Method for treating cylindrical tracks of cylinders or cylindrical sleeves by laser application

Abstract

The present invention relates to a method for treating cylindrical tracks of cylinders or cylindrical sleeves, the method comprising the contactless application of a pulsed laser beam to a honed surface (5) of the cylindrical track or cylindrical sleeve, wherein the honed surface (5) has honing channels (7) and / or secondary channels, wherein the application of the pulsed laser beam is configured such that cementite portions (2) on the honed surface (5) are remelted to form a cementite layer (8).

Description

METHOD FOR TREATING CYLINDER RUNWAYS OF CYLINDERS OR CYLINDER LINERS BY LASER IMPACT Technical area

[0001] The present invention relates to a method for treating cylinder bores of cylinders or cylinder liners for reciprocating piston engines. Technical background

[0002] Cylinder bores, or cylinder liners, are critical components in reciprocating engines that provide a durable surface for piston movement and combustion processes. These liners can be made of lamellar graphite cast iron with a pearlitic structure containing cementite, ferrite, and graphite flakes. The surface properties of cylinder liners have a significant impact on engine performance, efficiency, and longevity.

[0003] Over time, cylinder liners are exposed to extreme conditions, including high temperatures, pressures, and mechanical stress. This can lead to wear, deterioration of surface properties, and the accumulation of combustion residues in the honing grooves and secondary grooves of the liner surface. These factors can negatively impact engine performance, increase oil consumption, and potentially shorten engine life.

[0004] Various methods have been used to improve the surface properties of cylinder liners, including honing processes to create a cross-grain pattern that aids oil retention and distribution. However, conventional honing processes do not always provide optimal surface properties for modern high-performance engines.

[0005] There is a continuing need for improved processes and technologies for the treatment of cylinder bores and Cylinder liners, both in the manufacture of new engines and in the remanufacturing of used engines. Advances in this area could lead to engines with better performance, increased efficiency, reduced emissions, and extended service life. Description

[0006] Based on the known state of the art, it is The object of the present invention is to provide an improved method for treating cylinder bores of cylinders or cylinder liners of reciprocating piston engines, in particular for improving the surface properties of the cylinder bores of the cylinders or cylinder liners.

[0007] This object is achieved by a method having the features of claim 1. Advantageous further developments emerge from the dependent claims, the description, and the figures.

[0008] According to one aspect of the present disclosure, a method for treating cylinder bores of cylinders or cylinder liners is proposed, wherein the method comprises the steps of contactlessly applying a pulsed laser beam to a honed surface of the cylinder bore or cylinder liner, wherein the honed surface has honing grooves and / or secondary grooves, and wherein the application of the pulsed laser beam is arranged such that cementite components on the honed surface are remelted to form a cementite layer.

[0009] Cementite, also known as iron carbide, has, among other things, a very high hardness, so the cementite layer on the honed surface leads to increased stability and wear resistance of the cylinder surface or cylinder liner. In this way, the process can improve the fatigue strength of the cylinder surfaces or cylinder liners.

[0010] The cylinder bore of the cylinder or the cylinder liner may comprise or consist of lamellar graphite cast iron with a pearlitic structure and may comprise cementite components, ferrite components and graphite lamellar components, wherein the application of the pulsed laser beam may further be arranged such that graphite lamellar components are exposed on the honed surface and ferrite components are evaporated.

[0011] In this way, the tribological properties of the honed surface can be improved, as exposing the graphite flakes improves oil retention and lubrication. This leads to improved wear resistance, improved oil retention, and extended engine life, thus improving the properties of the treated engine.

[0012] For the treatment of honing grooves and / or secondary grooves clogged by combustion residues, in particular by combustion residues in the form of oil carbon in a liquid fuel engine or varnish in a gas engine, the pulsed laser beam can be configured to remove the combustion residues in the honing grooves and / or the secondary grooves of the honed surface by evaporation.

[0013] This means the process can be used not only for machining new cylinder bores or cylinder liners, but also for reconditioning existing cylinder bores or cylinder liners. The process is therefore particularly flexible.

