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In this work, Al2O3–ZrO2 nanocomposite ceramics were fabricated by spark plasma sintering (sps). The effects of nano-sized SiC and plasma treating technology on the tribological behavior were investigated. The experimental results showed that the grain size of ZrO2 changed from 250nm to 160nm with the addition of nano-SiC. The highest value of toughness, 6.0MPam1/2, was acquired in Al2O3–ZrO2–SiC...
The performance of a Cu–40Zn alloy during unidirectional and bidirectional (forth-and-back) sliding wear processes was investigated. It was observed that the alloy was worn less during bidirectional wear than during unidirectional wear. The mass loss of alloy decreased as the number of sliding-direction reversals was increased; correspondingly, hardness of the worn surface decreased after initial...
The fretting wear behavior of conventional and nanostructured Al 2 O 3 –13wt%TiO 2 coatings fabricated by plasma spray was studied in this paper. The conventional coatings were deposited with commercial Metco 130 feedstock, and the nanostructured coatings were deposited with agglomerated feedstock with nanostructure. There were typical lamellar structures existing in conventional...
The microstructure, hardness and erosion behavior of High velocity oxy-fuel (HVOF) thermal sprayed and heat treated NiAl intermetallic coatings with three different ceria were studied through erosion tests, Vickers hardness tests and microstructural characterizations in this paper. Test results showed that heat treatment can obviously change the erosion behavior of the HVOF thermal sprayed NiAl intermetallic...
Tribological and corrosion behaviors of nanostructured tungsten carbide (WC) particles/polymer composite coatings were studied by using microscratch technology and electrochemical technique. The coatings containing nanostructured WC particles showed a significant increase in hardness and scratch resistance compared to that of pure polymer coating. The improvement in hardness and scratch resistance...
This study reports the effect of CeO 2 on the erosion and abrasive wear properties of the HVOF thermal sprayed FeAl intermetallic coatings. It has been found that the FeAl intermetallic coatings containing CeO 2 are featured with fewer cracks, less porosity, and higher hardness than the pure FeAl coatings. The FeAl intermetallic coatings containing CeO 2 have exhibited significant...
Surface ring crack defects are normally found on the surfaces of ceramic balls. These ring cracks are circular extending for approximately one quarter of circumference of a circle and these cracks can significantly reduce rolling contact fatigue life. In this study, a boundary element analysis was carried out to identify the main factors governing the propagation of sub-surface cracks. The calculations...
Surface ring crack defects found on the surface of ceramic balls can reduce the rolling contact fatigue life (RCF) performance. In this study, various crack sizes were selected to identify the failure mechanisms in various lubricants. A modified four-ball machine was used to perform rolling contact fatigue testing. The crack within the contact path was carefully oriented and positioned the same way...
In this paper, the tribological and electrochemical corrosion properties of Al 2 O 3 /polymer nanocomposite coatings were studied by using micro-hardness test, single-pass scratch test, abrasive wear test, and finally electrochemical technique such as potentiodynamic polarization measurement. The coatings containing Al 2 O 3 nanoparticles showed improvement in scratch...
Piston skirt/cylinder bore scuffing is one of the main failure mechanisms that affect the life of automotive engines. The purpose of this research is to study hot scuffing and wear resistance of piston skirts with different surface textures and coatings running against cylinder bores using an apparatus which can simulate the relative motion between the piston and cylinder bore. The experimental studies...
Surface defects such as ring cracks are located on silicon nitride ceramic rolling elements. The random nature of ring crack position creates difficulties in predicting rolling contact fatigue (RCF) life. The influence of the lubricant on the RCF mechanism is difficult to determine due to the scattered nature of RCF life. In this study, a novel experimental technology was utilised to perform rolling...
The properties of ceramics, specifically low density and high stiffness are of most interest to gas turbine and machine tool manufacturers. High hardness, low coefficient of thermal expansion and high temperature capability are properties also suited to rolling element materials. Much research over the past two decades on its structure, quality control and manufacturing techniques has produced ceramic...
The mechanism of surface failure from a pre-existing line defect under rolling contact has been studied using a boundary element method. A three-dimensional boundary element model has been developed in order to investigate how the pre-existing defect affects the surface fracture behaviour and to determine the geometry of acceptable line defects. Research shows that the pre-existing line defects significantly...
This investigation reports the effect of CeO 2 and Cr additives on the microstructures, micro-indentation and erosion properties of the high velocity oxy-fuel (HVOF) thermal sprayed NiAl intermetallic coatings. It has been found that the addition of CeO 2 and Cr reduces the tendency of brittle peeling of NiAl intermetallic coatings during thermal spraying, presumably due to the improved...
Observations of failure mechanisms of silicon nitride rolling elements in relation to surface line defects under rolling contact has been carried out. The purpose of the present investigation is to study the way in which surface line defects fatigue fails and to interpret the failure processes. The rolling contact tests are performed on silicon nitride/steel elements. A modified four-ball machine...
Novel aluminium alloy matrix composites reinforced by 15vol.% Ni 3 Al intermetallic particles were prepared by a powder metallurgy route. The 6092 aluminium alloy was produced by gas atomisation, followed by blending with Ni 3 Al particles. Consolidation by extrusion at 515°C, with an extrusion ratio of 30:1, produced a uniform distribution of Ni 3 Al in the Al alloy matrix...
Silicon nitride has been found to have the optimum combination of properties which are suitable for rolling element bearing applications to withstand high loads, severe environments, and high speeds. Surface ring cracks are difficult to detect but are found on the surface of silicon nitride balls. These ring crack defects decrease the rolling contact fatigue life considerably. This paper presents...
The influence of ring crack location within the contact path on rolling contact fatigue failure has been studied using numerical fracture analysis. The numerical calculations are based on a three-dimensional model for the ring crack propagation. The ring crack is considered as a conic shape with a curved line as the crack front. The rolling contact loading is simulated by repeated Hertzian point contact...
This paper presents an experimental study of the influences of ring crack location within the contact path on the rolling contact fatigue failure. The rolling contact tests are performed on silicon nitride/steel elements. Silicon nitride ball surfaces are examined before testing using a dye-penetrant technique and light microscopy. The surfaces during testing, post-test and after failure are examined...
The use of silicon nitride applied to rolling element bearings shows some practical advantages over traditional bearing steels. The contribution of this present study is to provide understanding of surface crack defect characteristics and the subsequent rolling fatigue modes of failure. Surface defects such as pressing faults and ring cracks are characterised using light microscopy. Experimental bench...
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