Si3N4 Ball Research Articles

Development of two directional beam steering ECH/CD launcher for JT-60SA

Developments of a two directional beam steering electron cyclotron heating/current drive launcher for JT-60SA have been progressed based on a linear motion antenna concept. A full-scale (˜7 m) mock-up of the mirror steering structure with two kinds of bellows structures and an in-vessel support structure has been fabricated and tested in vacuum successfully. The support structure consists of a pair of angular ball bearings made of Si3N4 for rotational motion and a linear guide assembled by a rail and a housing made of non-magnetic stainless steel and Si3N4 balls. Solid lubricant has been used for the linear guide and it results in the improvement of the life time by a factor greater than 10 with respect to the case without lubricant. Considering that the mock-up test results satisfied the requirements for the bellows and support structures (reliable 40 cm linear movement, 105 cycles and angular rotation 30°, 104 cycles), the final design of the launcher is underway targeting the start of its fabrication.

Tribological Properties of Cr(Si)CN Coatings Sliding Against Different Mating Balls in Water

Chromium carbon nitride coatings have potential industrial applications in aqueous environments due to their good tribological properties and corrosion resistance. In order to reveal the effect of silicon doping on the tribological properties of CrCN coating, the tribological properties of Cr(Si)CN coatings sliding against potential sliding partners (Si3N4, Al2O3 and SUS440C balls) in water were discussed. The results showed that the coefficient of friction (COF) for different partners could be arranged as μAl2O3 < μSi3N4 < μSUS440C regardless of coatings. This result was determined by the tribochemical reaction, oxidation resistance and contact pressures of tribopairs. After the incorporation of Si element, the friction behavior of CrCN coating was improved due to the friction-induced hydration of amorphous silicon compound phase as sliding against Si3N4 and SUS440C balls.

Effects of environmental atmospheres on tribological behaviors of sintered polycrystalline diamond sliding against silicon nitride

To explore the effect of various atmosphere the tribological behaviors of the sintered polycrystalline diamond compacts (PDCs), the friction and wear behaviors of PDCs sliding against Si3N4 balls were evaluated by a ball-on-disk tribometer under nitrogen, argon, oxygen and air (10% relative humidity) environments, respectively. The energy dispersive X-ray spectrum (EDS), Raman spectroscopy, scanning electron microscopy (SEM) and atomic force microscope (AFM) were conducted to investigate the microstructure evolution of worn surface. The results demonstrated that the low friction appeared in argon and nitrogen environment. The formations of consecutive carbonaceous transfer films on wear scars contributed to decrease the friction during sliding process. The wear of PDCs and Si3N4 balls were serious in argon and nitrogen environment, but slight in oxygen and air conditions. There is a direct relationship between material removal and running-in period. The passivation effect of dangling bond under oxygen and air conditions can shorten the running in period thus weaken the wear.

Effect of self-developed graphene lubricant on tribological behaviour of silicon carbide/silicon nitride interface

The research presented in this paper aims to investigate the effectiveness of different surface roughness and lubrication conditions on the interfacial tribological properties between silicon carbide (SiC) and silicon nitride (Si3N4) ceramics, particularly for providing insight into the mechanisms of how graphene reduces the friction and wear rate. The worn groove topography and surface composition were characterised in detail with 3D laser measuring microscopy and X-ray photoelectron spectroscopy. The tribological test results on the UMT-TriboLab show that a smooth initial surface is more likely to obtain a low friction coefficient and wear rate under water lubrication. The proper initial surface roughness for SiC and Si3N4 ceramics is approximately Ra 10 nm, and it will be lower in an alcohol or graphene aqueous solution. A large load does not worsen the tribological behaviour of a Si3N4 ball sliding against a SiC disk, and it reduces the friction coefficient and wear rate. Among the five lubrication states of dry friction, dry graphene lubrication, water lubrication, graphene solution lubrication, and self-developed graphene lubrication, the self-developed graphene lubricant can exhibit an ultra-low friction coefficient of 0.009 and ultra-low wear rate of 1.69 × 10−7 mm3/N·m. The excellent tribological property of the graphene-coated ceramic surface helps the prepared lubricant to decrease the friction coefficient effectively. Furthermore, the graphene film can protect the SiC from being oxidised by water under the tribo-activated action, and therefore, lead to ultra-low wear rate under low friction condition. Alcohol improves the tribological property of the self-developed graphene lubricant, mainly because of the good wettability between graphene and ethanol. The self-developed graphene lubricant can be applied in water-lubricated ceramic bearings and motorised precision spindles.

