makes it possible to create strictly defined structures with necessary and controlled porosity, which decreases in a certain sequence from the outer treated layers to the base. Such treatment contributes to a significant increase in the wear resistance of the treated friction surfaces, increases the oil holding capacity, in addition, an increased adhesive and cohesive strength of the formed layers bordering the substrate is formed. Processing distances, the total number of impacts have been varied in accordance with the methodological developments, when changing the applied technological characteristics of pulse-plasma effects. The total number of plasma pulses influences on the created thickness of the plasma coating layers after treatment and contributes to the melting with compaction of the coatings obtained by the plasma treatment and the creation of a structure with hardened characteristics.

Development of Al-Gr-Ca hybrid composite for braking application

This research deals with development of hybrid aluminium composite through traditional stir casting route. Varying weight percentage of alumina (8% & 12%) and constant weight of graphite (5%) are choosen to improve the basic and friction behaviour of aluminum .Pin on disc tribometer was utlized to under the wear behvaiour of developed composite at constant wear parameter viz constant load, velocity, and slding distance. The output showed that addition of reinforcement increase the hardness of fabricated composite. Likewise incremental percentage of alumina improvise the wear resistance of composite, this might be owing the addition of solid lubricants that forms tribo layer between the pin and contour disc parts.

High temperature tribological properties of YSZ/AgTaO3 sol-gel nanocomposite coatings

Composite coatings whereby soft and lubricious phases were embedded in a hard matrix displayed considerable enhancement in their mechanical and tribological properties that include frictional response, wear resistance, and material toughness. In the current study, composite coatings of a yttria-stabilized zirconia (YSZ) matrix embedded with different contents of AgTaO3 particles (0–30 wt%) were prepared by a sol-gel process and subsequently deposited on Inconel 718 substrates using the spin coating technique. X-ray diffraction (XRD) measurements indicated the presence of YSZ in the cubic phase and of AgTaO3. The tribological properties of the coatings were evaluated at 25 and 650 °C against an alumina (Al2O3) ball using a 2 N load. AgTaO3 was found to significantly enhance the coatings’ wear and friction properties especially at 650 °C. The addition of this high temperature solid lubricant was found to decrease the steady state friction coefficient from 0.65 to 0.18 and the wear rate from 7 × 10−5 mm3/nm to 6 × 10−6 mm3/nm for YSZ-30 wt%AgTaO3. Scanning electron microscopy (SEM) provided information about the surface topography and the elemental composition of the coatings before and after wear testing. SEM images suggested that an increase in AgTaO3 content resulted in the formation of a continuous film of this solid lubricant over an underlying YSZ-based coating. This continuous film provided better wear protection to the composite coating. These observations provide insights useful for developing composite coatings using the sol gel method and that display tunable tribological properties depending on the intended applications.

Silsesquioxanes-Based Nanolubricant Additives with High Thermal Stability, Superhydrophobicity, and Self-cleaning Properties

Nanoadditives are promising materials for long-envisioned next-generation lubricants to achieve excellent tribological performance and thermal stability. Here, an instigative and novel approach has been scrutinized to facilely prepare the nanolubricant additive. For this purpose, three synthetic strategies were designed for i) preparation of uniform-sized poly(methyl silsesquioxane) (PMSQ) nanoparticles, ii) hydrosilylation of the long carbon chain of ethyl 10-undecenoate and iii) modification of PMSQ nanoparticles with hydrosilylation product through a condensation reaction, in order to obtain long-carbon-chain grafted nanohybrids. The morphology, composition, and properties of these nanohybrids were confirmed by 1H-NMR, FTIR, SEM, EDS, and TGA. The effects of different concentrations of unmodified and modified PMSQ nanoparticles on the tribological properties of silicone oil were discussed. In the comparison of unmodified PMSQ nanoparticles, the modified one performs very well to reduce the coefficient of friction and wear scar diameter at low concentration. The TGA results revealed the extraordinary thermal stability of these particles, as their weight loss was only 19% at 800 °C which is remarkably higher than other solid lubricant additives. In this research, we tried to fill the deficiency of thermally stable material in the field of heavy machinery and industry. In addition, the environment-friendly (fluorine-free), superhydrophobic and self-cleaning surface effect of modified PMSQ nanoparticles was also observed. These silsesquioxane-based nanohybrids having synergistic effects, advantageous scientific values, and promising application prospects are expected to be more useful with other longer carbon chains.

