Si3N4 Ball Research Articles

Microstructure and Wear Resistance of FeCrV15 Coatings by Laser Cladding

Improving the surface performance and service life of 60Si2Mn steel is an important issue in agricultural machinery. A FeCrV15 coating layer may exhibit excellent performance in wear resistance. This research focuses on studying the microstructure and wear resistance of the FeCrV15 coating layer at various scanning speeds through laser cladding. Microstructure, phase distribution, surface hardness, and wear resistance of the coating layers are analyzed using X-ray diffraction (XRD), scanning electron microscopy (SEM), a microhardness tester, and laser confocal microscopy. The results indicate that the FeCrV15 alloy coating consists of γ-Fe, V8C7, and Cr7C3. The microhardness of the FeCrV15 coatings increases with the increase in the scanning speed. At a scanning speed of 8 mm/s, the highest microhardness reaches 727.5 ± 27 HV, approximately 2.5 times higher than the substrate. The friction and wear test of the coating is conducted using a 4 mm diameter Si3N4 ball grinding pair. The coatings prepared at different scanning speeds exhibit lower average coefficients of friction and wear rates compared to the substrate. Both the average coefficient of friction and wear rate decrease with increasing scanning speed. At a scanning speed of 8 mm/s, the lowest average coefficient of friction and the lowest wear rate were observed. The main wear mechanisms of the coating are oxidative wear and adhesive wear, with a small amount of abrasive wear.

Investigating on the Tribological Behavior of Binderless WC Matrix Composite

The purpose of this study was to investigate the dry friction and wear behavior of WC-4.3wt.%MgO-2wt.%ZrO2 (WM2Z) composite. WM2Z composite prepared by high-energy ball milling and spark plasma sintering (SPS) technology exhibited excellent comprehensive mechanical properties and dense microstructure. Dry friction test results indicated that the increase of sliding speed will lead to the decrease of friction coefficient, while at the same sliding speed, the extension of sliding time has no significant effect on the friction coefficient. The wear volume increased proportionally with the sliding time, while the wear rate stabilized after reaching a certain duration. The wear mechanism was mainly slight abrasive wear. Additionally, some oxidation occurred on both the WM2Z composite and the Si3N4 ball during friction, forming an oxide film that contributed to the reduction of the friction coefficient. The novelty of this study lies in the first systematic investigation of the effects of sliding speed and time on the wear performance of WM2Z composite, and the revelation that in high-speed sliding environments, even with shorter sliding times, the material experiences faster wear. This discovery emphasizes the important role of sliding speed in the wear process and provides new insights into understanding the wear mechanism of materials in practical applications. This study not only enriches the friction and wear theory of binderless WC matrix composites, but also provides important experimental data and theoretical support for the design and application of related materials, laying a solid foundation for wear resistance optimization and industrial applications.

Impact of deposition pressure on the structural, nanomechanical, and tribological properties of δ-TaN coatings deposited via magnetron sputtering on Ti6Al7Nb alloy

In the present study, δ-TaN thin films were deposited by reactive magnetron sputtering (physical vapour deposition) on Ti6Al7Nb alloy by varying the deposition pressure (0.8–0.2 Pa). Their crystalline structure, chemical composition, surface roughness, and surface morphology were investigated by using grazing incidence X-ray diffraction, energy dispersive spectroscopy, scanning probe microscope, and field emission scanning electron microscopy (FESEM), respectively. Structural analysis results confirmed the deposition of cubic δ-TaN thin films along the (111) basal plane; moreover, spherical dome-like surface morphology was observed by FESEM. Further, to analyze the nanomechanical properties of the deposited δ-TaN coatings, such as hardness (H) and modulus (E), scratch tests were performed utilizing the nanomechanical system. Moreover, friction and wear properties of the coating and bare sample (substrate) were investigated on nano-tribometer equipment using a rotary ball-on-disk type configuration. The stainless steel (SS-316) and silicon nitride (Si3N4) balls were used as the counter materials for the tribological tests. The observations of nanomechanical tests revealed that H (GPa), E (GPa), and H/E ratio values increased from 11.83 to 28.30 GPa, 176.02 to 248.45 GPa, and 0.06 to 0.11, respectively, with the decrease of the deposition pressure. In the scratch test, the highest critical load (cohesion failure) was found for δ-TaN coating deposited at the lowest deposition pressure (0.2 Pa). Tribological results of δ-TaN coatings demonstrated average coefficient of friction (COF) value ranges between 0.066–0.092 and 0.072–0.029 against steel and Si3N4 balls, respectively. The wear rate values were observed to vary from 8.15 × 10−5 to 7.56 × 10−6 and from 1.77 × 10−3 to 8.99 × 10−6 against steel and Si3N4 balls, respectively. Generally, the average COF and wear rate decreased against 316 SS and Si3N4 balls as the deposition pressure of coatings decreased. However, the coating deposited at 0.8 and 0.6 Pa against Si3N4 ball showed early delamination of the coating, resulting in the sudden fluctuation in COF plots and higher wear rate in the range of 10−3 mm3/N.m.