Self-repairing effect of few Si3N4 balls used as rolling elements to enhance the performance of bearings operating under contaminated lubrication conditions

The performance of the rolling element bearings operated at contaminated lubricant environment was simulated and analyzed in this research work. Artificial surface pits were created on the rolling element bearing inner track contact surface to simulate the effects of solid particle contaminants. The rolling element bearing consists of two Si3N4 balls in compliment with regular steel balls has completed the defined test cycles. The Post-test surface analysis confirmed that the Si3N4 balls had deformed the stress risers. The ball-on-disc experiment was conducted to simulate the repair mechanism produced by Si3N4 balls. The Finite element method was utilized to understand the failure mechanism of the bearing. The higher stress concentration was observed at the edges of the artificial pits.

Towards Functional Silicon Nitride Coatings for Joint Replacements

Silicon nitride (SiNx) coatings are currently under investigation as bearing surfaces for joint implants, due to their low wear rate and the good biocompatibility of both coatings and their potential wear debris. The aim of this study was to move further towards functional SiNx coatings by evaluating coatings deposited onto CoCrMo surfaces with a CrN interlayer, using different bias voltages and substrate rotations. Reactive direct current magnetron sputtering was used to coat CoCrMo discs with a CrN interlayer, followed by a SiNx top layer, which was deposited by reactive high-power impulse magnetron sputtering. The interlayer was deposited using negative bias voltages ranging between 100 and 900 V, and 1-fold or 3-fold substrate rotation. Scanning electron microscopy showed a dependence of coating morphology on substrate rotation. The N/Si ratio ranged from 1.10 to 1.25, as evaluated by X-ray photoelectron spectroscopy. Vertical scanning interferometry revealed that the coated, unpolished samples had a low average surface roughness between 16 and 33 nm. Rockwell indentations showed improved coating adhesion when a low bias voltage of 100 V was used to deposit the CrN interlayer. Wear tests performed in a reciprocating manner against Si3N4 balls showed specific wear rates lower than, or similar to that of CoCrMo. The study suggests that low negative bias voltages may contribute to a better performance of SiNx coatings in terms of adhesion. The low wear rates found in the current study support further development of silicon nitride-based coatings towards clinical application.

Enhanced tribological behaviors of sintered polycrystalline diamond by annealing treatment under humid condition

The tribological behaviors of the 700 °C annealed sintered polycrystalline diamond (PCD) at various relative humidity (RH) levels were systematically investigated. The comparison of tribological behaviors between the 700 °C annealed PCD and the pristine PCD was made to further understand the tribological mechanisms. The results reveal that the friction inducing carbonaceous transfer film and oxidation and hydrolysis induced tribochemistry reaction dominant the tribological behaviors of the annealed PCD at various RH levels. The low coefficient of friction (COF) obtained in dry environments is attributed to carbonaceous transfer film on the worn Si3N4 surface, which was formed by the layers shearing action of massive tiny diamond grains exfoliated from the annealed PCD surface. The graphitization, oxidation and stress relaxation of the PCD induced by the 700 °C annealing treatment make the tiny diamond grains more easily to exfoliate and be grinded on the Si3N4 interface. It facilitates the formation of friction reducing carbonaceous transfer film, and finally results in the 30% lower COFs than those of pristine PCD at low RH levels (5%–50% RH). Meanwhile, an enhanced wear resistance of PCD can be achieved after 700 °C annealing treatment. The tribochemistry reaction induced by the oxidation and hydrolysis of Si3N4 governs the tribological behaviors of the annealed PCD at high RH levels (60%–99.9% RH). It reveals higher COFs accompanied with serious wear of Si3N4 ball and nearly no wear loss of annealed PCD. The produced SiO2 and silicic acid embeds into massive spalling pits on the annealed PCD surface, resulting in slighter wear of the PCD and Si3N4 than that of the pristine PCD/Si3N4. These results propose that the tribological behaviors of PCD under humid environment can be significantly improved by the 700 °C annealing treatment.