[0014] In particular, the above-mentioned advantages can be achieved with a single treatment using the pulsed laser beam. This treatment can achieve remelting of the cementite components into the cementite layer, exposure of the graphite flake components, evaporation of the ferrite components, and cleaning by evaporation of the combustion residues in a single process step of exposing the honed surface to the pulsed laser beam.

[0015] The application of the pulsed laser beam can be repeated until the cementite layer is formed on the honed surface as a largely closed surface or a completely closed surface, preferably with a homogeneous surface structure.

[0016] A largely closed surface of the cementite layer is understood, for example, to mean one in which the cementite layer extends over all areas of the honed surface, but excluding the honing grooves and / or secondary grooves. In other words, no cementite layer is formed in the honing grooves or secondary grooves.

[0017] A completely closed surface of the cementite layer is understood, for example, to mean one in which the cementite layer is present over the entire honed surface, including the honing grooves and / or secondary grooves. The cementite layer follows the surface contour, so that the honing grooves and secondary grooves are still present but covered with a cementite layer.

[0018] The cementite layer can be formed in a thickness of 2 nm to 1 pm, preferably 3-10 nm.

[0019] The pulsed laser beam can be configured to round off sharp-edged structures and / or edges of honing grooves and / or protruding material tongues and / or edges of secondary grooves by melting during the application of the pulsed laser beam to the honed surface, in particular to improve the tribological properties of the honed surface.

[0020] By rounding off the above-mentioned structures, wear on the honed surface can be reduced and the tribological properties are improved by homogenizing the surface.

[0021] The pulsed laser beam can be configured to melt and / or redistribute material on the honed surface to produce a more uniform surface structure with reduced sharp edges and projections compared to the surface structure before exposure to the pulsed laser beam.

[0022] This can also improve wear on the treated surface.

[0023] The pulsed laser beam can have an average laser power of 90-300W, a wavelength of 1060-1070nm, a pulse frequency of 135-165kHz and a pulse width of 18-22ns.

[0024] In this way, the above-mentioned advantages can be achieved.

[0025] The object described above is further achieved by a method for treating cylinder bores of cylinders or cylinder liners having a honed surface with honing grooves and / or secondary grooves, wherein the honed surface is exposed to a pulsed laser beam, wherein the pulsed laser beam has an average laser power of 90-300W, a wavelength of 1060-1070nm, a pulse frequency of 135-165kHz and a pulse width of 18-22ns.

[0026] The above-mentioned treatment steps and advantages can be achieved with an appropriately configured pulsed laser beam for impacting the honed surface.

[0027] The average laser power can be adjusted for all of the above-mentioned processes and process variants depending on the amount of combustion residue on the honed surface. For a new honed surface not contaminated with combustion residue, the average laser power is preferably adjusted to 90-110W; for a honed surface lightly contaminated with combustion residue, the average laser power is adjusted to 125-155W; and for a honed surface heavily contaminated with combustion residue, the average laser power is adjusted to 180-220W.

[0028] As already described, the process can be very flexible and independent of the current condition of the honed surfaces New and used cylinder bores or cylinder liners can be treated accordingly.

[0029] The application of the pulsed laser beam can be arranged in such a way that graphite flake components are exposed on the honed surface, ferrite components are evaporated and remaining cementite components are remelted to form a cementite layer, wherein the cylinder bore of the cylinder or the cylinder liner comprises or consists of flake graphite cast iron with a pearlitic structure and comprises cementite components, ferrite components and graphite flake components.

[0030] The pulsed laser beam can be applied to the honed surface by means of an optical arrangement in such a way that the honed surface is exposed to a processing spot with a length of 28-32 nm and a width of 1.9-2.0 mm.

[0031] The pulsed laser beam can be moved over the honed surface at a scanning speed of 7200-8800mm / s in order to expose it to the laser beam.

[0032] By scanning the surface in this way, the entire honed surface can be exposed to the pulsed laser beam, thus processing all areas of the honed surface. Using the scanning described above, it is possible to easily adapt the treatment to the specific geometry and dimensions of the honed surface.