Fabrication and assessment of dry sliding behavior of Ti3C2Tx-MXene reinforced nickel aluminide composites

MXene has been recognized globally for its ability to act as a solid lubricant, lubricant additive, and protective coating for enhancing the performance and longevity of dynamics systems. Ni3Al matrix composites have been fabricated through spark plasma sintering with varying Ti3C2Tx-MXene concentrations and slid against the Si3N4 ball to evaluate the lubrication potential at atmospheric conditions. The addition of MXene in the matrix has improved anti-friction and anti-wear properties attributed to the formation of a tribo-layer on encountering surfaces consisting of oxides and MXene’s fragments, as confirmed by TEM and Raman spectroscopy. However, further increasing MXene to 20 % led to an increase in friction, ascribed to the dominance of the hard TiC phase, which acts as a barrier for tribo-layer formation.

Impact of Relative Humidity on the Formation of Low-Frictional Interface and its Continuity in Tribological Systems with Hydrogenated Carbon Nitride Coatings

The impact of relative humidity on the formation of low-frictional interface in hydrogenated carbon nitride (CNx:H) coatings sliding against Si3N4 balls and the formation continuity was elucidated through friction tests conducted in both air and nitrogen atmospheres with controlled relative humidity levels. In air atmosphere, a carbonaceous tribolayer with a transformed structure from the initial CNx:H was formed on Si3N4 at less than the critical humidity that existed in 1.0–3.0% RH, resulting in low friction (μ < 0.05) and a low specific wear rate of the balls (< 2 × 10–9 mm3/N·m). In contrast, this tribolayer failed to form above 3.0% RH. In nitrogen atmosphere, within the 0.25–1.0% RH range, the tribolayer continued to form concurrently with wear progression, maintaining low friction for over 50,000 cycles. However, in less than this humidity range, the lifetime of low friction was limited owing to the tribolayer’s structural alteration. Thus, relative humidity influences not only the formation of the low-frictional interface but also the formation continuity. On the CNx:H friction surface, hydrogen, hydroxyl, and oxygen groups from environmental water and oxygen molecules continued to chemisorb owing to tribochemical reactions on the uppermost few nanometers during continuous low friction in a nitrogen atmosphere, while hydrogen content of CNx:H desorbed. This study experimentally confirmed the critical role of controlling relative humidity in tribological systems using CNx:H coatings to achieve low friction and improve its durability of low friction through the continuous formation of the low-frictional interface.

The self-lubrication property of single-phase high-entropy carbide ceramic under tribo-induced effect

Self-lubricating ceramic materials are mainly achieved through the addition of lubrication phases. Although incorporating lubrication phases can improve their tribological performances, the mechanical properties are consistently compromised. Thus, designing and fabricating single-phase ceramic with favorable self-lubricity is the relentless pursuit of researchers. In this study, the single-phase high-entropy ceramic of (Hf0.2Mo0.2Nb0.2Ta0.2Ti0.2)C exhibits self-lubricating properties and which closely relates to the testing condition. The wear rate and friction coefficient decrease with the increasing of loads (not above 30 N). And the friction coefficient of (Hf0.2Mo0.2Nb0.2Ta0.2Ti0.2)C samples against Si3N4 balls is as low as 0.3 under 30 N and 5 Hz. This originates from the carbon-rich tribo-film with self-lubricity, which is generated through diffusion and enrichment under the effect of tribo-induced. Single-phase self-lubricating ceramics—using own constituent elements to form a lubricating tribo-film—are expected to open up a new research field on the high-performance friction materials.