Characterization of ZrN coating low-temperature deposited on the preliminary Ar+ ions treated 2024 Al-alloy

The present paper considers the problem of the low-temperature deposition of the hard coatings on the alloys having a low melting point and a high affinity for oxygen, like aluminum or magnesium alloys. It is demonstrated that a hard ZrN coating can be produced on the 2024 aluminum alloy by the low-temperature vacuum-arc deposition method. To achieve high adhesion strength between the coating and substrate, the substrate was sputtered by low-energy inert Ar+ ions before the deposition process in order to remove the natural oxide layer. The optimal technological regimes selected and used allowed obtaining the stoichiometric ZrN coating of extremely low roughness (0.061 μm), uniform thickness (~1 μm) with nano-scale columnar microstructure with the cross-sectional size of the columnar grains of ~20–50 nm. The layered microstructure of the obtained coating respectively consisted of the columnar and V-shaped grains in the lower and upper layers comes to be in the ‘transition zone’ on the ‘structure-zone diagram’. The lower layers consist of a number of AlxZry phases along with the Zr3N4 orthorhombic phase, while the outmost layer of the film contains the single ZrN fcc phase. In comparison with the substrate alloy, the produced ZrN coating is shown to possess the superior anti-corrosion properties in saline solution, a high hardness (~20 GPa) and elastic modulus (196 GPa), high adhesion strength both at the progressively increased load and at cyclic dry sliding of the conical diamond indenter with the 50 μm tip, low friction coefficients and high wear resistance at the reciprocating sliding both in the dry and wet (liquid paraffin) conditions against the conical diamond indenter with the 50 μm tip and 8 mm Si3N4 ball, respectively.

Microstructure, wear and corrosion behaviors of plasma sprayed NiCrBSi-Zr coating

The properties of thermal sprayed alloy coatings are highly affected by the splat interfaces. NiCrBSi-Zr coating was prepared by atmospheric plasma spraying using NiCrBSi mixed with ZrH2 feedstock. NiCrBSi coating was also prepared under the same condition for comparison. The microstructure as well as the splat interfaces of the NiCrBSi and NiCrBSi-Zr coatings was analyzed. The friction and wear behaviors of both two coatings sliding against GCr15, ZrO2 and Si3N4 balls were comparatively investigated. The corrosion behaviors of both two coatings were also studied in 3.5% NaCl solution. The results show that the NiCrBSi-Zr coating (porosity of 0.6%) has a denser microstructure than the NiCrBSi coating (porosity of 2.3%). The interfaces in the NiCrBSi-Zr coating are free of oxide inclusions and cracks, presenting good inter-splat bonding. Owing to the improved inter-splat bonding, no friction and corrosion induced spalling was observed on the worn surface and corroded surface. The NiCrBSi-Zr coating exhibits better wear and corrosion resistance compared to the NiCrBSi coating.

Synergistic tribological behaviors of graphene oxide and nanodiamond as lubricating additives in water

Abstract There have been insistent demands for effective lubricants as well as additives for reducing friction and wear in various applications. Recently, graphene oxide (GO) and nanodiamond (ND) have been observed to be promising materials to reduce friction and wear in tribological studies. Herein, a novel lubricant has been developed by using GO and ND together as lubricant additives in water in order to enhance tribological performance. The tribopairs employed were Si3N4 balls and Si wafers, and the applied normal load was 5–80 mN. The lowest friction coefficient of approximately 0.03 was obtained for water with 0.1 wt.% GO and 0.5 wt.% ND, while the corresponding depth of wear track was as low as about 5 nm. Analysis of the tribological mechanisms elucidated that the sliding-induced nanostructured tribofilm, the low shearing resistance between graphene sheets, and the possible ball bearing effect of ND all contributed to the remarkable tribological behaviors of the lubricant.

