Cylinder Bores Research Articles

Effect of iron oxides on sliding friction of thermally sprayed 1010 steel coated cylinder bores

In-situ Raman spectroscopy was performed on 1010 steel coatings thermally sprayed on an Al-Si alloy on A 380 (Al-9.0% Si) cylinder bore and subjected to reciprocating sliding against various coated rings to investigate the progression of iron oxide formation during sliding. The coatings evaluated for the top compression ring (TCR) included diamond-like carbon (DLC) and chromium nitride (CrN). The reciprocating tests were conducted under unlubricated and boundary lubricated conditions. During unlubricated sliding, a running-in period was observed with increasing coefficient of friction (COF) values which corresponded to the conversion of the initial FeO, present in the as-deposited coating, to Fe3O4 and then to Fe2O3 as identified by changes in Raman spectra obtained at short intervals during the test. Once a Fe2O3 layer was formed, a steady state regime was obtained with a COF of 0.4 that was accompanied by the adhesion of the oxide debris generated during sliding to the counterfaces. The DLC coated TCR provided low steady state COF (0.18) and volumetric wear of 1010 steel, with negligible debris formation. Boundary lubricated sliding tests, with an initial period of unlubricated sliding, resulted in low steady state COF value of 0.10 for DLC and 0.16 for CrN. The low friction and wear of 1010 coatings observed during boundary lubricated sliding against DLC coated TCR was due to a composite tribolayer consisting of an amorphous carbon layer on top of an oil residue layer that was formed on the sliding surfaces.

Multi-surface topography targeted plateau honing for the processing of cylinder liner surfaces of automotive engines

Cylinder bores of automotive engines are ‘engineered’ surfaces that are processed using multi-stage honing process to generate multiple layers of micro geometry for meeting the different functional requirements of the piston assembly system. The final processed surfaces should comply with several surface topographic specifications that are relevant for the good tribological performance of the engine. Selection of the process parameters in three stages of honing to obtain multiple surface topographic characteristics simultaneously within the specification tolerance is an important module of the process planning and is often posed as a challenging task for the process engineers. This paper presents a strategy by combining the robust process design and gray-relational analysis to evolve the operating levels of honing process parameters in rough, finish and plateau honing stages targeting to meet multiple surface topographic specifications on the final running surface of the cylinder bores. Honing experiments were conducted in three stages namely rough, finish and plateau honing on cast iron cylinder liners by varying four honing process parameters such as rotational speed, oscillatory speed, pressure and honing time. Abbott–Firestone curve based functional parameters (Rk, Rpk, Rvk, Mr1 and Mr2) coupled with mean roughness depth (Rz, DIN/ISO) and honing angle were measured and identified as the surface quality performance targets to be achieved. The experimental results have shown that the proposed approach is effective to generate cylinder liner surface that would simultaneously meet the explicit surface topographic specifications currently practiced by the industry.

Transient analysis of residual strain during heat treatment of multi-material engine blocks using in-situ neutron diffraction

Aluminum engine blocks with gray iron cylinder liners are prone to tensile residual stresses along the cylinder bores, which may cause distortion and reduce engine efficiency. This study pioneered the application of in-situ neutron diffraction to measure the residual strain in the cylinder bores of Al engine blocks as a function of time during solution heat treatment, simulated at the spectrometer. This involved designing and incorporating a unique heating system for the engine blocks. The results indicated gradual relief in residual strain with time due to creep until strain was completely relieved. Furthermore, post-treatment cooling led to the development of tensile residual strain due to thermo-mechanical mismatch between the gray iron liners and the surrounding Al alloy.

Optimization of the solution heat treatment process to improve mechanical properties of 319 Al alloy engine blocks using the billet casting method

The use of Al engine blocks has increased significantly to improve vehicle fuel efficiency. However, the large tensile residual stress along the cylinder bores necessitates the optimization of mechanical properties in this region to prevent premature engine failure. This study, utilizing billet castings which replicate the microstructure along the engine cylinder bores, observed the influence of varying solution heat treatment parameters on microstructure and mechanical properties. Microstructural analysis was carried out on the billet castings using optical microscopy, SEM and EDX, while mechanical properties were assessed using tensile testing. The results suggest that the optimal solution heat treatment parameters, resulting in the most effective Al2Cu dissolution and largest increase in tensile properties for all the replicating billet castings, were at 500°C for 2h. In addition, solutionizing at 515 and 530°C, although more effective in dissolving Al2Cu, resulted in incipient melting of Al2Cu and Al5Mg8Cu2Si6, which deteriorated the tensile properties. The results from this study will assist in the development and implementation of an optimized heat treatment schedule, preventing in-service engine failure and improving process efficiency.