[0033] The individual pulses of the pulsed laser beam can have a single pulse energy of up to 1.8 mJ, preferably 0.2-2.5 pJ.

[0034] This allows for reliable and fast processing.

[0035] The procedure can be carried out while an engine is installed.

[0036] This allows for a particularly high level of surface finish when reconditioning cylinder bores or cylinder liners that have already been used. carry out particularly simple and efficient treatment without having to disassemble the engine to a large extent.

[0037] The above-mentioned object is also achieved by a cylinder or cylinder liner of a reciprocating piston engine having a honed surface with honing grooves and / or secondary grooves, wherein the honed surface has a cementite layer with a thickness of 2 nm to 1 pm, preferably of 3-10 nm.

[0038] Such a cylinder or cylinder liner offers the advantage of improved wear resistance, improved oil retention and extended service life due to the unique surface structure created by the laser treatment process.

[0039] The cementite layer can be largely closed or closed and preferably form a homogeneous surface structure, wherein the cementite layer particularly preferably extends over the entire honed surface.

[0040] A largely closed surface of the cementite layer is understood, for example, to mean one in which the cementite layer extends over all areas of the honed surface, but excluding the honing grooves and / or secondary grooves. In other words, no cementite layer is formed in the honing grooves or secondary grooves.

[0041] A completely closed surface of the cementite layer is understood, for example, to mean one in which the cementite layer is present over the entire honed surface, including the honing grooves and / or secondary grooves. The cementite layer follows the surface contour, so that the honing grooves and secondary grooves are still present but covered with a cementite layer.

[0042] The cylinder or cylinder liner may comprise a pearlitic structure with cementite, ferrite and graphite flakes, and graphite flakes may be present on the honed surface must be exposed and ferrite components removed, preferably evaporated.

[0043] Sharp-edged structures and / or edges of honing grooves and / or protruding material tongues and / or edges of secondary grooves can be rounded by melting.

[0044] The cementite layer on the honed surface can be formed as a largely closed surface or as a closed surface, preferably with a homogeneous surface structure, particularly preferably on the entire honed surface.

[0045] Graphite flakes on the honed surface may be exposed and create a network of exposed graphite flakes, thereby improving the tribological properties of the surface.

[0046] The method and device for laser treatment of cylinder bores or cylinder liners offer several technical advantages. First, the laser treatment process simultaneously achieves several beneficial effects in a single operation. It effectively removes combustion residues and contaminants from the honed surface, including clogged honing grooves and secondary grooves, through evaporation. This cleaning action restores the original tribological properties of the surface texture, which is crucial for proper lubrication and reduced friction during engine operation.

[0047] At the same time, the laser treatment exposes graphite flakes on the honed surface. This exposure of graphite flakes improves the self-lubricating properties of the cylinder liner material, which further contributes to reducing friction and wear during engine operation.

[0048] The laser-induced thermal effects also lead to the rounding of sharp-edged structures, honing grooves, and protruding material tongues. This rounding effect creates a more uniform Surface topography that is less susceptible to the accumulation of combustion residues and has improved tribological properties.

[0049] Laser treatment can transform the surface microstructure by evaporating ferrite components and melting remaining cementite components into a cementite layer. This cementite layer, with a thickness of a few nanometers to 1 pm, forms a ceramic-like structure on the honed surface. The presence of this cementite layer significantly improves the wear resistance of the cylinder liner and extends its service life. Furthermore, the cementite layer exhibits a reduced material affinity for friction partners such as piston rings and piston skirts, which reduces the tendency toward adhesive wear.

[0050] The versatility of the process is another important advantage. It can be applied to both new cylinder liners and honed surfaces lightly or heavily contaminated with combustion residues, with the laser parameters being able to be adapted to different surface conditions. This flexibility enables the treatment of engines at various stages of their life cycle, from manufacturing to maintenance and reconditioning.