Effects of temperature on the tribological behavior of Al0.25CoCrFeNi high-entropy alloy

The tribological behavior of Al0.25CoCrFeNi high-entropy alloy (HEA) sliding against Si3N4 ball was investigated from room temperature to 600 ℃. The microstructure of the alloys was characterized by simple FCC phase with 260 HV. Below 300 ℃, with increasing temperature, the wear rate increased due to high temperature softening. The wear rate remained stabilized above 300 ℃ due to the anti-wear effect of the oxidation film on the contact interface. The dominant wear mechanism of HEA changed from abrasive wear at room temperature to delamination wear at 200 ℃, then delamination wear and oxidative wear at 300 ℃ and became oxidative above 300 ℃. Moreover, the adhesive wear existed concomitantly below 300 ℃.

Friction and lubrication mechanism of a new type of anti-magnetic bearing Ti60 titanium alloy material

Abstract The tribological characteristics of Si3N4 ball sliding against a Ti60 disc lubricated by an as-synthesized ionic liquid (IL), perfluorooctane sulfonate phosphonium (L-4P), were studied using an oscillating reciprocating friction and wear tester at 50 and 150 °C. The scanning electron microscopy (SEM), friction test results by XRV-5, Energy Dispersive Spectrometer (EDS) and X-ray photoelectron spectroscopy (XPS) results show that the excellent tribological characteristics of Si3N4/Ti60 contacts lubricated by (L-4P) has excellent tribological characteristics. The friction surface of Ti60 against Si3N4 by lubricated with pentaerythritol ester (5750), diisooctyl sebacate (DIOS) and 1-butyl-3-methylimidazolium tetrafluoroborate (L-[BMIM][BF4]) are ploughing wearing, and the dominant wear mechanism are mainly abrasive particles wear, accompanying oxidation wear. As opposed to friction surface of L-4P is ploughing wearing with a lot of molten SnF2, and the dominant wear mechanism is mainly adhesive particles wear, accompanying abrasive wear and oxidation wear. A soft and low melting-point phase SnF2 generated due to chemical reaction between Ti60 and L-4P further lubricate the friction pairs, resulting in the best wear performance.

Effects of laser surface texturing on tribological properties of Ti-6Al-4V in hydroxyethyl-cellulose water-based lubrication

PurposeThis paper aims to investigate the effect of laser surface texturing on the tribological performance of Ti-6Al-4V disks sliding against Si3N4 balls under hydroxyethyl-cellulose water-based lubrication. The friction coefficients and wear losses of textured and untextured disks were measured and compared. The results indicate that the texture patterns can lead to reduction of friction and wear in the condition of water-based lubrication.Design/methodology/approachSolutions of hydroxyethyl cellulose were used as water-based lubricants. To find the optimal laser texturing parameters for the best performance enhancement, three line-like patterns were fabricated onto the disks and three machining parameters were used for each type of pattern. Tribological tests were conducted in rotation sliding with ball-on-disk contact configuration on UMT-2.FindingsA higher density of texture lines leads to a larger friction and wear reduction. Compared with untextured disks, the friction coefficient is reduced from 0.043 to 0.028 for textured disks. Some unworn parts were detected in the contact region of the balls against textured disks, which were not found on the balls against untextured disks. The worn surfaces indicated that periodic geometry of the contact track was rebuilt during run-in period, which was beneficial for the formation of lubricant films.Originality/valueIn this work, laser surface texturing was used to reduce the friction and wear of Ti-6Al-4V specimens in water-based lubrication, which can be used to improve the tribological performance of Ti-6Al-4V components in mechanical equipment.