Application of the Billet Casting Method to Determine the Onset of Incipient Melting of 319 Al Alloy Engine Blocks

The increased use of Al for automotive applications has resulted from the need to improve vehicle fuel efficiency. Aluminum alloy engine blocks fulfil the need of lightweighting. However, there are many challenges associated with thermo-mechanical mismatch between Al and the gray cast iron cylinder liners, which result in large tensile residual stress along the cylinder bores. This requires improced mechanical properties in this region to prevent premature engine failure. In this study, replicating billet castings were used to simulate the engine block solution heat treatment process and determine the onset of incipient melting. Microstructural changes during heat treatment were assessed with SEM and EDX, while thermal analysis was carried out using differential scanning calorimetry. The results suggest that solution heat treatment at 500 °C was effective in dissolving secondary phase particles, while solutionizing at 515 or 530 °C caused incipient melting of Al2Cu and Al5Mg8Cu2Si6. Incipient melting caused the formation ultra-fine eutectic clusters consisting of Al, Al2Cu, and Al5Mg8Cu2Si6 on quenching. In addition, DSC analysis found that incipient melting initiated at 507 °C for all billets, although the quantity of local melting reduced with microstructural refinement as evidenced by smaller endothermic peaks and energy absorption. The results from this study will assist in improving engine block casting integrity and process efficiency.

Simulation and modeling of friction for honed and wave-cut cylinder bores of marine engines

A fluid solid interaction model (FSI) developed for two different structural cylinder patterns in order to simulate the frictional performance of piston ring–cylinder liner systems for marine engines. Computational fluid dynamics (CFD) analysis is used to solve the Navier Stokes equations. A fully flooded inlet and outlet conditions are assumed taking into account the piston ring elasticity. Honing and wave-cut cylinder geometries were compared while the pressure distribution along the ring thickness and the lubricant film is determined for each crank angle. The present results demonstrate that the honed cylinder geometry improves the friction results increasing the oil film thickness. Further, the artificially textured piston rings with the honed cylinder liner were investigated. As a result, we propose the operational function between the textured rings with the modified cylinder liners in marine engines.

High Performance of Machining Processes by Applying Adaptronic Systems

Manufacturing processes are constantly facing the demand for higher efficiency regarding time, costs and resource consumption. In addition, challenges arise from the use of new materials and stricter requirements concerning the efficiency of the final product in use. Besides the economic perspective of realizing a highly efficient production and sustainable products, a new level of standards is set by politics and industry. To meet these demands, it may no longer suffice to improve processes by optimizing process parameters. Instead, advanced machine and tool concepts will be necessary and therefore have to be developed. An innovative approach to enhance the cutting process is the integration of adaptronic systems. This integration can happen at different levels, from no close loop control to using additional feed drives and in the cutting tool or in the machine. The paper presents examples from research at Fraunhofer IWU for the application of adaptronic systems in machining processes, such as ultrasonic assisted machining, adaptronic form honing and adaptive spindle support for precision finishing of cylinder bores. Properties of the actuators and the adaptronic systems are described and the effects on both, the efficiency of the machining process and the final product performance, are discussed.

Study on the Abrasive Wear of Ceramic Piston Rings and the Different Cylinder Bore

The paper takes the SRV friction and wear tester, conducts the research on the abrasive ability of the three tribomate pairs (ceramic piston ring and P-B, Cu-Cr-Ni-Mo and bainite cylinder bores) under the condition that there lies a certain amount of quartz sand in the lubricant and find that the more hardness of cylinder bores, the more capability of resisting abrasion. The capability of resisting abrasion of ceramic piston ring/bainite cylinder bores is the best in three tribomate pairs.

Formation of an ultrafine grained layer due to high temperature treatment of the surface of a cast iron cylinder bore

In order to meet environmental standards, a finishing laser treatment on the honed cylinder bores of V-engine blocks was performed. Samples of laser-treated cast-iron cylinder bores with lamellar graphite were taken. Scanning electron micrographs were taken on cross-sectioned specimens with a scanning electron microscope/focused ion beam dual beam instrument in order to evaluate the microstructure and grain size of the laser-treated layer. Specimens were found to be ultrafine grained. To simulate the thermal distribution during laser treatment, finite element method simulations were made for different laser energy densities. During laser treatment oil reserving holes were formed due to the inhomogenity of the pearlitic matrix and graphite lamellae, and the high temperature of the laser treatment. To quantify the number of oil reserving holes, a new image analysis method has been developed. It was found that the amount of oil reserving holes increased with higher laser energy densities.

