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The paper reports on the comparative potential of nano-particles and micro-particles of mica in glass fiber reinforced Polyaryletherketone (PAEK) composite containing graphite (10 wt%). Very high PVlimit value (>100 MPa-m/s), very low specific wear rate (K0) (2–∼8 × 10−16 m3/Nm) along with very low friction coefficient (μ) (0.04–0.08), were exhibited by the composites. The PVlimit values of a nano-composite (NC) and micro-composite were 126 and 84 MPa m/s respectively. Friction and wear performance of a nono-composite was significantly better at lower PV conditions (40% lower in wear rate and 20% in friction). Worn surfaces were studied by scanning electron microscopy (SEM) and 3D profilometer, while the interaction of the constituents with a disc surface was investigated with the X-ray photoelectron spectroscopy (XPS).

Hexagonal boron nitride (hBN), also called as white graphite is known to exhibit excellent combination of thermal, thermo-physical, mechanical and tribological properties as a filler (solid lubricant). Not much reported on its potential as nano-particles. In this study, micro and nanocomposites of hBN were prepared with the combination of polyaryl ether ketone (PAEK) as a matrix (50%), short glass fibers (GF) (30%) as a reinforcement and natural graphite (10%) as a primary solid lubricant (SL) apart from hBN particles (10%) as a secondary SL. The micro-composite (MC) and nano-composite (NC) contained hBN particles in micron size and combination of micron and nano size (7 and 3%) respectively. The NC exhibited enhanced mechanical and tribological performance compared to the MC. Tribological tests were performed on a pin-on-disc tribometer under dry sliding regime to evaluate PVlimit (pressure x velocity) values. Influence of load and sliding speed on the friction coefficient (μ) and specific wear rate (K0) on the composites was investigated. The composites showed PVlimit of 100 MPa m/s along with μ in the range of 0.04–0.08 and K0 in the range of 2.5–7 × 10− 16 m 3/Nm. It was also found that the superior performance of NC was due to more efficient, thin and coherent film transferred on the disc. Moreover, structural and morphological changes were studied with Raman spectroscopy and scanning electron microscopy (SEM). Wear mechanism of the worn surfaces were discussed using XPS (X-ray photoelectron spectroscopy).

Wear corrosion is a significant problem impacting the lifetime of steel pipes used in hydraulic fracturing operations. To improve the lifetime of these steel pipes, the present work examines the effect and optimization of three propriety corrosion inhibitors (Dynarate, DWP, and CalGuard), as well as their concentration, on the tribocorrosion behavior of AISI 4715 steels used to carry fracking liquid from their storage pool to the geological formation. The wear and corrosion behavior of AISI 4715 steel was investigated using a reciprocating tribometer integrated with a three-probe electrochemical apparatus. Response surface methodology (RSM) was applied to statistically model the effects of various concentrations of Dynarate, DWP, and CalGuard, along with their combinations, on the average coefficient of friction (COF), as well as the total wear loss of the steel and optimize them. The overall results revealed that Dynarate significantly decreased the COF (0.147) and wear rate (0.3 mm/year) with an inhibition efficiency of 480% at a concentration of 1%. To investigate the effectiveness of the regression model at predicting the wear rate, the samples were characterized using 3D optical profilometer and scanning probe microscopy to describe the effect of various additive on the surface morphology of steel. The surface topography measurements indicated the worn regions for the samples where the Dynarate additive was used were smoother compared with those having the DWP and CalGuard additives.

In this work, the influence of amount (30 and 40 wt.%) of short glass fibers (SGF) in two composites containing synthetic graphite (10 wt.%) and Polyaryl ether ketone (PAEK) (60 wt.% and 50 wt.%) on thermal, mechanical and tribological performance was studied. The theme was to investigate wear-mechanical property correlation. Although the higher amount of SGF led to higher mechanical properties, tribological properties were not in tune to this. Overall, friction coefficient (µ) and specific wear rate (K0) for the composites were in the range 0.04–0.08 and 3–8 × 10−16 m3/Nm respectively and decreased with increase in applied PV values till failure was observed. PVlimit was indicated at 112 and 100 MPa m/s for 30 wt.% and 40 wt.% SGF filled composites respectively. The mechanical properties of the composite with 40 wt.% GF (CGF40) proved superior to a composite with 30 wt.% GF (CGF30).

