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Vera E.E.,Polytechnic University of Pachuca | Vite M.,Tribology Group | Lewis R.,University of Sheffield | Gallardo E.A.,Tribology Group | Laguna-Camacho J.R.,University of Veracruz
Wear | Year: 2011

In this study, the performance of the coatings TiN, CrN and WC/C applied on steel substrates that were subjected to sliding wear was analyzed. These materials normally exhibit an efficient performance in applications such as coatings of cutting tools, stamping processes, forming and plastic injection tooling where the contact and sliding conditions are severe. Due to this fact, this research was conducted to characterize the materials in relation to the wear process. The sliding wear test was performed using a reciprocating wear test machine. All tests were conducted in dry conditions with a room temperature between 20. °C and 23. °C and 45% to 50% relative humidity. A sliding velocity of 0.08 m/s and 2 mm amplitude were used. The applied loads were 11.76. N (Po = 1.74. GPa) and 7.84. N (1.52. GPa), respectively. Optical microscopy and scanning electron microscopy (SEM) were used to observe and analyze the wear mechanisms. Additionally, the variation of the friction coefficient versus the number of cycles was obtained. This was used to determine with a higher precision the time (presented as number of cycles) where the coating presented the initial signs of wear damage. In addition, energy dispersive X-ray analysis (EDS) was performed to obtain the chemical composition of the materials and hardness tests on the wear tracks were also carried out. It was possible to know the wear life of these coatings and possible causes of life variations. The load was an important factor in the variation of the wear life results, although other factors such as surface roughness and coating thickness were also significant. © 2011 Elsevier B.V.


Laguna-Camacho J.R.,University of Veracruz | Lewis R.,University of Sheffield | Vite-Torres M.,Tribology Group
Wear | Year: 2013

In this study, cavitation erosion tests were conducted on different materials such as pure aluminium (99% aluminium) and 1045 steel which were used as "vibratory" specimens, whereas untreated 6082 aluminium alloy, 304 stainless steel and 4340 steel were used as "stationary" specimens. A first set of tests was conducted using only tap water where a lower wear rate was observed. On the other hand, a second set of tests was carried out adding silicon carbide particles to the tap water which led to increase of the erosion wear rate. It helped to evaluate the performance of all the tested materials at different testing conditions.High speed camera was used to analyse the bubble formation in the radiating surface of the horn made of 2024 aluminium alloy. In these videos, it was possible to observe that the bubble formation was similar to the cone-like bubble structure (CBS) observed in other cavitation studies. Additionally, high speed videos were obtained as abrasive particles were used to conduct the tests. In these, it was possible to observe how abrasive particles were moving along the two surfaces, staying in the clearance to cause higher wear damage on both surfaces. The "stationary" specimen was located at a 1. mm distance with respect to the position of the "vibratory" specimen which was attached to the radiating surface. Optical microscopy was used to identify the wear mechanisms which were characterized by a pitting action when only tap water was used whereas some scratches and irregular indentations similar to those observed in abrasive wear were seen on the surfaces with abrasive particles. © 2012 Elsevier B.V.


Laguna-Camacho J.R.,University of Veracruz | Marquina-Chavez A.,University of Veracruz | Vite-Torres M.,Tribology Group | Gallardo-Hernandez E.A.,Tribology Group
Wear | Year: 2013

