High-temperature Wear Tester Research Articles

Computational and experimental prediction of dust production in pebble bed reactors, Part II

This paper is the continuation of Part I, which describes the high temperature and high pressure helium environment wear tests of graphite–graphite in frictional contact. In the present work, it has been attempted to simulate a Pebble Bed Reactor core environment as compared to Part I. The experimental apparatus, which is a custom-designed tribometer, is capable of performing wear tests at PBR relevant higher temperatures and pressures under a helium environment. This environment facilitates prediction of wear mass loss of graphite as dust particulates from the pebble bed. The experimental results of high temperature helium environment are used to anticipate the amount of wear mass produced in a pebble bed nuclear reactor.

Dry sliding wear behavior of PVD TiN, Ti55Al45N, and Ti35Al65N coatings at temperatures up to 600 °C

Three PVD nitride coatings (TiN, Ti55Al45N, and Ti35Al65N) with different Al content were deposited on the cemented carbides by cathode arc-evaporation technique. Microstructural and fundamental properties of these nitride coatings were examined. The friction and wear behavior of these coatings were evaluated at temperatures up to 600°C. The wear surface features of the test samples were examined by scanning electron microscopy. Results showed that the friction coefficient of these nitride coatings is different depending on the temperature. The friction coefficient of TiN coating increased with the increase of test temperature; while the friction coefficient of Ti55Al45N and Ti35Al65N coatings with the addition of Al decreased with the increase of test temperature. The Ti55Al45N and Ti35Al65N coatings exhibited higher wear resistance over the one without Al (TiN coating). The wear resistance of these nitride coatings at high temperature wear tests is significantly dependent on their tribological oxidation behavior. The Ti55Al45N and Ti35Al65N coatings with the addition of Al exhibited improved wear resistance as compared to the TiN coating, which was attributed to that their tribo-chemically formed Al2O3 exhibited better tribological properties than the TiO2 of the latter.

Load Effect on 1Cr18Ni9 Stainless Steel Wires’ Fretting Behaviors in Metal Rubber Dampers

Cool-drawn 1Cr18Ni9 stainless steel wires of  0.1~0.5 mm can be woven and punched to prepare metal rubber (MR) dampers. There is certain amount of contact point/surface on wires in the transformable component and the displacements between wires are at micron levels. This kind of dampers usually works at variable load. In order to study load effect on wires’ fretting behaviors i.e. MR components’ vibration fatigue behaviors, the two  0.3 mm wires are fixed in 0.1 mm-deep grooves cutting on the traditional column-block samples and dry fretting experiments at load of 20N, 25N and 30N are made on SRV high temperature wear tester. Experiments showed that wear course of ‘fretting cell’ could be plotted as four phases: polish, adherence, forming of the third bed and stabilization. Based on data of MR vibration fatigue experiment and reference report, parameters of fretting experiment are designed and friction coefficients are collected at load of 20N, 25N and 30N. Results indicate that friction coefficient rises at the beginning of fretting and it will reach the stable phase at point of 350, 240 and 120 fretting cycles respectively. In wire’s stabilization wear phase the value of friction coefficient fluctuate around 0.4-0.42 and the amplitude is below 0.1. Friction coefficient curves at the three degree of load are close to each other. Fretting traces are measured and studied by OLYMPUS LEXT OLS3000, laser scanning confocal microscope (LSCM), and KEYENCE VHX-600, three-dimensional microscopy. This paper compares the load effect on wires’ fretting behaviors and supply data support for MR materials’ application as dampers.

Friction and wear properties of hot-pressed NiCr–BaCr2O4 high temperature self-lubricating composites