[0051] Furthermore, the procedure can be performed with the cylinder liners installed in the engine, requiring only the removal of the cylinder head. This in-situ capability significantly reduces maintenance time and costs compared to conventional remanufacturing methods, which may require complete engine disassembly or cylinder liner replacement.

[0052] Finally, the process offers excellent process control and repeatability. The ability to visually inspect the treated surface or use automated magnetic wave-induced surface inspection techniques ensures consistent Quality and reduces dependence on subjective human judgment. This feature is particularly valuable in industrial applications where consistency and quality control are paramount. Short description of the drawings

[0053] Preferred further embodiments of the invention are explained in more detail with reference to the following description of the figures. The figures show:

[0054] Figure 1 shows a schematic cross-sectional view of a honed surface of a cylinder bore of a cylinder of a reciprocating engine or a cylinder liner before treatment and at an approximately 800x magnification of the cross-section.

[0055] Figure 2 shows a schematic cross-sectional view of the honed surface of Figure 1 after treatment with a laser beam according to aspects of the present disclosure.

[0056] Figure 3 shows a scanning electron microscope image of an untreated honed surface.

[0057] Figure 4 shows a scanning electron microscope image of a honed surface after treatment by exposure to a laser beam in accordance with aspects of the present disclosure. Detailed description of the characters

[0058] Preferred embodiments are described below with reference to the figures. Identical, similar, or equivalent elements in the various figures are provided with identical reference numerals, and a repeated description of these elements is partially omitted to avoid redundancy.

[0059] The present disclosure provides a method for treating cylinder bores of cylinders or cylinder liners for a reciprocating piston engine, particularly those made of lamellar graphite cast iron. This process uses a pulsed laser for the non-contact treatment of a honed surface of the cylinder bore or cylinder liner, wherein the honed surface has honing grooves and / or secondary grooves.

[0060] The initial application of the pulsed laser beam to the honed surface serves to melt cementite particles on the honed surface into a cementite layer. This creates a hard and wear-resistant honed surface.

[0061] Exposure to the honed surface can also expose graphite flakes on the honed surface and vaporize ferrite particles. If combustion residues are present on the honed surface, these can also be vaporized by exposure to the pulsed laser. This simultaneous cleaning, restructuring, and improvement of the surface properties of the honed surface can lead to improved engine performance and longevity.

[0062] The process is versatile and can be applied to new, lightly contaminated, and heavily contaminated honed surfaces, with treatment parameters adaptable to the varying conditions of the honed surface prior to treatment. This flexibility enables the treatment of engines at various stages of their life cycle, from manufacturing to maintenance and remanufacturing.

[0063] With reference to Figures 1 and 2, these figures show a section of a cylinder, in particular a cylinder bore, or a cylinder liner, which in the example shown each comprise a pearlitic structure 1.

[0064] In the schematic cross-sectional views, a honed surface 5 is shown, which in Figure 1 before treatment by means of the Exposure to the pulsed laser beam, and shown in Figure 2 after this treatment.

[0065] The cylinder with the cylinder bore or the cylinder liner consists of or comprises lamellar graphite cast iron having a pearlitic structure 1. This structure 1 comprises cementite components 2, ferrite components 3 and graphite flake components 4. The honed surface 5 comprises honing grooves 7 and / or secondary grooves.

[0066] A pulsed laser is used to treat the honed surface 5 without contact. This treatment process involves exposure to the pulsed laser beam. As previously mentioned, exposure to the pulsed laser beam can remelt cementite particles 2 on the honed surface 5 into a cementite layer 8. This remelting process can improve the surface properties of the honed surface 5, thus improving the cylinder bore or cylinder liner and creating a more durable and efficient surface for engine operation.

[0067] Furthermore, exposure to the pulsed laser can expose graphite flakes 4 on the honed surface 5. This exposure of the graphite flakes 4 can improve the tribological properties of the honed surface 5 and thus increase the performance and longevity of the engine.

[0068] Exposure to the pulsed laser beam can also vaporize ferrite particles 3. This vaporization process can also clean the honed surface 5 and remove unwanted materials and contaminants.