Phase analysis and microstructure study of sintered Ni-Cr composites containing MoS2, Ag and CaF2 additives as solid lubricants

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 different temperatures (1000oC, 1100oC and 1200oC) under controlled atmosphere and various holding times. 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 Scanning Electron Microscope (SEM) and X-Ray Diffraction Analysis (XRD) while the hardness of the composites was measured by the Vickers Micro Hardness Tester. The results revealed that as the sintering temperature was increased, the sintered density, relative density and hardness also increased while the porosity was reduced. At the sintering temperature of 1200oC, the relative density reached its maximum value. SEM and XRD analysis confirmed the existence of MoS2 and Ag in sintered samples. MoS2 and Ag were not mainly dissolved and/or decomposed even after sintering at 1200oC

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.

Cover Image, Volume 69, Issue 5

AbstractThe cover image is based on the Research Article Graphite fluoride and fluorographene as a new class of solid lubricant additives for high‐performance polyamide 66 composites with excellent mechanical and tribological properties by Haoyang Sun et al., https://doi.org/10.1002/pi.5975. image

Influence of graphene/copper hybrid nanoparticle additives on tribological properties of solid cellulose lubricants

As solid lubricant additives, graphene and copper nanostructures improve the tribological behavior. In this study, hybrid nanoparticles are synthesized for application in HPMC lubricating films. The synthesis mechanisms of the various synthetic parameters (growth temperature, growth time, and methane flow) on the growth of graphene on nanocopper particles and the effect on the quality after parameter modulation are discussed. Furthermore, the tribological properties of graphene/copper hybrid particles and HPMC prepared into composite solid lubricating coatings are investigated. The addition of hybrid particles to the solid lubricant effectively reduces the friction coefficient by 35% and the wear volume by at least 50%. The addition of hybrid particle additives and the changes in the tribological mechanism are discussed in detail, in addition.

Graphite fluoride and fluorographene as a new class of solid lubricant additives for high‐performance polyamide 66 composites with excellent mechanical and tribological properties

AbstractFluorographene (FG) with layer numbers of 3–4 was successfully prepared through facile microwave‐assisted liquid phase exfoliation of raw graphite fluoride (GrF). The raw GrF and the as‐prepared FG were then directly incorporated into polyamide 66 (PA66) by melt processing without using any surfactants. Microstructural, mechanical and tribological properties of the prepared PA66 composites were investigated. Various characterization results showed that both GrF and FG, as novel solid lubricants, can effectively improve the mechanical and anti‐wear performances of the PA66 matrix. It was also found that FG is better at improving mechanical properties and reducing the friction of PA66 than GrF at low concentrations owing to the large surface–volume ratio. The addition of 0.5 wt% FG into PA66 exhibits a ca 13% increase in tensile modulus, ca 5% increase in tensile strength, ca 18% reduction in coefficient of friction (COF) and ca 43% reduction in wear rate. However, at relatively high concentrations, such as 1.0 wt%, GrF shows a better reinforcement effect than FG owing to a uniform dispersion of GrF in the PA66 matrix. The addition of 1.0 wt% GrF into PA66 exhibits a ca 18% increase in tensile modulus, ca 5% increase in tensile strength, ca 37% reduction in COF and ca 46% reduction in wear rate. Wear tests also show that the excellent wear resistance of the PA66 composites is due to the improved mechanical properties and the lubrication of GrF and FG between the worn surfaces. Our current work demonstrates the tremendous potentials of fluorinated carbon materials for enhancing mechanical and anti‐wear properties of polymeric materials. © 2020 Society of Chemical Industry