Laser Additive Manufacturing of (Ti-6Al-4V)/10 wt.% Ag Composite Using Spherical Powders to Reduce Wear and Friction

In order to extend the service lifetime of Ti-6Al-4V-based components, friction and wear behaviors of Ti-6Al-4V alloys needed to be further improved. Laser additive manufacturing with a moving laser beam was used to prepare (Ti-6Al-4V)/10 wt.% Ag samples, on a three-dimensional RC-SLM400 printer with laser powers of 2-10 kW. (Ti-6Al-4V)/10 wt.% Ag samples were successfully printed using spherical powders prepared by gas atomization process (SPGAP) and combustion reaction (SP-CR). The tribological properties of the as-prepared samples sliding against Si3N4 balls were examined using a ball-on-disk tribometer. The results showed that the tribological behavior of (Ti-6Al-4V)/10 wt.% Ag printed by SP-CR was better than that of the sample printed by SPGAP. The low friction and reduced wear were mainly attributed to the formation of the lubrication layer containing large amounts of silver, which can exhibit an excellent deformation and plastic ductility. It effectively reduced the friction resistance and material loss and provided the good lubrication for 0-80 min, resulting in low friction and reduced wear of the samples prepared by SP-CR.

The synergistic lubricating mechanism of Sn-Ag-Cu and C60 on the worn surface of M50 self-lubricating material at elevated loads

The potential tribological properties of load-adaptive M50-based self-lubricating composites under various loads were investigated. Pure M50 and M50 composite containing 10 wt%(50Sn40Ag10Cu) (MSAC) samples were prepared by spark plasma sintering. Besides, samples M50 and MSAC, which were all surface-scattered with C60 microparticles, were defined as M-C and MSAC-C, respectively, and the tribological tests of M50, MSAC, M-C, and MSAC-C sliding against Si3N4 ball from 2 to 18N at 0.2 m/s-350 °C were performed. Results show that MSAC-C exhibits the excellent friction and wear performance within the range of loads. Analysis indicates that this phenomenon is mainly due to the formation of a composite lubricating film rich in soft metal lubricant Sn-Ag-Cu and C60 microparticles.

Microstructure, mechanical and tribological property of multi-components synergistic self-lubricating NiCoCrAl matrix composite

Abstract A multi-component synergistic self-lubricating NiCoCrAl matrix composite was fabricated by high-energy ball milling and spark plasma sintering. The composite exhibited excellent work hardening capability and mechanical properties which mainly attributed to the optimized microstructure and high content of hard reinforced phases. The outstanding self-lubricating property was deriving from the multiple-components synergistic lubricant including Ag, MoS2, LaF3 and CeF3 at room temperature. A continuous smooth tribofilm consisting of various silver molybdates and metallic oxide prevented the direct contact between the Si3N4 ball and the composite resulting in significantly decrease the friction coefficient and wear rate at 800 °C. However, the solid lubrication generated oxidation deterioration without the lubricating effect causing the relative serious worn damage at 400 °C.

Frictional properties of silver over-coated on surface textured tantalum interlayer at elevated temperatures

Surface textured tantalum interlayer is designed to improve the friction properties of silver at elevated temperatures. In this study, the textured dimples were fabricated on the tantalum coated steel by pulse laser and the Ag coatings were deposited on the textured Ta interlayer by DC magnetron sputtering. The friction properties of silver films on the textured tantalum interlayer were tested by rubbing against a Si3N4 ball on a ball-on-disk tribometer from 25 °C to 600 °C. The results show that the friction performance of silver at 200 °C, 400 °C, 600 °C is improved by the textured tantalum interlayer while the role of texture is not significant for friction reduction at room temperature. It is not found a consistent trend that point to the ability of texturing to reduce friction at elevated temperatures. At the temperature above 400 °C, the role of lubricant storage for texture is more dominant. The silver films deposited on the textured tantalum interlayer with the dimple density of 6% shows relatively stable and low friction coefficient (μ = 0.2) at 600 °C. The combination of Ta2O5 and silver clusters on the worn surface of Ag/textured Ta composite coating contributes to the low friction coefficient at elevated temperatures.