[0069] In the case of a new cylinder bore or cylinder liner that has not yet been in operation, a honed surface 5 can be provided in this way, which is free of all residues and additives that were left over during the production of the honed surface 5, such as chips or honing oil. This allows a Gentle running-in of the engine with reduced abrasion can be achieved, which thus contributes to an improvement in the service life of the engine.

[0070] The laser treatment process can be applied to new, lightly contaminated with combustion residues 6 and heavily contaminated with combustion residues 6 honed surfaces 5.

[0071] In some aspects, the laser parameters can be adjusted to accommodate different surface conditions. This flexibility enables the treatment of engines at various stages of their life cycle, from manufacturing to maintenance and remanufacturing.

[0072] In other words, the treatment involves remelting a pearlitic structure 1 into a closed cementite layer 8. The formation of this cementite layer 8 can improve the surface properties of the cylinder liner and thus increase the performance and durability of the engine.

[0073] Treatment by exposure to the laser beam can have a significant impact on the surface structure of the honed surface 5. For example, the honing grooves 7 and / or secondary grooves on the surface 5 of the cylinder bore may be clogged with combustion residues 6 or dirt. These combustion residues may include, for example, carbon deposits in a liquid fuel engine powered by diesel, light oil, or heavy oil, or varnish deposits in a gas engine powered by natural gas, for example. Exposure to the laser beam during treatment can expose these grooves again by evaporating the combustion residues 6.

[0074] This cleaning process can restore the functionality of the grooves and thus enable them to once again effectively contribute to the tribological properties of the honed surface 5.

[0075] In addition or as an alternative to cleaning the scouring marks and / or secondary marks, the treatment can be carried out by applying The pulsed laser beam can also round off sharp-edged structures on the honed surface 5 of the cylinder bore. These structures can include edges of honing grooves 7 and / or protruding material tongues and / or edges of secondary grooves. The rounding process is achieved by melting these structures during exposure to the laser beam. This can lead to a smoother surface structure with reduced sharp edges and protrusions compared to the surface structure before treatment with the pulsed laser beam.

[0076] This rounding process can improve the tribological properties of the surface and reduce friction and wear during engine operation, thus also restoring the longevity of the engine.

[0077] In the case of a new cylinder bore or cylinder liner that has not yet been in operation, a honed surface 5 can be provided in this way, which enables gentle running-in of the engine with reduced abrasion and thus contributes to an improvement in the service life of the engine.

[0078] Treatment with the pulsed laser beam can also redistribute material on the honed surface 5. This is achieved by partially melting the material on the honed surface 5 during exposure to the laser beam. The molten material is then redistributed on the honed surface 5 to fill gaps and smooth irregularities. This can result in a more uniform surface structure with reduced roughness compared to the surface structure before laser treatment.

[0079] The pulsed laser beam applied to the honed surface 5 may have an average laser power of 90-300W, a wavelength of 1060-1070nm, a pulse frequency of 135-165kHz and a pulse width of 18-22ns.

[0080] The laser power can be adjusted depending on the amount of combustion residue 6 deposited on the honed surface 5. For a new honed surface 5 not contaminated with combustion residue 6, the average laser power can be adjusted to 90-110W. For a honed surface 5 lightly contaminated with combustion residue 6, the average laser power can be adjusted to 125-155W. For a honed surface 5 heavily contaminated with combustion residue 6, the average laser power can be adjusted to 180-220W.

[0081] The individual pulses of the pulsed laser beam can have a single pulse energy of up to 1.8 mJ, preferably 0.2-2.5 pJ.

[0082] These settings are designed to effectively treat the cylinder bores or cylinder liners without causing unnecessary damage or wear.

[0083] In order to enable a complete treatment of the honed surface 5, the pulsed laser beam can be applied to the honed surface 5 by means of an optical arrangement such that the honed surface 5 is exposed to a processing spot with a length of 28-32 nm and a width of 1.9-2 nm.