Effect of MoS2 on the Wear Behavior of Aluminium (AlMg0.5Si) Composite

Aluminium alloy with silicon as alloying element finds more comprehensive applications and this induces the development of aluminium composite with the matrix AA6063 (AlMg0.5Si) alloy. The applications of aluminium composites are majorly in the automotive, defence and aerospace industries, where the parts subject to relative motion. Wear and friction are significant issues, and the effective method to overcome is the replacement of newer materials with self-lubrication properties. An attempt is made to develop one such self-lubricating composite material with aluminium matrix is made with the addition of solid lubricant molybdenum disulfide. The present study focus on the investigation of wear performance of the developed self-lubricating composite through the dry sliding wear analysis. The addition of solid lubricant enhanced the wear resistance even at the initial stage of the run and resulted in a steady state of wear from 200 m sliding distance. Also, the wear mechanisms which influence the wear performance were detected through the microstructural examination, and it was discussed.

Study on the effectiveness of WS2 and CaF2 on the performances of self-lubricating micro impregnated diamond bits

Self-lubricating micro impregnated diamond bits (IDBs) were manufactured for the first time via hot-pressing powder metallurgy to investigate the effectiveness of two promising solid lubricant additives, WS2 and CaF2, in improving IDBs' self-lubricating and drilling performances through laboratory drilling test and micro analyses. It was found that, with increase in lubricant concentration, the rate of penetration (ROP) of WS2 IDBs increased exponentially, while that of the CaF2 IDBs decreased monotonically from its maximum value at 6 vol% CaF2 concentration. For WS2 IDBs, the increase in ROP was at the sacrifice of substantial deterioration of IDBs' service life, while the service life of CaF2 IDBs gradually increased to surpass that of lubricant-free IDBs at 8 vol% CaF2 addition and continued to grow. Micro analyses, including measurement of diamond protrusion height and micro morphological analysis of IDBs' worn surface, were conducted using a confocal laser scanning microscopy (CLSM). The 10 vol% CaF2 IDBs were found under good protection from either matrix or diamond wear. By contrast, the surface of the 6 vol% WS2 IDBs suffered severe wear. Based on CLSM images, it was inferred that the high ROP and low service life of WS2 IDBs were a result of enhanced three-body abrasive wear by breakaway diamond grits. In general, self-lubricating IDBs with 10 vol% CaF2 addition acquired best overall performances in that they achieved longest service life while having higher ROP than lubricant-free IDBs.

Addition of molybdenum disulfide solid lubricant to WC-12Ni thermal spray cemented carbide powders through electroless Ni-MoS2 co-deposition

Molybdenum disulfide solid lubricant was added to thermal spray WC-12Ni powders through electroless Ni-MoS2 co-deposition. With varying the concentration of WC-12Ni and MoS2 particles in the plating bath, varied concentration of MoS2 can be controlled in the powder surface layer and the incorporation mechanism of MoS2 into the shell was discussed as well. The thickness of the Ni-MoS2 coatings as well as the MoS2 distribution structure were characterized with a scanning electron microscope (SEM) equipped with an energy dispersive spectrometer (EDS). The phase structure of the co-deposited coatings was characterized with X-ray diffraction (XRD). It is found that MoS2 particles can be co-deposited with Ni to form a Ni-MoS2 composite layer on WC-12Ni powders when effective Ni electroless deposition occurs, since Ni or Ni2+ can encapsulate MoS2 particles to facilitate its incorporation. The content of MoS2 in the coating increases with increasing the concentration of MoS2 in the plating bath, or with decreasing the concentration of WC-12Ni powders in the bath which results in increased thickness of deposited Ni- MoS2 layers. The Ni-MoS2 coated WC-12Ni powders obtained with the electroless co-deposition process can be used for high velocity oxy-fuel spraying (HVOF) with a proper size and adequate fluidity, and are expected to suppress desulfurization and decarburization effectively.