Improved tribological behavior of Ti-6Al-4V through a novel zirconium diffusion coating

Titanium alloys, especially Ti-6Al-4V, are widely applied in the aerospace, automotive, marine, medical, and chemical industries due to their high strength, low density, good corrosion resistance, and high-temperature performance. However, the low wear resistance of Ti-6Al-4V hinders its broader applications. In this study, the influence of five different surface modifications on the tribological behavior of Ti-6Al-4V is compared. The five surface modifications were categorized as: 1) single-step process (oxidation), 2) two-step process (oxidation+reduction), 3) three-step process (oxidation+reduction+reoxidation), 4) oxidation at reduced oxygen partial pressure, and 5) a newly developed Zr slurry diffusion coating followed by subsequent oxidation to form ZrO2-enriched TiO2 on the surface. The wear tests were performed using a Si3N4 ball counterpart with a load of 5 N at a sliding velocity of 5.25 · 10−2 m/s and with a total sliding distance of 300 m. The wear mechanism for the unmodified Ti-6Al-4V was predicted and observed to be the detachment of Si3N4 particles from the counterpart and metallic particles from the substrate, subsequent oxidation of these particles via tribochemical reactions, and the adherence of the oxidized wear debris into the substrate and counterpart surface grooves. Deep ploughing grooves were not evident in the wear tracks of any surface-modified Ti-6Al-4V materials. Instead, wear debris containing Si-rich oxides formed as a tribolayer, except for the two-step processed sample. All surface treatments led to narrower and shallower wear tracks and there was no measurable material removal for the Zr diffusion-coated sample under the investigated conditions.

Effect of cryogenic duration on the tribological properties of sintered polycrystalline c-BN during sliding mating materials in vacuum

The service performance of polycrystalline cubic boron nitride (PcBN) tools undergoes significant changes due to the deep space environment to the structure and wear behaviors of PcBN. In this paper, the effect of cryogenic treatment (CT) was studied to investigate the physical and tribological behaviors of PcBN. The hardness and wear resistance of PcBN are improved but wear forms are not affected, which are abrasive wear. The shedding of cBN played the role of micro-cutting edges, carving furrows on surfaces. As the CT duration increases, the wear rate of PcBN decreases from 2.56 × 10−8 mm3/N mm to 1.61 × 10−8 mm3/N mm for sliding against Si3N4. When PcBN slid Al2O3, the lowest wear rate is 1 × 10−8 mm3/N mm which the decline reached 34 %. Due to discrepancies in physical and mechanical properties, Si3N4 and YG8 balls exhibit abrasive and adhesive wear, and Al2O3 shows fatigue wear. Until the fatigue failure appeared, Al2O3 exhibited the lowest wear rate of 2.30 × 10−9 mm3/N mm. Among three materials, the wear rate of Si3N4 was the highest. By calculating the wear rate ratio of the materials, it was concluded that the optimal removal efficiency was achieved for Si3N4 and YG8 when CT duration is 24 and 48 h, respectively.

Tribological Behavior of Polydiethylsiloxane (PDES) in a Si3N4 and M50 System under Low Temperatures from −80 to 25 °C

Lubricants must exhibit good tribological behavior at low temperatures to ensure reliable startups in very cold regions. This study investigates the performance of lubricants, with a specific focus on their capacity for high-temperature lubrication and ensuring reliable low-temperature startup in engines. Experiments were conducted to assess the friction and wear characteristics of polydiethylsiloxane in conjunction with a Si3N4 ball and M50 (8Cr4Mo4V) steel across a temperature range of −80 °C to 25 °C. The results indicate that the coefficient of friction, as determined through friction and wear tests at various temperatures, remained below 0.1. As temperatures progressively decreased, the system’s friction coefficient increased, and wear volumes recorded at 25 °C and −60 °C were 9749.513 µm³ and 105.006 µm³, respectively, culminating in lubrication failure at −100 °C. This failure is primarily attributed to the increased viscosity and decreased mobility of polydiethylsiloxane at extremely low temperatures. Additionally, the reduced temperature increases the strength of the quenched steel, leading to hard particles or protrusions on the material’s surface, which collide with the Si3N4 ball during friction, causing adhesion and spalling. Despite this, polydiethylsiloxane forms a stable protective oil film on the surface, enhancing the system’s lubrication performance. However, below −80 °C, this oil film begins to tear, leading to diminished lubrication efficacy. This study provides valuable data supporting the field of cryogenic lubrication.