In this study, solid particle erosion tests were carried out to evaluate the performance of AISI 304, 316 and 420 stainless steels in relation to this wear process. These materials have several industrial applications such as turbine blades, valves, hard tools, fasteners, piping, storage tanks, water components, food processing equipment, etc. An erosion test rig similar to that shown in ASTM G76-95 standard was used to perform the tests. The abrasive particle used was angular silicon carbide (SiC) with a particle size of 420-450. μm. Tests were carried out using different impact angles (30°, 45°, 60° and 90°) with a particle velocity of 24±2. m/s and an abrasive flow rate of 150±0.5. g/min. The room temperature during the tests was between 35. °C to 40. °C. The chemical composition of the tested materials was obtained by using energy dispersive X-ray analysis (EDS). In addition, SEM images were used to identify the wear mechanisms. In this particular case, wear damage similar to brittle fracture with the detachment of large fragments was observed on the surfaces of AISI 304 and 316 stainless steels. Plastic deformation characterised by pitting and cutting action was also observed. In respect to AISI 420, it was only damaged by plastic deformation, with pitting and ploughing action, some random scratches and irregular indentations on its surface for all impact angles. The results showed that AISI 304 and 316 presented a higher erosion rate at 60°, whereas AISI 420 exhibited the higher erosion damage at 30°. Finally, Atomic Force Microscopy (AFM) was used to compare the roughness of the surfaces before and after the tests at 30° and 90°, respectively. © 2013 Elsevier B.V.


De Laurentis N.,Tribology Group | Kadiric A.,Tribology Group | Lugt P.,SKF Corporation | Cann P.,Tribology Group
Tribology International | Year: 2016

This paper presents new results examining the relationship between bearing grease composition and rolling-sliding friction in lubricated contacts. Friction coefficient and lubricating film thickness of a series of commercially available bearing greases and their bled oils were measured in laboratory tribometers. Test greases were selected to cover a wide spectrum of thickener and base oil types, and base oil viscosities. The trends in measured friction coefficients were analysed in relation to grease composition in an attempt to establish the relative influence of individual grease components on friction. Two distinct operating regions with markedly different friction behaviour are identified for each grease. At relatively high speeds the greases behave approximately as their bled/base oils, while in the low speed region the frictional response is very dependent on their thickener type and properties of the lubricating film. Low viscosity, synthetic base oil seems to offer efficiency advantages in the high speed region regardless of thickener used, while the choice of thickener type is significant under low speed conditions. © 2015 The Authors.


Laguna-Camacho J.R.,University of Veracruz | Cruz-Mendoza L.A.,University of Veracruz | Anzelmetti-Zaragoza J.C.,University of Veracruz | Marquina-Chavez A.,University of Veracruz | And 2 more authors.
Progress in Organic Coatings | Year: 2012

In this study, the performance of coatings that were subjected to solid particle erosion tests was evaluated. These coatings can be used to protect die casting molds. The main interest of this research project was to find possible alternatives to increase the wear resistance of these mechanical components. Die casting is a metal casting process that is characterized by forcing molten metal under high pressure into a mold cavity, which is machined into two hardened tool steel or coated dies. Most die castings are made from non-ferrous metals, such as aluminium, copper, magnesium, lead, zinc, tin based alloys but also they can be protected by specific coatings that have high wear resistance. The erosive wear damage in die casting molds is caused due to the molten metal is blown into the mold by high pressure dry air. Filling the mold cavities during the blown step, molten metal and sand particles impact the internal surface producing erosive wear damage. Coatings such as chromium nitride (CrN) and titanium aluminium nitride (TiAlN) that exhibit low wear damage in these types of applications due to high abrasion and erosion resistance were tested. In addition, uncoated 4140 steel and 6061 aluminium were also tested. An erosion test rig similar to that shown in ASTM G76-95 standard was designed and built to perform the tests. The abrasive particle used was angular silicon carbide (SiC) with a particle size of 420-450 μm. Tests were carried out using different impact angles (30°, 45°, 60°and 90°) with a particle velocity of 24 ± 2 m/s and an abrasive flow rate of 0.7 ± 0.5 g/min. The particle velocity and the abrasive flow rate were low in all of the tests to reduce the interaction between the incident particles and the rebounding particles in the system. The surfaces were examined with a scanning electron microscope (SEM) to characterize the erosive damage. The wear mechanisms identified were pitting and ploughing action at low impact angles (α ≤ 45°) due to sliding component commonly observed at these incident angles whereas bigger craters, radial cracks and a more roughened surfaces were seen at angles near or at 90°.In addition, it was observed that the damaged area was extended in all of the cases at 30°and 45°reducing considerably at 60°and 90°. The wear scars were characterized by an elliptical shape at 30°and 45°, which is a characteristic feature when the specimens are impacted at low-incident angles (α ≤ 45°) whereas a roughly circular was seen at 60°and 90°. © 2011 Elsevier B.V.


