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Aromatic Thermosetting Polyester (ATSP)-based coatings exhibit extremely low wear rates (4.15×10-8mm3/Nm) under boundary lubrication simulating tilting pad bearings in harsh conditions. It is acknowledged that coatings’ resistance to abrasive particles encountered in the bearing is also critical; the abrasive wear resistance of ATSP-based coatings and polyether ether ketone(PEEK)-based coatings are...
Under extreme operating working conditions, the oil film in hydrodynamic bearings may get destroyed, resulting in mixed and boundary lubrication conditions; subsequently, the bearing surfaces might seize and cause catastrophic failure, rendering the machine non-operable. To address these extreme working conditions, three advanced coatings are proposed in this paper: polytetrafluoroethylene (PTFE)...
The implementation of carbon dioxide (CO 2 ) as an alternative refrigerant for air-conditioning compressors has gained significant attention recently. The main interest in CO 2 is related to its zero ozone depletion potential (ODP) and low global warming potential (GWP) compared to commonly used hydroflurocarbon (HFCs) refrigerants such as R-134a. Friction and wear studies on tribological...
Blended Polyetheretherketone (PEEK) and polyimide-based polymers are excellent lighter tribomaterials that make possible the replacement of sliding metallic components in machinery. In this work a quantitative analysis of the effect of surface roughness on the transfer of polymer films was investigated using a specialized tribometer, under air-conditioning and refrigeration specific operating conditions...
Micromechanical and microscratch properties of chemical vapor deposition synthesized hafnium diboride thin solid films were measured. A range of synthesis conditions was explored by varying the substrate temperature, precursor pressure, and ex situ annealing conditions. Adhesion and shear strength measurements were performed using indentation and scratch techniques, respectively. The hardness of the...
Concerted research efforts have been made in the field of alternative refrigerants due to environmental concerns. Newly developed, HFO-1234 yf (2,3,3,3-Tetrafluoropropene) refrigerant has been proposed as a direct replacement solution for substituting the existing harmful hydrofluocarbon refrigerants, such as R134a (1,1,1,2-Tetrafluoroethane). This paper presents a comparative tribological study of...
Due to favorable tribological performance, PTFE- and PEEK-based polymeric coatings have received interest in air-conditioning and refrigeration compressor applications, as a potential solution to supplement and potentially replace conventional oil lubricants. The literature in this area is somewhat scarce, especially on the tribological performance of PTFE- and PEEK-based polymeric coatings under...
This paper examines the effects of surface roughness and lubrication on the early stages of fretting response of aluminum and steel lap joint samples. Qualitative and quantitative changes in fretting loops due to changes in loading; roughness characteristics, and contact conditions are analyzed. Roughness is found to influence friction force, tangential joint stiffness, partial slip displacements,...
Rail steel with bainite microstructure was developed to further increase steel hardness for improved durability and wear. Even though bainitic steel has higher bulk hardness, it showed worse wear performance than pearlitic steel, which was attributed to the superior work hardening capabilities of conventional pearlitic steel under severe operating stress conditions. As the effects from the wheel/rail...
Railroads in the United States spend approximately $2.5 billion a year on rail replacement and repairs, making rail the most valuable asset for the railroad industry in North America. The Transportation Technology Centre, Inc. (TTCI) continuously conducts full-scale rail performance tests using the newest generations of premium rails. This in turn allows better understanding of the rail characteristics...
Environmental concerns have increased the interest in alternative natural refrigerants for air-conditioning and refrigeration compressors. Carbon dioxide (CO 2 ) or R744 is an attractive candidate to replace harmful hydrofluorocarbon refrigerants, which will need to be replaced in the near future due to their high global warming potential. In this paper the tribological behavior of gray cast...
In this paper, the effect of micro-structural parameters (eutectic carbides and matrix hardness) on the micro-abrasive wear of multi-component ferrous alloys abraded by soft, fine abrasive particles is analyzed. Two series of quenched and tempered alloys, with variable vanadium or molybdenum contents and fixed amounts of other elements, were tested. Each series includes an alloy free of carbides (matrix...
Carbon dioxide (CO 2 ) has received significant interest as an alternative refrigerant for air-conditioning compressors due to its environmental benefits. These environmental benefits include zero ozone depletion potential and minimal global warming potential compared to commonly used hydrochlorofluorocarbon and hydrofluorocarbon refrigerants. This study presents results for three typical...
The response of HfB 2 films to nanoindentation and nanoscratch was studied using both experimental and the finite element techniques. The material properties of HfB 2 (elastic modulus, yield strength and Poisson's ratio) were derived by curve-fitting the simulated load–displacement (F–d) nanoindentation data with the experimental F–d data using a parametric analysis. Experimental results...
Hafnium diboride (HfB 2 ) offers an excellent combination of high bulk hardness (29GPa), high melting point (3295°C) and high wear resistance, thus making it an attractive material for wear resistant coatings. In this work, the nanoscale friction response of as-deposited and annealed HfB 2 films is reported. The films were subjected to nanoscratch experimentation and the material response...
The railroad industry in the United States of America spends approximately $2 billion USD yearly on rail replacement and repairs. The Transportation Technology Center Incorporated (TTCI), a wholly owned subsidiary of the Association of American Railroads, Pueblo, Colorado, continuously conducts full scale rail performance tests, which represent a multi-million-dollar investment and take many years...
Scuffing can lead to catastrophic failure in engineering components, but the surface mechanism that leads to scuffing is not well understood. In this experimental study, the surface and subsurface changes on gray cast iron and Al390-T6 were investigated under starved lubrication (a mixture of R410A refrigerant combined with a polyolester lubricant) and pure sliding. Controlled tribological experiments...
Roughness of disk media influences the tribological interaction of head-disk interfaces, especially when the intended flying-height is below 5nm that is required to achieve extremely high-density recording (EHDR). Roughness parameters such as the root-mean-square (RMS) amplitude, however, are influenced by the scale of measurement, such as the scan size. Effects related to scale of measurement such...
A major objective in the development of new rail materials is improving their wear performance. Historically, the main method to accomplish this goal was to manufacture rail steels with higher hardness. However, there is a limit to the hardness that can be achieved with conventional pearlitic rail steels. As a result, there has been an increased focus on improving rail steel hardness with alternative...
Controlled tribological scuffing experiments were conducted on typical engineering surfaces (Al390-T6 discs and 52100 steel pins) under starved lubrication conditions (a mixture of R410A refrigerant combined with a polyolester (POE) lubricant) to simulate the contact conditions in an automotive air conditioning compressor. The time-to-scuff was established and was repeatable using a test protocol...
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