While designing the ambitious advanced composites based on PAEK (50 wt%), glass fibers (30 wt %) and natural graphite (10 wt %), it was proposed to include one more solid lubricant (10 wt %) from the category of metal chalcogenides. Particles of MoS2 and WS2 in micron and nano-sizes were selected for inclusion in combination with natural graphite. The themes for investigations were; which one is the better performer amongst MoS2 and WS2, and nano-particles can impart beneficial effect or not; and the last how efficient would be these tribo-composites in terms of friction, wear resistance and PVlimit values. The composites were characterized in detail for physical, mechanical, thermal and tribological performance. The WS2 proved more beneficial till moderate PV conditions but not for severe conditions as compared to MoS2. The composites proved excellent tribo-materials in terms of low friction (∼0.04), wear rate (2.2 × 10−16 MPa m/s) and PVsafe values (84 MPa m/s). The chemistry of the counterface surface was studied using X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy (RS) while the morphology of the worn pins surface and counterface surface was observed using a combination of 3D profilometer and scanning electron microscopy.

In this study, we examined the wear-corrosion rate of AISI-4715 pipe sections using a three-probe electrochemical controlled reciprocating tribometer. The impact of additive chemistry on the friction coefficient, as well as their associated impact on the wear rate was determined. A significant increase in the wear rate (10-times) was observed in hydraulic fracturing fluid with high total disolved solids (HTDS) compared with distilled water. Due to the boundary lubricant nature, mixing of two different organic corrosion inhibitors with HTDS water showed a significant decrease in the friction and wear response (2–3 fold). Finally, the addition of corrosion inhibitor also impacted synergistically to improve the wear-corrosion resistance. Corrosion mitigating efficacy of different inhibitor combinations were correlated well with theoretical corrosion kinetics.

Poly aryl ether ketone (PAEK) is known as a high performance polymer superior to PEEK (poly ether ether ketone) in many aspects such as temperature stability, tribo-performance etc. Recently few efforts are put to enhance the tribo-potential of PAEK by developing composites containing short fibers of carbon and glass and most favored lubricants such as graphite, PTFE (poly tetrafluoroethylene), hexa boron nitride (hBN) etc. The wear and friction got significantly reduced to the extent that the composites showed very high potential as bearing materials for harsh operating conditions. Mica and boric acid (BA) are known as very good solid lubricants (SLs) with layer lattice structures. Potassium titanate (KT) powder also has been very popular ingredient of friction materials responsible for increasing wear resistance (W R ) and reducing friction fluctuations. It is, however, never explored in bearing materials for enhancing tribo-potential. Keeping this in view, a series of composites was prepared by injection molding with identical parent composition but differing in type of solid lubricants (hBN, KT, BA and Mica). The tribo-performance was evaluated in adhesive wear mode on tribometer under severe operating conditions (700–900 N, velocity 1.63–3.5 m/s). Composites exhibited very low specific wear rates (K 0 ) (2–8×10 –16 m 3 /Nm) and very low coefficient of friction (µ) (0.04–0.08), which decreased with load and velocity. KT proved to be the most performing filler, while Mica was least effective followed by BA. Worn surface analysis by SEM (Scanning electron microscopy) and EDAX (energy dispersive x-ray) helped to understand wear mechanisms.