Vite J.,Centro Nuclear | Vite M.,Tribology Group | Castillo M.,Tribology Group | Laguna-Camacho J.R.,University of Veracruz | And 2 more authors.
Tribology International | Year: 2010

In this study, the performance of ceramic materials that were subjected to solid particle erosion was analyzed. This research was performed to characterize the materials in relation to the wear process. The materials could be used in the construction of devices and machine components that are commonly exposed to environments where volatile, abrasive particles typically cause a high rate of wear. The types of composites used in this study could have useful applications in mechanical components, automotive coatings, etc. These materials are usually obtained from solid residuals and volcanic ashes, in which clay and epoxy resin were used as binders. The erosion testing was performed in accordance with the ASTM G76-95 standard. The samples had a rectangular shape, and their dimensions were 50×25 mm2 and 10 mm in thickness. The abrasive particles used were angular silicon carbide (SiC) with a particle size of 420450 μm. The tests were performed using three different incident angles (30°, 45° and 90°) with a particle velocity of 24±2 m/s. The abrasive flow rate was 70 g/min. The particle velocity and the abrasive flow rate were low in all the tests to reduce the interaction between the incident particles and the rebounding particles in the system. Additionally, the total time of each test was 10 min, and the specimens were removed every 2 min to determine the amount of mass lost. The test specimens were located a distance of 7 mm from the shot blast. The surface of the specimens was examined with a scanning electron microscope (SEM), which characterized the erosive wear damage. The results indicated that all of the ceramic materials reached their maximum erosion rate at an incident angle of 90°. The erosion rate was significantly decreased when the angle of incidence was 30°. Additionally, the ceramics that consisted of volcanic ashes and sand mixed with epoxy resin gave a better erosion resistance compared with the materials that were combined with clay. It was assumed that the combination that was mixed with epoxy resin produced a more compact structure in the specimens, which resulted in a less severe attack of the particles that were acting on the surface of the material. The sand and the volcanic ashes that were mixed with clay, which had the poorest performance in the tests, exhibited similar behavior. It was also observed that the damaged area was extended in all of the cases that used an incident angle of 45°, whereas the depth of the wear scars was higher when an incident angle of 90° (normal incidence) was used. The wear scars were characterized by an elliptical shape at 30° and 45°, which is a characteristic feature when the specimens are impacted at low-impact angles (α≤45°), whereas a circular shape was observed at 90°. © 2010 ElsevierLtd. All rights reserved.


Vite M.,Tribology Group | Moreno-Rios M.,Tribology Group | Hernandez E.A.G.,Tribology Group | Laguna-Camacho J.R.,Tribology Group | Laguna-Camacho J.R.,University of Veracruz
Wear | Year: 2011

In this study, the abrasive wear resistance of AISI 316 and AISI H13 steels, uncoated and coated with sputtered CrN coating was evaluated by using an abrasive rubber wheel tester. The characterization process of the coatings was performed by using SEM, XRD and EDS techniques. Additionally, hardness tests were carried out with a Vickers microhardness tester. The substrates of AISI 316 and AISI H13 steels were manufactured as follows 25.4. mm. ×. 57.2. mm and 6.35 mm in thickness. The coating thickness for all samples was 4. μm. Coatings were deposited using a cathodic erosive equipment (DC Magnetron Sputtering). Angular abrasive steel particles (G80) were used to conduct the tests. The particle size was 200. μm and the particle hardness 450-480. HV. A nominal sliding speed of 200 rpm and a total sliding distance of 6000 m were used to run the tests. Also, a 64. N load was applied. The lost weight was monitored constantly every 1000 m. In addition, wear rates (Q) and wear coefficients (k) were obtained. The wear mechanisms identified were irregular indentations with plastic deformation and "galling" due to the shape and hardness of the steel particles. Additionally, three body abrasive wear was also present for both materials and typical wear damage such as cutting and plowing action, grooves, and parallel scratches. Finally, it was concluded that AISI H13 coated with the CrN coating exhibited the highest wear resistance compared to AISI H13 uncoated and AISI 316 steel coated and uncoated. © 2011 Elsevier B.V.


