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Technical Paper

Surface and Tribological Characterization of Coatings for Friction and Wear Reduction

The tribological characteristics of three different coated steel plates are compared to a bare steel plate. Coatings included a Ag/Mo coating, and two tungsten disulfide-based coatings. These materials are being considered as alternatives to bare steel and cast iron in automotive engine or powertrain components such as engine cylinders, bearings, and gears. In order to understand their tribological behavior, these coatings have been characterized in terms of surface coating properties, wear resistance, and lubricant interaction between the coating and the additive package in a test grease. Cameron-Plint test results show that the plates coated with Ag/Mo, and both tungsten disulfide-based materials all have lower friction and better wear resistance compared with the bare steel plate. Tungsten disulfide and Ag/Mo-coated plates appear to interact with grease additives. In some cases these specimens formed antiwear films.
Technical Paper

Overview of Techniques for Measuring Friction Using Bench Tests and Fired Engines

This paper presents an overview of techniques for measuring friction using bench tests and fired engines. The test methods discussed have been developed to provide efficient, yet realistic, assessments of new component designs, materials, and lubricants for in-cylinder and overall engine applications. A Cameron-Plint Friction and Wear Tester was modified to permit ring-in-piston-groove movement by the test specimen, and used to evaluate a number of cylinder bore coatings for friction and wear performance. In a second study, it was used to evaluate the energy conserving characteristics of several engine lubricant formulations. Results were consistent with engine and vehicle testing, and were correlated with measured fuel economy performance. The Instantaneous IMEP Method for measuring in-cylinder frictional forces was extended to higher engine speeds and to modern, low-friction engine designs.
Technical Paper

Engine Oil Effects on the Friction and Emissions of a Light-Duty, 2.2L Direct - Injection - Diesel Engine Part 1 - Engine Test Results

The effects of lubricating oil on friction and engine-out emissions in a light-duty 2.2L compression ignition direct injection (CIDI) engine were investigated. A matrix of test oils varying in viscosity (SAE 5W-20 to 10W-40), friction modifier (FM) level and chemistry (MoDTC and organic FM), and basestock chemistry (mineral and synthetic) was investigated. Tests were run in an engine dynamometer according to a simulated, steady state FTP-75 procedure. Low viscosity oils and high levels of organic FM showed benefits in terms of fuel economy, but there were no significant effects observed with the oils with low MoDTC concentration on engine friction run in this program. No significant oil effects were observed on the gaseous emissions of the engine. PM emissions were analyzed for organic solubles and insolubles. The organic soluble fraction was further analyzed for the oil and fuel soluble portions.
Technical Paper

Engine Oil Effects on Friction and Wear Using 2.2L Direct Injection Diesel Engine Components for Bench Testing Part 2: Tribology Bench Test Results and Surface Analyses

The effects of lubricating oil on friction and wear were investigated using light-duty 2.2L compression ignition direct injection (CIDI) engine components for bench testing. A matrix of test oils varying in viscosity, friction modifier level and chemistry, and base stock chemistry (mineral and synthetic) was investigated. Among all engine oils used for bench tests, the engine oil containing MoDTC friction modifier showed the lowest friction compared with the engine oils with organic friction modifier or the other engine oils without any friction modifier. Mineral-based engine oils of the same viscosity grade and oil formulation had slightly lower friction than synthetic-based engine oils.
Technical Paper

Development of a Bench Wear Test for the Evaluation of Engine Cylinder Components and the Correlation with Engine Test Results

A reciprocating motion bench test was developed that uses a modified Cameron-Plint High Frequency Friction Tester for evaluating the friction and wear of engine cylinder bore/piston ring pairs. This paper summarizes the development of such a bench wear test, and the correlation to engine dynamometer tests. The main advantage of the bench test is that parts of real components are tested (cylinder liners and piston rings) so that the geometry and metallurgy of the engine are preserved and representative surface finishes can be tested and evaluated. Precise, quantitative correlation of wear depth is not obtained between the Cameron-Plint bench test and engine dynamometer tests. However, the bench test does rank the various materials and coatings qualitatively in the correct order in terms of wear resistance, and thus provides a valid test for the rough screening of new cylinder bore coatings and materials.
Technical Paper

Assessment of Correlation Between Bench Wear Test Results and Engine Cylinder Wear, Short-Trip Service

Bench tests are often less expensive and faster than vehicle tests. However, correlation between bench tests and the engine needs to be proven, otherwise bench tests may be misleading. This investigation explored the relationships between bench wear test results and engine results from short-trip driving tests for a variety of conditions: fresh vs. used oil, different methods for assessing wear, and chemical effects such as oil contamination and differences in the fuel. There was a negative correlation between bench tests with fresh oil compared to vehicle test results with used oil, which suggests that bench wear characteristics of fresh engine oil should not be used to determine engine wear rates under the conditions tested here. Statistical analysis of bench test wear rates with used engine oil, compared to engine wear measurements, indicated that the trends were in an appropriate direction, with some scatter in the results.
Technical Paper

An Investigation of Tribological Characteristics of Energy-Conserving Engine Oils Using a Reciprocating Bench Test

Engine design and tribology engineers are constantly challenged to develop advanced products with reduced weight, reduced friction, longer life, and higher engine operating temperatures. The resulting engine systems must also meet more demanding emissions and fuel economy targets. Advanced energy-conserving lubricants and surface coatings are concurrently evolving to meet the needs of new engine materials. Because of the enormous cost and time associated with engine testing, much interest is being focused on the development of representative and repeatable bench tests for evaluation of engine materials and lubricants. The authors have developed a bench test employing reciprocating motion for evaluating friction and energy-conserving characteristics of lubricants.
Technical Paper

A Test Method for Evaluating Material Combinations of Automotive Camshaft and Follower Components Subjected to Lubricated Sliding Simulating Variable Valve Actuation

Cam phasing and Variable Valve Actuation (VVA) are used increasingly to alter the opening and closing of the valves to improve fuel economy by most of the automotive engine manufacturers. In instances where the design constraints require use of rolling and sliding follower interfaces with camshaft lobes, several solutions are possible. However, finding an inexpensive solution is challenging. This paper briefly reviews some of the conventional wear test methods that have primarily been used for piston ring cylinder liner wear assessments. Later on a new test method developed using the modified Optimol SRV 4 wear tester is described. This test method was used to assess and rank material combinations for sliding wear assessment of various camshaft lobe and follower components.