In the present study, tribo-potential of a combination of two solid lubricants (SLs) viz. a special graphite i.e. thermographite (TG) and hexa boron nitride (hBN) in a series of composites with fixed amount of short glass fibers (GF 30 wt %) and Polyaryletherketone (PAEK- 50 wt%) was investigated under severe operating condition (Load 900 N (Pressure-28 MPa), speed >1.6 m/s) against mild steel disc till the composites failed. All the composites showed excellent performance under very high PV (pressure and velocity) values and the performance depended mainly on operating parameters and amount of two SLs in the composites. It was observed that 20% of a single SL (either TG or hBN) did not show very good results, although TG inclusion proved better than hBN. When these two SLs (20%) were used in combination, synergistic effect was observed and best performance was exhibited by a composite containing 5% hBN and 15% TG with the highest PV limits of 102.2 MPa m/s (900 N, 3.65 m/s) along with very low μ (0.04) and specific wear rate (5.68 × 10−16 m3/Nm), followed by composite with 10% TG and 10% hBN. Combination of 15% hBN and 5% TG stood next in performance. Synergism in tribo-performance due to combination of two SLs was reported for oils and friction materials but not for high performance anti-friction materials. Such composites have excellent potential as materials for dry bearings, gears etc. The Scanning electron microscopy (SEM) and Energy Dispersive X-ray analysis (EDAX) studies on worn surfaces proved beneficial to understand how the fiber-matrix bonding was affected due to different combinations of SLs and how it affected wear performance.

A novel type of graphite (thermographite) having higher thermal conductivity (TC) due to a patented treatment is commercialized recently. It was anticipated that such particles would be more effective in conducting away frictional heat generated on the tribo-surfaces leading to the enhanced performance. Hence two composites were developed based on high performance Polyarylether ketone (PAEK) (50% by wt) containing 30% short glass fibers (GF) and hexa-boron nitride (hBN) 10% apart from 10% graphite. First composite designated as CNG contained 10% natural graphite (NG) while the other designated as CTG contained 10% thermographite (TG). These were processed by identical method (twin screw extrusion followed by injection molding). The tribo-performance was evaluated in a pin on disc (mild steel) configuration under very high load and speeds. It was observed that both the composites exhibited excellent tribo-performance. However, CNG performed better than the CTG in all respects only under severe operating conditions. Under low PV conditions, difference was not clear. It showed lower friction coefficient, and wear rate as compared to CTG. CNG showed PVlimit value 96.6 MPa-m/s which was decisively superior to CTG (91 MPa-m/s). CNG could sustain higher speed (3.45 m/s) than the CTG (3.25 m/s) under 900 N in spite of slightly lower TC. It was concluded that during treatment (patented by the company) TG has slightly distorted layer-lattice structure as compared to the natural graphite, which could be responsible for transferring less beneficial film under severe operating conditions. SEM and EDAX studies were conducted to understand wear mechanisms. Such composites with such high PVlimit values low, µ (0.04) and low wear rates (1×10−16 m3/Nm) are not reported in the literature and may prove as ideal materials for dry bearings in harsh operative conditions.

The paper presents on the synergistic effect of two solid lubricants viz. thermo-graphite (TG) and hexa boron nitride (hBN – white graphite) in the composites when performance was evaluated in adhesive (against smooth mild steel disc) and in abrasive (against SiC paper) wear modes. The basic composition of matrix PEK (polyether ketone) (50%) and short glass fibers (30%) was kept constant and composites were designed with increasing amount of hBN (0, 5, 10, 15 and 20%) with simultaneous decrease of TG (20, 15, 10, 5 and 0). The composites were characterized for mechanical and tribological properties (in adhesive and abrasive wear modes). It was observed that the composites showed very good tribo-potential (very low wear rate and low friction) in adhesive wear mode. However, any of the SLs did not show great potential when included in isolation. Both showed synergism when existed in the composite in combination. The optimum amount was wear mode specific. For adhesive wear mode 15% TG and 5% hBN worked best while for abrasive wear mode 10% of each worked best. Overall TG proved better choice than hBN. Natural graphite proved superior to TG in adhesive wear mode, while trend was opposite for abrasive wear mode. The Lancaster–Ratner factor was observed to be responsible for controlling wear behavior.

The performance of iron boride coatings on carbon steel (cs) produced through thermal diffusion was investigated under tribo-corrosion conditions and compared with bare CS and 316L stainless steel. The tribological experiments involved reciprocating tests under both dry sliding and tribocorrosion conditions with a ball-on-flat geometry. The coatings demonstrated enhanced wear resistance primarily due to higher hardness and chemical inertness of the iron boride protective layer. Multi-layered structure of h-BN or other BN based compounds above the boronized steel reduced the ability for crack propagation as well as promoting a decrease in the friction coefficient (COF) by approximately 20%–40%, compared to CS. The microstructure and surface morphology of the worn surfaces were evaluated, which allowed better understanding the tribo-corrosion mechanisms in tested samples.

