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Hardmetal coatings prepared by high velocity oxy-fuel (HVOF) spraying represent an advanced solution for surface protection against wear. In the current systematic study the high-temperature oxidation and unidirectional sliding wear in dry and lubricated conditions were studied. Results for a series of experiments on self-mated pairs in dry conditions as part of that work are described in this paper. Coatings with nominal compositions WC-10%Co4%Cr, WC-(W,Cr)2C-7%Ni, Cr3C2-25%NiCr, (Ti,Mo)(C,N)-29%Ni and (Ti,Mo)(C,N)-29%Co were prepared with an ethylene-fuelled DJH 2700 HVOF spray gun. Electrolytic hard chromium (EHC) coatings and bulk (Ti,Mo)(C,N)-15%NiMo (TM10) hardmetal specimens were studied for comparison. The wear behaviour was investigated at room temperature, 400 and 600 °C. For the coatings sliding speeds were varied in the range 0.1–1 m/s for a wear distance of 5000 m and a normal force of 10 N. In some cases the WC- and (Ti,Mo)(C,N)-based coatings showed total wear rates (sum of wear rates of the rotating and stationary samples) of less than 10?6 mm3/Nm, i.e., comparable to values typically measured under mixed/boundary conditions. Coefficients of friction above 0.4 were found for all test conditions. The P × V values as an engineering parameter for coating application are discussed. The microstructures and the sliding wear behaviour of the (Ti,Mo)(C,N)-based coatings and the (Ti,Mo)(C,N)-15%NiMo hardmetal are compared. 相似文献
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The friction and wear behaviour of self-mated couples of MgO---ZrO2, Al2O3 and two types of SiSiC were studied under dry sliding conditions in a special pin-on-disc high temperature tribometer. The temperature was varied between 25 and 1000°C, and the sliding speed from 0.03 m s−1 to 3 m s−1. The morphology of the worn surfaces was studied by means of SEM, and their phase distribution by X-ray diffraction and TEM analyses. The results show that the wear coefficients of all couples mostly increase with increasing temperature and sliding velocity. The wear of MgO---ZrO2 is influenced by tribo-induced phase transformations while α-Al2O3 retains its original structure for all test conditions. For SiSiC delamination and fatigue of the interface Si/ß-SiC predominate. At higher temperatures and sliding velocities tribo-oxidation is effective. The friction coefficients lie between 0.5 and 1.0 under steady-state conditions but for short test durations lower values can occur. The couple SiSiC/SiSiC has low friction coefficients at low sliding velocities and temperatures, even if the steady-state region is reached. 相似文献
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D. Spaltmann M. Lhr S. Binkowski N. Kelling R. Soltwedel M. Woydt E. Santner 《Materialwissenschaft und Werkstofftechnik》2005,36(2):62-68
Damages of slip‐rolling tested DLC coatings on steel substrates of different hardness Extremely hard diamond coatings on hard SSiC substrates, various hard DLC coatings on 100Cr6 substrates (HRC60) as well as selected DLC coatings on unhardened steel substrates (HRC20) were tested under slip‐rolling conditions. Unadditivated paraffin oil was used as a lubricant. The tests were carried out in an Amsler type twin disc tester at initial maximum pressures of P0=2.3 GPa according to Hertz. The tests were terminated after n=1.000.000 revolutions (endurance tests: n=10.000.000 revolutions) or if a coherent damaged area of A>1 mm2 occurred. The slip‐rolling tests showed that the SSiC had a supportive influence on the diamond coatings which, however, failed due to fractures in the substrate. At least two of the DLC coatings on 100Cr6 substrates (HRC60) withstood the slip‐rolling test for up to n=10.000.000 revolutions with nearly no visible damage. These coatings deposited onto a soft, nitrogen alloyed steel (HRC20) were able to adjust to the deformation of the substrate without major damaged areas (A>1 mm2). 相似文献
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The dilution of biogenic fuels into lubricating engine oils often leads to a shortening of the recommended oil drains (between 30% and 60%) and an increase in wear. The large number of overlapping and influencing factors, of which dilution and polymerization of fuel components in the engine oil are emphasised, makes it difficult to find a uniform solution to prevent failures in the various applications. Insofar single solutions for the different types of biofuels are needed. The contribution of base oil chemistry and additives as well as triboactive materials is featured to deal with the adverse effects of biofuels. In the frame of the European Commission (EC)‐funded project ‘cleanengine’, tentative engine oils based on esters with a content of renewables and polyglycols are formulated to increase the lubricant's tolerance in engines fuelled with biofuel‐based blends, with the aim of ensuring required lubricating and wear protection performance while keeping oil drain intervals unchanged. The present paper focuses on four‐stroke diesel applications, fuelled by biodiesel (fatty acid methyl ester — FAME) as well as by rapeseed oil and Jatropha oil (pure vegetable oils, triglycerides), together with relevant blends of those biofuels and conventional diesel fuel. This paper screens the functional profile (in particular rheological, toxicological, bio‐compatibility, tribological and biofuels affinity) of lube families with respect to biofuel contamination. Moreover, this is followed by the contributions of piston ring and liner materials as well as thin film coatings. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
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In hip replacement the wear rate is reduced when using femoral heads and acetabular cups made of alumina ceramics. It is proposed to use Y‐TZP zirconia ceramics. The process on the articulating surfaces head/cup are not totally understood, especially the temperature rise due to frictional heating. Alumina is a stable material, no problems are expected. When using Y‐TZP its phase transition may be triggered due to frictional heating and the leaching out of yttria. The model proposed by Blok, Jaeger and Kuhlmann‐Wilsdorf was used to calculate the flash temperature under in vivo conditions. The surface temperature of the wear couple Y‐TZP/Y‐TZP was higher than the one for alumina/alumina. 相似文献
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Validation of the Resistance of ZrO2‐Mini Balls against Hot Vapour Sterilisation Mini‐balls are used in bearings of dental drills. As the bearings as well as the drills are hot vapour sterilised, the bearings are operated under non‐lubricated conditions. In the present study, Raman scattering experiments show that hot vapour sterilisations of Y2O3 stabilised ZrO2‐Mini‐balls lead to a phase transition from tetragonal to monoclinic ZrO2. This phase transition finally causes the failure of ZrO2‐Mini‐balls under the tribological conditions typical for dental drills. If, however, the ZrO2‐Mini‐balls are stabilised using CeO2, such hot vapour sterilisation induced phase transitions could not be observed. Subsequent tribological experiments prove that CeO2 stabilised ZrO2‐Mini‐balls, produced in a Sol‐Gel process, are resistant to slip‐rolling conditions, if large pores can be avoided. 相似文献
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Characterization of the Tribological Behaviour of Ceramic Sliding Couples with Modern Surface Analysis Methods Dry friction and wear tests were performed in ambient atmosphere with various self-mated couples of SiC, Al2O3, Si3N4 and ZrO2. The temperature was varied between 22 °C and 1000 °C and the sliding velocity between 0.03 m/s and 5 m/s. Normal force, temperature and sliding velocity are kept constant during the tests. The materials and wear mechanisms were characterized by various surface analytic methods – optical microscopy, scanning electron microscopy, transmission electron microscopy, electron microprobe analysis, IR-spectroscopy, X-ray diffraction, auger electron spectroscopy and X-ray photoelectron spectroscopy. High wear/low wear transitions could be explained. On the basis of these results new ceramic materials with lower friction and/or wear were selected or successful developed. 相似文献