Vite-Torres M.,Tribology Group | Vite J.,Centro Nuclear | Laguna-Camacho J.R.,Tribology Group | Laguna-Camacho J.R.,Centro Nuclear | And 3 more authors.
Wear | Year: 2011

In this study, the performance of new ceramic materials that were subjected to dry abrasive wear was analyzed. This research was conducted to know the behaviour of these materials in relation to the wear process. The types of composites used in this study could have useful applications such as coatings to protect mechanical components, including engine pistons and steam generators. These new materials are usually obtained from solid residuals coming from mines. These are known as "jales" (náhualt derivated from xalli, it means sand). The abrasion testing was performed in accordance with ASTM G65-94 standard. Wear rates (Q) and wear coefficients (k) were also obtained. The surface of the specimens was examined with a scanning electron microscope (SEM). The wear mechanisms observed commonly on the specimens were parallel deep grooves and ploughing and cutting action. The results indicated that the ceramics that consisted of volcanic ashes and sand mixed with clay exhibited a higher abrasion resistance compared with the materials that were combined with epoxy resin. © 2011 Elsevier B.V.


Spikes H.,Tribology Group
Tribology Letters | Year: 2015

The need for energy efficiency is leading to the growing use of additives that reduce friction in thin film boundary and mixed lubrication conditions. Several classes of such friction modifier additive exist, the main ones being organic friction modifiers, functionalised polymers, soluble organo-molybdenum additives and dispersed nanoparticles. All work in different ways. This paper reviews these four main types of lubricant friction modifier additive and outlines their history, research and the mechanisms by which they are currently believed to function. Aspects of their behaviour that are still not yet fully understood are highlighted. © 2015 Springer Science+Business Media New York.


Stoncius A.,Tribology Group | Liascukiene I.,Tribology Group | Jankauskas S.,Tribology Group | Asadauskas S.J.,Tribology Group
Industrial Lubrication and Tribology | Year: 2013

Purpose - Workmanship concerns lead to more focus on volatile materials, released by industrial lubricants. Typically, flash point test and thermo-gravimetrical analysis (TGA) are used to investigate basestock volatility, but they do not address long-term decomposition tendencies of lubricants. The extent of volatile losses due to chemical degradation (oxidation, hydrolysis, dissociation, etc.) remains unclear. Design/methodology/approach - Vaporisation tendencies of eight additive-free bio-based, synthetic and mineral basestocks with similar viscosities were compared experimentally in a 30-80 h degradation test. Thin films (30-50 μm) of oils were placed on the steel surface and heated to 130-140 C with periodic cooling to room temperatures for gravimetric measurement of volatile losses. Findings - Mineral oils lost some fractions initially, but their evaporation subsided afterwards. To the contrary, PAO, polyglycol and polyol ester type oils showed low losses early into the test, but later they started producing high amounts of volatiles. After approx. 10-15 h the evaporation from mineral oils was clearly lower than that from synthetic or bio-based oils with substantially higher flash points. Originality/value - Test results challenge the existing viewpoint that viscous oils with high flash points are non-volatile. It was found that even fully synthetic and bio-based oils lost more than 30 wt.% contents, despite being considered almost non-volatile. Such extensive decomposition of oil films should be taken into account when making the equipment-engineering or workmanship-related decisions in the industry. © Emerald Group Publishing Limited.

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