In recent years, the increasing potential for the use of high temperature self-lubricating composites as sliding components at extreme environments have attracted great attention on these materials. In the present work, NiCr–BaCr2O4 self-lubricating composites have been prepared using the hot pressing method. The friction and wear properties of NiCr–BaCr2O4 composites were investigated by using a ball-on-disk friction and wear tester in sliding against alumina ball up to 800°C. At room temperature, the NiCr–20BaCr2O4 composite has a friction coefficient of 0.72, which is clearly higher than that (0.44) of NiCr alloy. However, the composites incorporated with BaCr2O4 exhibit distinct improvements in effectively reducing friction and wear in a temperature range of 400–800°C as contrasted with unmodified NiCr alloy. At 800°C, the NiCr–20BaCr2O4 composite exhibits a friction coefficient of 0.27 and a wear rate of 4.5×10–6mm3/(Nm), while the unmodified NiCr alloy has a friction coefficient of 0.41 and a wear rate of 9.2×10–5mm3/(Nm), respectively. At elevated temperatures, a dense and protective oxide glaze layer is generated on the worn surface of composites. The glaze layer was then investigated by means of scanning electron microscopy, laser Raman spectroscopy and nano-indentation. Tribo-oxidation reaction of BaCr2O4 during high temperature wear tests is responsible for the formation of the protective glaze layer. The newly formed BaCrO4 contains lubricious hexavalent-Cr6+, which can promote the densification of oxide glaze layer, and finally generate a dense lubricating film to effectively reduce friction and wear at elevated temperatures.

Friction and Wear Characteristics of BaCr2O4 Ceramics at Elevated Temperatures in Sliding Against Sintered Alumina Ball

In this article, friction and wear characteristics of BaCr2O4 ceramics have been investigated using a high-temperature friction and wear tester from room temperature to 800 °C in dry sliding against sintered alumina ball. At room temperature, the friction coefficient and wear rate of BaCr2O4 ceramics are quite high. BaCr2O4 ceramics exhibit low friction coefficients and small wear rates with temperature increasing up to 400–600 °C. The oxidation reaction of BaCr2O4 during high-temperature wear tests is responsible for the tribological properties. The oxidized product of BaCr2O4 is BaCrO4, which forms a smooth self-lubricating film on the worn surface to effectively reduce friction and wear. However, at 800 °C, severe oxidation reduces the relative density of sintered BaCr2O4 ceramics, and further expedites the materials removal process.

Effects of Al on Microstructure and High-Temperature Wear Properties of Austenitic Heat-Resistant Steel

Microstructure and high-temperature dry sliding wear at 600 °C in ambient air of austenitic heat-resistant steel ZG40Cr25Ni20 with different contents (mass percent) of Al (0 to 7. 10%) have been investigated. The results show that microstructures of 4. 68% and 7. 10% Al addition content consist of the matrix and reinforcement of inter-metallic compound γ' and carbide, while microstructures of ZG40Cr25Ni20 without Al and with Al of 1.68% are absent of γ'. Higher wear resistance than the original ZG40Cr25Ni20 alloy is achieved in alloys with higher content of Al under the same high-temperature wear test condition. The wear rates of Fe-25Cr-20Ni-7. 10Al and Fe-25Cr-20Ni-4. 68Al are only 20. 83% and 45. 83% of that of Fe-25Cr-20Ni, respectively. Heat-resistant steels with higher contents of Al (4. 72% and 7. 10%) have higher hardness than those with lower contents of Al (1. 68% and 0). Wear mechanisms of ZG40Cr25Ni20 are considered as severe plough plastic deformation and slight adhesive. However, wear mechanisms of Fe-25Cr-20Ni-4. 68Al are light micro-cutting and oxidation-wear, while that of Fe-25Cr-20Ni-7. 10Al are severe adhesive transfer and oxidation-wear.

Tribological Characterization and Wear Mechanisms of Novel Oxynitride PVD Coatings Designed for Applications at High Temperatures

In recent years, newly developed protective coatings for cutting tools have become more and more wear and abrasion resistant to the extreme environments associated with modern machining processes. On these new coatings the common pin on disk tribological tests have failed, resulting in practically no wear or strongly heterogeneous wear. For efficient tribological testing and determination of wear resistance of the new hard coatings it is therefore crucial to establish a valid set of room temperature and high-temperature wear test conditions. After a large number of preliminary tests performed on a state-of-the-art high-temperature pin on disc tester we identified optimized conditions for characterization of these new types of hard coatings. The investigated coatings comprised AlTiN-based reference, nanostructured Al-Cr-based nitride, oxynitride and oxide coatings deposited using an industrial rotating cathodes arc PVD process on cemented carbide. The nitrogen in the coating was progressively substituted by oxygen up to 100 at.% to create oxide structure in order to avoid oxidation of the coatings at high temperatures. These new oxide coatings are known to withstand extremely high temperatures in dry milling and turning of high-strength materials while exhibiting high wear resistance. However, characterization of their wear resistance by the common tribological tests had proven to be very difficult and new testing procedures had to be established.