High-Temperature Tribological Behavior of Fast-Hot-Pressed NiCr/Cr3C2-LaF3 Self-Lubrication Composite

This article details a method for preparing cermet matrix composites via Fast hot pressing (FHP) sintering technology and emphasizes their potential use in extremely high-temperature settings. The material primarily consists of NiCr alloy, Cr3C2, and LaF3. An in-depth investigation was conducted on the tribological properties of the specimen by conducting sliding tests against a Si3N4 ball at varying temperatures, including room temperature (RT), 400 °C, 600 °C, and 800 °C. Advanced techniques such as scanning electron microscopy, micro-XRD, and micro-Raman spectroscopy were employed to examine the friction surfaces formed under different frictional temperatures. The findings reveal a uniform composition and high density within the composites. It is noteworthy that as the LaF3 content increases, the hardness of the ceramic phase diminishes. Conversely, the hardness of the alloy phase augments with the addition of LaF3, provided that its content remains below 15 wt%. The composite material containing 15 wt% LaF3 demonstrates superior hardness values, with the ceramic phase reaching HV1412 and the alloy phase achieving HV384. Furthermore, the coefficient of friction of the composite material was evaluated. The coefficient of friction of the composite is between 0.74 and 0.4 and the wear rate is 4.46 × 10−6–5.72 × 10−5 mm3N−1m−1 from room temperature to 800 °C. The lubrication behavior at low temperature is mainly attributed to the lubricating effect of LaF3, and at high temperature it is due to the tribochemical reaction to form LaCrO3 with good lubricating properties, which plays a synergistic lubricating role with Cr2O3.

A Novel Al-Al&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;3&lt;/sub&gt; Non-Skid Composite Coating with Improved Wear Resistance Fabricated by Twin Wire Arc Spraying

In this study, novel non-skid Al-Al&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;3&lt;/sub&gt; coatings with improved wear resistance were fabricated using twin wire arc spray (TWAS). TWAS Al coating was prepared as a reference sample and representative TWAS parameters (working distance, process gas pressure, arc current) were controlled to fabricate different Al-Al&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;3&lt;/sub&gt; coatings. The Al-Al&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;3&lt;/sub&gt; coatings showed a superior static coefficient of friction and higher surface roughness than the Al coating. The microstructural analysis of the Al-Al&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;3&lt;/sub&gt; coatings revealed that the coatings contained Al splats, partially-melted Al&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;3&lt;/sub&gt; particles, fully-melted Al&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;3&lt;/sub&gt; splats and pores. The porosity and Al&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;3&lt;/sub&gt; content of the Al-Al&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;3&lt;/sub&gt; coatings varied with different process parameters. The Vickers hardness of the Al matrix showed a similar value in all samples, which means the deposition phenomena was the same. Ball-on-disc wear test with a Si3N4 ball was used to evaluate the wear resistance of the TWAS coatings. The weight loss of the Al-Al&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;3&lt;/sub&gt; coatings were only 4.8 ~ 17.0 % of the Al coating, indicating that the wear resistance of the TWAS Al-Al&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;3&lt;/sub&gt; coatings was superior. The TWAS coatings showed a complex wear mechanism, such as splat wear and abrasive wear. The distributed Al&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;3&lt;/sub&gt; particles in Al-Al&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;3&lt;/sub&gt; coating successfully suppressed the abrasive wear of the Al matrix, which contributed to the enhanced wear resistance. The results in this study indicated that the Al-Al&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;3&lt;/sub&gt; composite coating has potential use as a novel non-skid coating.

Study on High-Temperature, Ultra-Low Wear Behaviors of Ti6Al4V Alloy with Thermal Oxidation Treatment

Thermal oxidation (TO) is a simple and economical way to enhance the wear resistance of the Ti6Al4V alloy. The TO temperature has a very important effect on the tribological properties of the TiO2 layer formed. However, the impact of the oxidation temperature on the high-temperature tribological behavior of a TO-treated Ti6Al4V alloy is not clear. Therefore, the Ti6Al4V alloy was oxidized at 400 °C, 600 °C, and 700 °C for 36 h, and the sliding friction experiments were conducted at room temperature (RT) and 400 °C with a Si3N4 ball as the counter body to comparatively study the effect of the oxidation temperature on the high-temperature friction behavior of the TO-treated Ti6Al4V alloy. The results show that the TO treatment can effectively improve the wear resistance of the samples at both room and high temperatures. Among them, the oxidation-treated samples at 700 °C show the best wear resistance, with a reduction of 92.6% at high temperatures; the amount of wear loss at room temperature was so small that it was almost incalculable. At room temperature, the friction surface formed uneven agglomerate formations, resulting in an elevated coefficient of friction (CoF) compared to the untreated samples. At a high temperature, however, the CoF is reduced compared to the untreated samples due to the formation of a homogeneous transfer film in the wear area that is caused by the interaction of Si3N4 and oxygen.