Effect of aluminizing and austempering processes on structural, mechanical and wear properties of a SSF ductile iron

The aim of this study is to investigate the effect of aluminizing process on structural, mechanical and tribological properties of GJS 600-10 solution strengthened ferritic (SSF) ductile iron before and after austempering heat treatment. The as-cast samples were coated by hot-dip aluminizing (HDA) at 750 °C for 5 min. For austempering heat treatment, the as-cast and aluminized samples were austenitized at 975 °C for 2 h and austempered (ADI) at 330 °C for 1 h, which were referred as ADI and HDA + ADI samples, respectively. Structural characterizations made by scanning electron microscopy (SEM), energy dispersive x-ray spectrometry (EDX) and x-ray diffraction (XRD) analysis revealed that single HDA process produced a coating of FeAl3 and Fe2Al5 layers with an Al topcoat on the surface. By the application of austempering after HDA, as-aluminized coating layer transformed into Fe2Al5 + FeAl2, FeAl and α-Fe with Al2O3 scale on the surface. Tensile tests conducted at room temperature indicated that single HDA does not significantly affect the mechanical properties of the as-cast ductile irons, whereas application of austempering after HDA decreases strength and increases ductility in comparison to ADI samples. Dry sliding wear tests performed against Si3N4 ball at room temperature showed that HDA samples exhibited much worse wear resistance than the as-cast samples. However, wear resistance was increased about 30% when austempering is applied after HDA. Formation of various oxides on the worn surfaces of the samples was studied by Raman spectroscopy and EDX analysis. Test results were comparatively evaluated on the basis of surface and subsurface characteristics of the investigated ductile irons, and showed that increased wear resistance can be obtained when HDA is followed by austempering for the ductile iron used in this investigation.

A New Asperity-Scale Mechanistic Model of Tribocorrosive Wear: Synergistic Effects of Mechanical Wear and Corrosion

A corrosive wear model is considered at the asperity-scale of a tribocorrosive wear system as well as the traditional Archard-type mechanical wear model. The geometry of the surface asperities is modified in a contact mechanics model with respect to both corrosive and mechanical wear calculations. This model was presented and validated for prediction of the electrochemistry in the first part of this work. The material used in the experimental part of this work was CoCrMo plate working electrode (WE) and Si3N4 ball as the counter body in a reciprocating configuration. Experiments were conducted at loads of 5, 7.5, and 10 N and the contributions of total mechanical wear and corrosion were measured. The model is then tuned to predict the chemical and mechanical components of the total wear of the system. The synergistic effect of corrosion on mechanical wear and mechanical wear on corrosion are modeled numerically in this work. The values are then used to explain different components of mechanistic tribocorrosive wear models present in the literature. This deterministic model, for the first time, calculates the corrosion-enhanced wear in a tribocorrosive wear environment and proposes that changes in the topography are responsible for this synergistic effect. The results show a linear dependence of the corrosion enhanced wear, wear-enhanced corrosion, and the pure mechanical wear on the applied load. Results also suggest that the wear enhanced corrosion has a significant contribution in the overall degradation of the material.

The analysis of the self-lubricating behavior and local failure mechanism of silver-rich solid film

PurposeThe main aim of this paper was to study the self-lubricating behavior and failure mechanism of silver-rich solid film for in-depth analyzing of the friction and wear property of TiAl-10 wt. per cent Ag self-lubricating composite.Design/methodology/approachThe friction and wear property of TiAl-10 wt. per cent Ag self-lubricating composite sliding against Si3N4 ball was tested under the testing conditions of ball-on-disk wear system. Field emission scanning electron microscopy and electron probe microanalyzer were used to analyze the surface morphology of silver-rich solid film. The main element contents were tested by energy dispersive spectroscopy. Silver phase on wear scar could be well identified using X-ray photo-electron spectroscopy. The theory calculation of shearing stress on wear scar was executed to discuss the local failure mechanism of silver-rich solid film. The lubricating role of silver was also discussed to analyze the anti-friction and anti-wear behavior of silver-rich solid film.FindingsThe friction coefficients and wear rates of TASC gradually reduced at 0-65 min, and approached to small values (0.31 in friction coefficient and 3.10×104 mm3N-1m-1 in wear rate) at 65-75 min. The excellent friction and wear behavior of TASC was mainly attributed to the lubricating property of silver-rich film at 65-75 min. At 12→20 N, surface shearing stress increased up to 146.31 MPa, and exceeded more than the shearing strength (125 MPa) of silver-rich film, which caused the propagating of fatigue crack and the destroying of silver-rich film, leading to high friction and severe wear.Originality/valueIt is important that the self-lubricating behavior and local failure of solid film is explored for further understanding the friction and wear property of TiAl alloys.