Effect of Loads on the Wear Properties of La<sub>2</sub>O<sub>3</sub>-MoSi<sub>2</sub> Composite against SiC at Elevated Temperature

Wear behaviours of La2O3-MoSi2composite against SiC under different loads at 1000°C and 0.126m/s sliding speed in air were investigated by using an XP-5 type high temperature friction and wear tester. The worn surfaces and phase of the sample were observed by scanning election microscopy (SEM) and X-ray diffraction (XRD), respectively. Results showed that friction coefficient and wear rate of La2O3-MoSi2composite and SiC decreased with the increase of loads. The wear mechanisms of La2O3-MoSi2composite are oxidation, adhesion abrasion and fatigue pitting.

The Study of the Properties and Function of Large Ball Mill with Liner Material

In this paper, based on ctual large-scale ball mill liners working conditions, effects of different quenching temperature and tempering temperature on the Cr-Mo steel performance, optimize the best heat treatment process.The use of sophisticated electronic universal tensile testing machine, and Rockwell hardness testing machine for testing mechanical properties of steel materials were tested; Using the MMS-1G-type high-temperature high-speed Friction and wear tester, the wear properties of steel samples were studied using JSM-5610LV scanning electron microscope study of the tensile test fracture surfaces of steel and the friction and wear morphology. The results show that: For the high carbon alloy steel, of which 870 °C 620 °C tempered quenched specimen extension rate of 7.0% area reduction rate of 9.5%.

Tribological Behavior of Mesophase Carbon Added with Titanium and Copper

Incorporation of metallic elements, titanium and copper, into carbonaceous mesophase (CM) was performed through mechanical alloying in a ball mill apparatus. The structures of the raw CM as well as the Ti/Cu-added CM were characterized by X-ray diffraction. The tribological behavior of the Ti/Cu-added CM used as lubricating additives was investigated by using a high temperature friction and wear tester. The results show that, compared with the raw CM, the Ti/Cu-added CM exhibits a drop in the crystallinity and a transition to the amorphous. The Ti/Cu-added CM used as lubricating additive displays an obvious high temperature anti-friction and wear resistance effect, and the lager the applied load, the lower the friction coefficient and the wear severity.

Effect of Sliding Speed on Wear Property of MoSi<sub>2</sub> at High Temperature

Wear behaviors of MoSi2against Al2O3or SiC under 30N at 1000°C in air have been investigated by using an XP-5 type High Temperature Friction and Wear Tester. The worn surfaces and phases of samples were characterized by scanning electron microscope (SEM) and X-ray diffractometer, respectively. Result shows the wear rate and friction coefficient of MoSi2decreases with the increase of sliding speed. SiC is superior to Al2O3as the counter-face materials of MoSi2. Serious adhesion leads to very high wear rate of Al2O3in this experiment. SiC shows a surprising mass weighing phenomenon, which is caused by oxidation. The main wear mechanism of MoSi2against Al2O3is oxidation and adhesion. However when against SiC, it is chiefly controlled by grinding.

Effect of La 2O 3 on the wear behavior of MoSi 2 at high temperature

Wear behaviors of MoSi 2 doped with La 2O 3 against SiC under different loads at 1000 °C in air were investigated by using an XP-5 type high temperature friction and wear tester. The worn surfaces and phases of the samples were analyzed by scanning electron microscopy (SEM) and X-ray diffraction, respectively. Results showed that the addition of La 2O 3 could obviously improve wear resistance of MoSi 2. Because of the formation of MoO 3 phase on the worn surface, La 2O 3/MoSi 2 composite mainly exhibited oxidation and abrasive wear, which was different from the wear form of MoSi 2 such as adhesion, oxidation and abrasion.

Friction and wear of Synfluo 180XF wax and nano-SiO2 filled hybrid glass/PTFE fabric composites with phenolic resin binder

Hybrid glass/polytetrafluoroethylene (PTFE) fabric composites filled with micrometre Synfluo 180XF wax (SFW) and nano-SiO2 were prepared by dip coating of hybrid glass/PTFE fabric in phenolic adhesive resin containing the particles to be incorporated and successive curing. The friction and wear behaviours of these hybrid composites sliding against AISI-1045 steel in a pin on disc configuration were evaluated on a high temperature friction and wear tester. The composite structures and the morphologies of the worn surfaces were analysed by means of scanning electron microscopy. The results show that the addition of SFW and nano-SiO2 can improve the wear resistance and friction reduction in the hybrid composite, and the addition of nano-SiO2 endows the composite with best triboperformance. The improved triboperformance of nano-SiO2 or SFW filled hybrid glass/PTFE fabric composites can be attributed to the self-lubricating properties of filler, the improved structural stability and the special characteristics of transfer film.