The current work focusses on the designing and manufacturing process followed by tribo-evaluation of high-performance polymeric bearings based on tribo-optimized composition in earlier work on pin on disc configuration. A series of bearings was developed by a combination of graphite (10 wt%) as a primary lubricant and particles of metal chalcogenides (MoS2 and WS2) in micro and nano-form as secondary lubricants (10%) into Polyaryl ether ketone (PAEK) matrix (50%) reinforced by 30% glass fibers (GF). Tribo-performance assessment of bearings against shaft was critically done and performance of the product (bearing) and material (pin against disc) was critically compared to understand the difference in performance, from material to the product.

The three composites based on poly (aryl ether ketone) (PAEK) (60 wt %) as a matrix, glass fibers (30 wt %) as a reinforcement and particulate graphite 10 wt % as a solid lubricant were developed with identical composition but differing in the size and hence surface area of graphite particles. The theme of research was to study the influence of size of particles on physical, mechanical and tribological performance of the composites. Graphite particles possess a layer lattice structure which provides efficient lubrication and also enhanced thermal conductivity. The distribution of graphite particles and glass fibers in the bulk of composites was observed using X-ray micro-tomography. All the composites exhibited excellent tribo-performance indicating μ ≈ 0.04, and wear rate ≈10−16 m3/Nm apart from very high PVlimit values (≈112 MPa m/s). Composite containing graphite with smallest particle size (4 μm) performed best, followed by the one with medium size (15 μm). Scanning electron microscopy (SEM), as well as energy dispersive x-ray (EDAX) studies were conducted to observe the transfer film distribution and the wear mechanism. Postmortem analysis on the worn surfaces were performed by Raman spectroscopy. Chemical composition of the lubricating film on the worn disc surface was studied using x-ray photoelectron spectroscopy (XPS).

Graphite is one of the most widely used solid lubricants in both, anti-friction and friction materials. The influence of particles in the composite mainly depends on its size, amount, its combination with fibers and other fillers etc. No efforts were done to optimize the amount of graphite to achieve very low friction and wear. A series of Polyaryl ether ketone (PAEK) composites with GF (short glass fibers) and increasing amount of graphite particles (10, 15, 20 and 25 wt %) were developed and characterized for various properties such as physical, mechanical, thermal along with adhesive wear performance in severe operating conditions (high pressure and velocity (PV)). Inclusion of graphite led to deterioration in strength and modulus but increase in thermal conductivity. The composites showed very low μ (friction coefficient) in the range of 0.04 and K0 (specific wear rate) (∼2 × 10−16 m3/Nm). Composite with 15 wt % graphite proved to be significantly superior by showing highest PVlimit value (154 MPa m/s) and very low μ (0.04) and K0 (1.91 × 10−16 m3/Nm). The typical inferences were supported by various techniques such as Scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), 3D profilometer, Raman spectroscopy on the worn surfaces.

The attempt to explore the tribo-potential of micro-particles and nano-particles of Boric acid, a well know solid lubricant with a layer lattice structure is first time reported in this work using high performance poly (aryl-ether-ketone) (PAEK) as a matrix, short glass fibers (GF) as a reinforcement and graphite as a primary solid lubricant. The tribo-performance evaluation in a pin on disc configuration under high pressure and velocity conditions confirmed very low μ and specific wear rates (around 0.04–0.08 and 2–8 × 10−16 m3 (Nm) respectively for these composites. Slight deterioration in performance due to particles was analyzed based on the degradation chemistry of boric acid at high temperature. The test results were discussed by considering the surface properties, i.e., material removal and film transfer formation. Scanning electron microscopy, energy dispersive x-ray analysis and Raman spectroscopy on worn surfaces was performed to understand wear mechanisms.