[0084] The pulsed laser beam can be guided over the honed surface 5 at a scanning speed of 7200-8800 mm / s in order to expose it to the pulsed laser beam.

[0085] The exposure of the honed surface 5 to the laser beam can be carried out or repeated until the cementite layer 8 is formed on the honed surface 5 as a largely closed surface with a homogeneous surface structure. This cementite layer 8 is preferably achieved on the entire honed surface 5.

[0086] This repetition of the laser beam exposure can ensure that the entire honed surface 5 is treated evenly, resulting in a consistent and uniform cementite layer 8 over the entire surface.

[0087] The formation of the cementite layer achieved by applying the pulsed laser beam to the honed surface 5 can lead to a cementite layer 8 with a thickness of 2 nm to 1 pm, preferably 3-10 nm.

[0088] This can improve overall engine performance and longevity by providing a consistent and durable surface for engine operation.

[0089] Referring to Figures 3 and 4, these schematic diagrams show scanning electron microscope images of honed surfaces at different stages of treatment.

[0090] Figure 3 shows a cross-sectional view of an untreated honed surface. The pearlitic microstructure 1 is visible as the base material. A layer of combustion residues 6 is present on the honed surface and appears as a dark band at the top of the image. The scale bar indicates that the layer of combustion residues has a thickness of a few microns.

[0091] Figure 4, on the other hand, shows a cross-sectional view of a honed surface after laser treatment. The pearlitic microstructure 1 remains visible as the base material.

[0092] A graphite flake 4 can be seen extending from the base material to the surface. This exposure creates a network of exposed graphite flakes that improves the surface's oil retention properties. This can improve engine performance and longevity by reducing friction and wear during operation.

[0093] The laser treatment also led to the formation of a cementite layer 8, visible as a bright band along the upper surface. This cementite layer 8 appears more uniform and continuous compared to the layer of combustion residues 6 in Figure 3. Scale bar shows that the thickness of the cementite layer 8 is well below one pm.

[0094] The comparison between Figures 3 and 4 shows the effects of laser treatment on the honed surface, including the removal of combustion residues and the formation of the cementite layer 8. The cementite layer 8 has a thickness of 2 nm to 1 pm in some aspects, preferably 3-10 nm. This layer provides a durable and efficient surface for engine operation.

[0095] In some aspects, a cylinder liner treated with the laser process differs visibly from an untreated cylinder liner. This difference can be observed under a scanning electron microscope, as shown in Figures 3 and 4. The treated cylinder liner exhibits a more uniform and continuous cementite layer 8, reduced combustion residues, and exposed graphite flakes. These changes in surface structure and composition resulting from the laser treatment process can lead to improved engine performance and durability.

[0096] In some aspects, the laser used to deliver the laser beam for the treatment procedure is a pulsed laser. The pulsed laser may have a wavelength of 1,060 to 1,070 nm, a pulse width of 10 to 500 ns, a pulse frequency of 1 to 4,000 kHz, and a maximum single pulse energy of up to 1.8 mJ.

[0097] In some cases, this is specifically an Nd:YAG laser with a wavelength of 1064 nm. This type of laser is known for its high power and precision, making it suitable for the treatment of cylinder liners.

[0098] In some aspects, the method for treating cylinder bores of cylinders or cylinder liners is performed in the installed state of an engine. This feature allows the treatment process to be carried out without extensive disassembly of the engine, reducing downtime and labor costs. In some cases, the laser device or its exit optics used in the process are mounted on a linear actuator. This arrangement can facilitate the movement of the laser device or its exit optics along the length of the cylinder bore and ensure uniform treatment of the entire surface.

[0099] In some embodiments, the method is performed under a range of environmental conditions. For example, the method can be performed at a relative humidity of 10 to 95% and a permissible room temperature of 0 to 40°C. This flexibility in environmental conditions allows the method to be implemented in a variety of environments, from controlled indoor spaces to outdoor locations with varying weather conditions.