Test research on sticking mechanism during hot rolling of SUS 430 ferritic stainless steel

The sticking phenomenon during hot rolling of SUS 430 ferritic stainless steel was investigated by means of a two-disc type high-temperature wear tester. The test results indicate that sticking particles on the surfaces of high chromium steel (HiCr) and high-speed steel (HSS) rolls undergo nucleation, growth, and saturation stages. Grooves on the roll surface generated by grinding provide nucleation sites for sticking particles. The number of sticking particles on the HiCr roll surface is greater than that on the HSS roll surface. The average surface roughnesses (Ra) of HiCr and HSS rolls change from 0.502 and 0.493 μm at the initial stage to 0.837 and 0.530 μm at the saturation stage, respectively. The test further proves that the sticking behavior is strongly dependent on roll materials, and the HSS roll is more beneficial to prevent particles sticking compared with the HiCr roll under the same hot-rolling conditions.

In situ Raman spectroscopy for examination of high temperature tribological processes

Abstract Raman spectroscopy of solid lubricant coatings during high temperature (300–700 °C) wear testing was employed for real-time correlation of sliding contact surface chemistry to the measured friction coefficient. Two coatings were investigated in this work – MoS2 and VN-Ag. Immediately prior to failure of the MoS2 coating at 350 °C, molybdenum trioxide was detected in the wear track, and an increase in friction coefficient and ultimate failure of the coating was associated with buildup of the abrasive oxide compound. For the VN-Ag nanocomposite coating, in situ Raman analysis of the contact surface during heating revealed the appearance of silver vanadate compounds at a temperature of 375 °C. At higher temperatures, competitive evolution of different silver vanadate phases (i.e., Ag3VO4, AgVO3) was observed. For the conditions examined in this work, the wear process at 700 °C inhibited formation of AgVO3 in the sliding contact, as determined by comparison of the composition of the wear track to that of the adjacent, unworn coating surface. Additionally, the composition of the wear track was significantly different after the sample had cooled sufficiently to allow handling for post-test surface characterization with conventional Raman, XRD, and SEM techniques, further illustrating the utility of in situ diagnostics for identification of active lubricant phases during wear tests. This ability to characterize surfaces during wear tests at elevated temperatures fills an important gap left by current in situ tribology techniques that are currently used to provide insight on mechanisms governing the performance of solid lubricant film materials.

Fabrication and tribological properties of HSS‐based self‐lubrication composites with an interpenetrating network

AbstractA new range of high‐speed steel (HSS)‐based self‐lubrication composites, with an interpenetrating network, were fabricated by infiltrating Pb‐Sn‐Ag ternary solid lubricants into TiC‐reinforced HSS pre‐forms. The microstructure and mechanical properties were investigated before and after infiltration. The tribological behaviour of the composites was investigated using a pin‐on‐disk, high temperature wear testing machine at different temperature (up to 800°C). Analysis indicated that Pb‐Sn‐Ag solid lubricants were well dispersed and embedded in the TiC‐HSS matrix where both solid lubricant phase and matrix phase interpenetrating throughout the microstructure. The friction coefficient and specific wear rate of the composites decreased with the increase of the volume fraction of Pb‐Sn‐Ag solid lubricants up to 15 vol%. With further increases in Pb‐Sn‐Ag volume fraction, the friction coefficient decreased slightly while the wear rate increased rapidly. The reason is that a large degradation of mechanical properties occurred in samples with high Pb‐Sn‐Ag contents. Copyright © 2010 John Wiley & Sons, Ltd.