Formation of an ultrafine grained layer due to high temperature treatment of the surface of a cast iron cylinder bore

In order to meet environmental standards, a finishing laser treatment on the honed cylinder bores of V-engine blocks was performed. Samples of laser-treated cast-iron cylinder bores with lamellar graphite were taken. Scanning electron micrographs were taken on cross-sectioned specimens with a scanning electron microscope/focused ion beam dual beam instrument in order to evaluate the microstructure and grain size of the laser-treated layer. Specimens were found to be ultrafine grained. To simulate the thermal distribution during laser treatment, finite element method simulations were made for different laser energy densities. During laser treatment oil reserving holes were formed due to the inhomogenity of the pearlitic matrix and graphite lamellae, and the high temperature of the laser treatment. To quantify the number of oil reserving holes, a new image analysis method has been developed. It was found that the amount of oil reserving holes increased with higher laser energy densities.

Performance impact of honing dynamics on surface finish of precoated cylinder bores

The surface modification of engine cylinder bores with improved sliding properties is often produced by the honing process. This multi-stage process is performed using abrasive stones loaded against the bore with simultaneous rotation and oscillation. To guarantee this process robustness with acceptable dimensional accuracy and surface quality, the stone dynamic effects in continuous balanced contact with the workpiece have to be studied deeply. This paper highlights these effects on honed surface textures. The stone dynamic behavior was studied at conventional regime ranged from 0.5g to 1.5g as often used in mass production. In this range, the dimensional accuracy is ensured by opposition to the surface appearance. However, higher accelerations up to 2.5g improve simultaneously the form quality (especially straightness) and reduce the cycle time. This work shows, at least, that the bore surface finish can be dynamically controlled while honing. This technology is enabled by a micro scale regeneration mechanism of abrasive stones.

Study on the Abrasive Wear of Chromeplate Piston Ring and Cylinder Jacket Made by Different Materials

The abrasion of piston rings/tribomate pairs of cylinder jacket has great damage to engine, which can shorten the life of piston rings and cylinder bore, decrease the power of engine, enlarge the amount of oil, and release more pollution. Take a research of abrasive wear of piston ring and cylinder jacket made by different materials, will create a positive influence on extending the life of engine. This paper takes the SRV friction and wear tester, conducts the research on the abrasive ability of the three tribomate pairs (Cr plated piston ring and P-B, Cu-Cr-Ni-Mo and bainite cylinder bores) under the condition that there lies a certain amount of quartz sand in the lubricant and find that the hardness, intensity and tenacity of tribomate materials can have influence on its capability of resisting abrasion.

Investigation of the surface of a laser-treated cast iron cylinder bore

AbstractThe pollution materials emission standards in Europe are going to be more strict. In order to meet the environmental standards, a European automotive manufacturer performs a finishing laser treatment on the honed cylinder bores of their V-engine blocks. Samples of laser treated cast iron cylinder bores with lamellar graphite were investigated. In order to evaluate the microstructure and grain size of the laser-treated layer, scanning electron micrographs were taken on cross-sectioned samples with a scanning electron microscope/focused ion beam dual-beam instrument. The samples were found to be ultra-fine grained. Nanoindentation hardness measurements of the surface layer showed a clear linear trend between the laser power density in the applied range and the measured hardness. Additional microhardness measurements suggest an annealed region beneath the surface.

Transient elastohydrodynamic lubrication of rough new or worn piston compression ring conjunction with an out-of-round cylinder bore

Real cylinder bores are out-of-round and axially asymmetrical. The top compression ring, nominally an incomplete circle, is subjected to ring tension and cyclic combustion force in order to conform to the bore surface. The bounding surfaces are rough and their conjunction is subject to a transient tribological state. Therefore, the ring–bore conjunction is only partially conforming for most of the engine cycle. The conjunction may be viewed as a problem of scale, depending on the analysis carried out at a certain bore order (out-of-roundness). Therefore, the contact may be viewed as a multi-lobed rough conjunction, where the regime of lubrication may vary from hydrodynamics to mix with dominant asperity friction at piston reversals. Measured bores and ring profiles are used to predict conjunctional power loss and percentage fuel energy consumed. Furthermore, lubricant’s flow through the ring is predicted throughout the engine cycle. These measures are key industrial design drivers for fuel efficiency and reduction of emissions. The results show that the effect of bore out-of-roundness can be even more significant than the surface topography.

TEM analysis and tribological properties of Plasma Electrolytic Oxidation (PEO) coatings on a magnesium engine AJ62 alloy

In order to reduce the fuel consumption and pollution, automotive companies are developing magnesium-intensive components. However, due to the low wear resistance of the magnesium (Mg) alloys, Mg cylinder bores are vulnerable to the sliding wear attack. In this paper, a Plasma Electrolytic Oxidation (PEO) process was used to produce oxide coatings on a Mg alloy AJ62 (MgAl6Mn0.34Sr2), developed for Mg engine block, to battle against the wear attack. The surface morphology, coating thickness and tribological properties were tailored by adjusting the PEO process parameters. TEM analysis demonstrated that the PEO coatings had a nanocrystalline structure in the inner dense layer next to the substrate. The PEO coatings exhibited a much better wear resistance and a smaller friction coefficient than the uncoated AJ62 substrate. The tribological performance of the PEO-coated Mg alloy was even better than that of a hypereutectic Al–Si alloy currently used for engine applications under a high contact load.