A novel wear-resistant and corrosion-resistant Mo2NiB2–Ni cermet coating prepared using fast hot pressing sintering

A new fast hot pressing (FHP) sintering method was used to prepare Mo2NiB2–Ni cermet coating to solve the problems of small scale and high energy consumption in the production. The synthetic phase and microstructure of the Mo2NiB2–Ni cermet coating were studied, and friction and wear as well as electrochemical corrosion performance were also tested. The results indicated that the Mo2NiB2–Ni cermet coating was composed of two phases, the Mo2NiB2 hard phase and the Ni metal-bonded phase. A metallurgical bond interface resembling interlocking teeth was formed between the Mo2NiB2–Ni cermet coating and the stainless steel substrate, thereby enhancing the bonding strength of the interface. Compared with the Mo2FeB2–Fe cermet coating, the Mo2NiB2–Ni cermet coating had certain wear resistance and excellent corrosion resistance. The high hardness of the Mo2NiB2 hard phase, the low mutual solubility between the Ni metal-bonded phase and the Si3N4 balls, and the generated mechanical mixing layer reduced the friction coefficient and the adhesive wear, which improved the wear resistance. The higher open circuit potential and the formation of the passivation film during the corrosion process enhanced the corrosion resistance of the Mo2NiB2–Ni cermet coating.

Ultralow friction and low wear behavior of in-situ formed NiTiO3 from 60NiTi alloy at 350 °C

Self-lubricating materials of NiO–TiO2 binary system have been rarely studied. In this paper, the friction experiments between 60NiTi discs and Si3N4 balls under dry friction conditions were carried out in ambient air from room temperature (RT) to 400 °C. The mechanical properties of each phase of 60NiTi after the friction experiments at different temperatures are measured by nanoindentation tests. The results show that the mechanical properties of the NiTi2 phase are best, and overall mechanical properties of 60NiTi get worse at 400 °C. The coefficient of friction (CoF) and wear rate basically drop from RT to 350 °C and rise at 400 °C. The behavior of ultralow friction and low wear is achieved at 350 °C with a CoF of 0.069 and a wear rate of 0.990 (mm3/mN) × 10−5. As temperature rises, the in-situ formed NiTiO3 ceramic plays a key role in improving tribological properties. The friction mechanisms at different temperatures are discussed systematically.

Charge-induced ultralow friction between graphite and atomically flat surfaces

Reaching near-zero friction is one of the jewels on the crown of tribology, and structural superlubricity is a crucial mechanism to achieve it. Previous works focus mainly on the structural superlubricity at incommensurate crystalline interfaces. However, realizing such interfaces on a large scale without defects and contaminations is a formidable challenge. Here, we report a charge-induced robust macroscale superlubricity between graphite and atomically flat surfaces in the ambient condition. We transferred graphite flakes on Si3N4 balls and used them to measure the friction properties on pristine and charged atomically flat surfaces such as 300 nm SiO2/Si and sapphire. We found that the surface charge can dramatically reduce the coefficient of friction between graphite and substrates by two orders of magnitude to 10−4, and the sliding is wearless even under harsh contact conditions (∼1.1 GPa center pressure and >100 m). We demonstrate that the surface charge is critical in achieving superlubricity possibly because it can reduce adhesion between graphite and substrate surfaces and make the substrate surfaces resistant to contaminations. Our method offers a ready-to-use solution to superlubricity alternative to achieve incommensurate crystalline interfaces. Thus, it can reduce the difficulty of realizing macroscale superlubricity for applications.

Wear performance of Ni-WC composites and heat-damage behaviour of WC particle during vacuum-induction melting process

Ni-WC composites were prepared by vacuum-induction melting (VIM). A ball-on-disc wear test was performed using an Si3N4 ball as a friction pair to study the wear performance of the composites. The effects of WC particle size (average particle size of 68 μm and 23 μm) on the mechanical properties of the composites and the heat-damage behaviour of WC particles during the melting process were investigated. The results indicate that the wear rate of Ni-WC composites with coarse WC particles was lower than that of Ni-WC composites with fine WC particles. The predominant wear mechanism of composites with coarse WC particles was mechanical wear of the WC particles; the predominant wear mechanisms of composites with fine WC particles were oxidation wear and three-body abrasive wear. The coarse WC particles provide better wear resistance than fine WC particles. The WC particles underwent heat erosion and dissolution caused by the Ni-based melt. Increasing the size of the WC particles can significantly reduce the degree of heat damage to the WC particles and improve the hardness of the composites.