Effects of Alloying Elements on Microstructure, Hardness, Wear Resistance, and Surface Roughness of Centrifugally Cast High-Speed Steel Rolls

A study was made of the effects of carbon, tungsten, molybdenum, and vanadium on the wear resistance and surface roughness of five high-speed steel (HSS) rolls manufactured by the centrifugal casting method. High-temperature wear tests were conducted on these rolls to experimentally simulate the wear process during hot rolling. The HSS rolls contained a large amount (up to 25 vol pct) of carbides, such as MC, M2C, and M7C3 carbides formed in the tempered martensite matrix. The matrix consisted mainly of tempered lath martensite when the carbon content in the matrix was small, and contained a considerable amount of tempered plate martensite when the carbon content increased. The high-temperature wear test results indicated that the wear resistance and surface roughness of the rolls were enhanced when the amount of hard MC carbides formed inside solidification cells increased and their distribution was homogeneous. The best wear resistance and surface roughness were obtained from a roll in which a large amount of MC carbides were homogeneously distributed in the tempered lath martensite matrix. The appropriate contents of the carbon equivalent, tungsten equivalent, and vanadium were 2.0 to 2.3, 9 to 10, and 5 to 6 pct, respectively.

HIGH TEMPERATURE TRIBOLOGICAL PROPERTIES OF SPARK-PLASMA-SINTERED Al2O3-SrSO4 SELF-LUBRICATING NANOCOMPOSITES INCORPORATED WITH AND WITHOUT Ag ADDITION

Spark plasma sintering (SPS) is employed to fabricate self-lubricating Al 2 O 3- SrSO 4 nanocomposites incorporated with and without Ag addition. The friction and wear properties have been evaluated using a high temperature friction and wear tester from room temperature to 600°C in dry sliding against alumina ball. X-ray diffraction (XRD), scanning electron microscopy (SEM) equipped with energy dispersive X-ray (EDX) analyzer were used to investigate microstructure and self-lubrication mechanisms of nanocomposites after wear tests at different temperatures. Al 2 O 3- SrSO 4 nanocomposites with optimum compositional combinations exhibit low and stable friction coefficients of 0.22 and wear rates in the order of 10-5 mm3/Nm at high temperatures. At low temperature, the Ag additives in the composite form a discontinuous lubricating film to effectively reduce friction and wear. With increasing test temperature, plastic deformation of SrSO 4 during sliding plays an important role in formation of lubricating films on worn surfaces to reduce the friction and wear.

Effects of Alloying Elements on Sticking Behavior Occurring during Hot Rolling of Modified Ferritic STS430J1L Stainless Steels

In this study, effects of alloying elements on the sticking behavior occurring during hot rolling of five kinds of modified ferritic STS430J1L stainless steels were investigated by analyzing high-temperature hardness and oxidation behavior. Hot-rolling simulation tests were conducted by a high-temperature wear tester that could simulate actual hot rolling. The simulation test results revealed that the sticking process proceeded with three stages, i.e., nucleation, growth, and saturation. Since the hardness continuously decreased as the test temperature increased while the formation of Fe-Cr oxides in the rolled steel surface region increased, the sticking of five steels was evaluated by considering both high-temperature hardness and oxidation. The addition of Zr, Cu, or Si had a beneficial effect on the sticking resistance, while the Ni addition did not make much difference to the sticking. Particularly, in the Si-rich steel, Si oxides formed first in the initial stage of the high-temperature oxidation, worked as initiation sites for Fe-Cr oxides, accelerated the formation of Fe-Cr oxides, and thus, decreased the sticking by over 10 times in comparison with the other steels.

High temperature friction and wear performances of Ti/Cu-doped carbonaceous mesophases

Incorporation of metallic elements Ti and Cu into the carbonaceous mesophase (CM) through mechanical alloying was performed in a high energy ball mill apparatus. The structures for the raw and Ti/Cu-doped carbonaceous mesophases were characterized by X-ray diffractiometer. The friction and wear behavior of the Ti/Cu-doped CMs as lubricating additives at different applied loads and temperatures were investigated using a MMU-5G high temperature friction and wear tester. Worn morphologies of the lower 45# steel specimens were observed by scanning electron microscope. The carbonaceous substances on the worn surfaces were examined by Raman spectroscopic technique. The results have shown that the Ti/Cu-doped CM through mechanical alloying shows a drop in the crystallinity in comparison to that for the raw CM, implying a transition to the amorphous structures. The Ti/Cu-doped CMs through mechanical alloying, when used as lubricating additives, displayed an obvious high temperature anti-friction and wear resistant effect, and the larger the applied load, the lower the friction coefficient and the wear severity. In addition, as the applied load increases, the carbonaceous substances on the worn surfaces show a rise in the ordered degree, and the corresponding microcrystalline planar size (La) for the carbonaceous substances becomes larger.