Laser Treatment of Cast Iron Engine Cylinder Bore with Nanosecond Laser Pulses

The environmental and polluting materials emission standards in Europe are going to be always stricter, so in order to keep up with them, one of the largest European automotive manufacturer performs a laser treatment on the cylinder bores of their internal combustion engines. Due to the laser treatment, the near surface area of the cylinder bore becomes harder and more wear resistant, furthermore, due to the inhomogenity of the pearlitic matrix and graphite lamellae, oil reserving holes are formed. In our present work we investigated the laser treated layer of cast iron cylinder bores with lamellar graphite. Samples prepared with two different lasertypes and different energies were investigated on behalf of metallographic and functional aspects.

The effects of some laser parameters on the surface and near surface region of laser treated cast iron cylinder bore

The environmental and pollution materials emission standards in Europe are going to be more and more strict. In order to keep the standards, a large European automotive manufacturer makes a laser treatment on the cast iron cylinder bores of the V-engine blocks. Samples of laser treated cast iron cylinder bore with lamellar graphite were investigated. Four samples were treated with Nd-YAG laser and Yb-fiber laser sources in three different configurations. Microhardness measurements were made to evaluate the hardness profile of the treated layer. In order to evaluate the microstructure and grain size of the laser treated layer, scanning electron microscopic (SEM) images were taken in cross section with a SEM/focused ion beam (FIB) dual beam electron microscope. The opened graphite area percent were also determined by image analysis method on the surface after laser treatment with a SEM in backscattered electron (BSE) mode, because the outburned graphite holes are the oil reservoirs for lubrication during operating conditions of the engine.

Effect of leaser treatment on the surface of cast iron cylinder bores

The environmental and pollution materials emission standards in Europe are going to be more strict. In order to meet the standards, a European automotive manufacturer performs a finishing laser treatment on the honed cast iron cylinder bores of their V-engine blocks. Samples of laser treated cast iron cylinder bores with lamellar graphite were investigated. Due to the growing popularity and high efficiency of fiber lasers, samples treated with Yb-fiber lasers were investigated. In order to evaluate the microstructure and grain size of the laser treated layer, scanning electron microscopic images were taken on cross sectioned samples with a scanning electron microscope/focused ion beam dual beam electron microscope. The samples were found to be ultra fine grained. Nanoindentation hardness measurements of the surface layer showed a clear linear trend between the laser power density in the applied range and the measured hardness. Additional micro hardness measurements suggest an annealed region beneath the surfa ce.

Formation of surface layer on cast iron cylinder bore due to nanosecond laser impulses

The air pollution emission standards for automobiles are going to be more strict worldwide. European automotive manufacturer makes a laser treatment on the cast iron cylinder bores of the V-engine blocks. Samples of laser treated cast iron cylinder bore with lamellar graphite were investigated. Seven samples were treated with XeCl-excimerlaser, Nd-YAG laser and Yb-fiber laser sources. In order to evaluate the microstructure and grain size of the laser treated layer, scanning electron microscopic (SEM) images were taken in cross section with a SEM/focused ion beam (FIB) dual beam electron microscopes. All the samples were found to be ultra fine grained. To simulate the heating conditions during laser treatment, finite element method (FEM) simulations were made for the different lasertypes. Additional X-ray diffraction measurements showed retained austenite after laser treatment.

Correlation of Microstructures and Tribological Properties of Ferrous Coatings Deposited by Atmospheric Plasma Spraying on Al-Si Cast Alloy Substrate

The microstructure and tribological properties of ferrous coatings applicable to cylinder bores were investigated in this study. Two kinds of ferrous powders were sprayed on Al-Si cast alloy (EN AlSi10Mg) substrate by atmospheric plasma spraying. Microstructural analysis showed that various Fe oxides were formed in the coatings. The presence of pores, unmelted particles, and Fe precipitates was also noticed. The pin-on-ring tribometer was used to carry out tribological tests under lubricated sliding conditions: sliding speed of 0.5 m/s, sliding distance of 5000 m, and normal load of 450 N. High porosity and the presence of larger and irregularly shaped pores as well as the amount of oxides were the controlling factors for the crack initiations and, consequently, the wear rate. Tribological properties of the coatings were compared with gray cast iron as a standard material for cylinder blocks and showed that, for the investigated conditions, both coatings could be an adequate substitution.