Friction and wear behaviors of boron-containing high entropy alloy/diamond composites

In present work, FeCoCrNiB0.15 high-entropy alloy (HEA) with its diamond composite were prepared by spark plasma sintering (SPS) technique at 950 °C. FeCoCrNiMo0.15 and its diamond composite samples were prepared for comparison. The phase composition and microstructures of FeCoCrNiMo0.15 and FeCoCrNiB0.15 HEAs and diamond composite samples were investigated, and the friction and wear behaviors of the HEAs and diamond composites against Si3N4 balls under dry sliding condition in ambient air were compared on a ball-on-disk tester. The results showed that, Cr-rich phase precipitated from the metastable FCC matrix was observed in both HEAs. The relative density of the FeCoCrNiMo0.15 and FeCoCrNiB0.15 alloy samples was ∼93.1 % and ∼ 98.4 %, respectively, while the Vickers hardness of the samples was 309.7 ± 10.6 HV1 and 317.5 ± 8.4 HV1, respectively. The wear resistance of FeCoCrNiB0.15 was higher than that of FeCoCrNiMo0.15 alloy, and the grinding rate of FeCoCrNiB0.15/diamond composite against Si3N4 was higher than that of the FeCoCrNiMo0.15/diamond composite. With detailed microstructural analyses, the possible friction and wear mechanism were discussed. Present study shows that the boron-doped HEA matrix in diamond composites is a promising candidate for fabricating diamond tools with long service life and high processing efficiency.

Effect of strontium sulfate on microstructure and high-temperature tribological properties of Co matrix composites

To enhance the resistance to wear of Co matrix alloy as high-temperature hot-end parts, the Co-based composites reinforced by strontium sulfate (4.0, 9.0 and 14.0 wt%) were prepared by using a powder metallurgy technology (P/M). The effects of SrSO4 on the microstructure, phase and tribological properties of composites were systematically investigated. The tribological behaviors of Co-based composites were tested from room temperature to 800 °C against Si3N4 ball by a ball-on-disk tribo-tester. The results indicated that SrSO4 decomposed during sintering, and the tribological properties of composites were improved by the addition of SrSO4. The composite with 9.0 wt% SrSO4 had favorable tribological behavior, which was attributed to the in-situ synthesized solid lubricants and lubricating film formed on the contact surfaces.

Improved dry sliding wear behavior of TA1titanium by low-temperature plasma nitriding by CCPN method

Cathodic cage plasma nitriding (CCPN) has been proven a promising technique to improving titanium’s poor wear resistance at a relatively lower temperature. Nonetheless, less attention has been paid to the performance of the treated sample at the cathodic potential by CCPN process, mostly on the sample at the floating potential. It has been demonstrated that a nitrogen diffusion layer is formed other than compound layer at the cathodic potential, which is beneficial to improve the bearing-load capacity and adhesion strength between the modified layer and the substrate. In this study, a cathodic cage in combination with pulsed-biased system has been used to realize nitriding of TA1 titanium at the cathodic potential below 660 °C. The influence of pulsed current and treatment time on the resulting surface microstructure and wear performance when sliding against Si3N4 balls were studied. Results showed that with the increasing pulsed current and prolonged processing time, the nitride layer thickness, hardness and roughness also increase. Additionally, although the anti-wear resistance is considerably improved through nitriding treatment compared to untreated TA1 titanium, and there are still differences between the samples prepared under different nitriding parameters. Lastly, the optimum pulsed current and processing time of the CCPN process that provide the best tribological characteristics are determined.

Effect of V doping on the high temperature tribological properties of (Ti1−xVx)3AlC2 solid solutions sliding against different counterparts

The effects of Al content and the counterface material on the high temperature tribological behavior and wear mechanism of (Ti,V)3AlC2 solid solutions were investigated. The friction coefficient of (Ti0.6V0.4)3AlC2 is reduced by 36.25% and 47.76% compared to Ti3AlC2 at room temperature and 800 °C respectively. When coupled with Al2O3 and ZrO2 balls at 800 °C, continuous smooth lubricating films composed of oxides formed by the tribochemical reaction lead to the lower friction coefficients. When coupled with Si3N4 and SiC balls, the wear rates are relatively low due to the formation of friction films containing SiOx.