[0100] In some cases, the process results in the coagulation of the internal roughness of the cylinder liner. This coagulation process involves the partial melting and redistribution of material on the cylinder liner surface during laser beam exposure. This can result in a more uniform surface structure with reduced roughness compared to the surface structure before laser treatment. This can improve the tribological properties of the surface and reduce friction and wear during engine operation.

[0101] In some aspects, the process is performed manually. This feature allows the treatment process to be performed without the need for complex machinery or automated systems. This can make the process more accessible and cost-effective, especially for smaller shops or in situations where access to advanced equipment is limited. Although performed manually, the process can still achieve effective and uniform treatment of the honed surface thanks to the precision and control provided by the laser device.

[0102] In some aspects, the results of the laser treatment process on the honed surface can be inspected and verified using various methods. One such method involves visual inspection based on clearly observable changes in the surface texture of the honed surface. After the laser treatment process, the cylinder bore surface may exhibit a more uniform and continuous cementite layer 8, reduced combustion residues, and exposed graphite flakes. These changes in surface structure and composition can be visually observed and provide a simple and accessible way to verify the results of the laser treatment process.

[0103] In some cases, automated techniques can be used to inspect and verify the results of the laser treatment process. For example, automated magnetic wave-induced surface inspection, also known as the Tom's Check method, can be employed. This method involves the use of magnetic waves to inspect the surface of the cylinder bore. The magnetic waves can detect changes in surface structure and composition, providing a detailed and accurate assessment of the results of the laser treatment process. This automated inspection method can be particularly useful in situations where a high degree of precision and accuracy is required, or where human factors such as fatigue or changing daily routines can compromise the reliability of visual inspection.

[0104] In some aspects, the inspection and verification methods can be combined to provide a comprehensive evaluation of the results of the laser treatment process. For example, visual inspection can be used for a preliminary assessment of surface changes, followed by automated magnetic wave-induced surface inspection for a more detailed and accurate evaluation. Combining methods can ensure that the laser treatment process has effectively treated the honed surface, improving its tribological properties and increasing engine performance and longevity.

[0105] In some aspects, the quality of the laser-treated honed surface can be determined by various methods. One such method may involve the use of profilometry techniques to measure surface roughness parameters. For example, a stylus or optical profilometer may be used to measure the arithmetic mean roughness (Ra), root mean square roughness (Rq), and maximum peak-to-valley height (Rz) of the treated surface. These measurements can provide quantitative data on the smoothness and uniformity of the surface after laser treatment.

[0106] In some cases, the surface structure of the laser-treated cylinder bore can be determined experimentally using advanced microscopy techniques. Scanning electron microscopy (SEM) can be used to visualize the surface topography at high magnification and reveal details of the cementite layer 8, exposed graphite lamellae 4, and remaining honing marks 7. Additionally, atomic force microscopy (AFM) can be used to create three-dimensional maps of the surface and provide nanometer-scale resolution of the surface features.

[0107] In some aspects, X-ray diffraction (XRD) analysis can be performed to determine the crystal structure of the laser-treated surface. This technique can confirm the presence and relative abundance of cementite in the newly formed layer 8, as well as detect changes in the underlying pearlitic microstructure 1.

[0108] Various measurements can be taken on the laser-treated honed surface to assess its quality and properties. In some cases, the thickness of the cementite layer 8 can be measured by Cross-sectional SEM or transmission electron microscopy (TEM) can be measured. The thickness of this layer can range from a few nanometers to 1 pm, depending on the specific laser treatment parameters used.

[0109] In some aspects, the method includes adjusting the treatment parameters and laser parameters depending on the condition of the cylinder liner surface. For new cylinder liners, the treatment may not need to include cleaning the surface of oil carbon or gas varnish, as these contaminants are typically not present on unused liners. However, the treatment may still include cleaning honing residues such as honing oil. In this case, the laser parameters can be adjusted to focus primarily on exposing graphite flakes and forming the cementite layer, rather than on removing combustion residues.

[0110] For lightly used cylinder liners, the process may include a mild cleaning process to remove light deposits of carbon or gas varnish. The laser parameters can be adjusted to provide sufficient energy for cleaning while maintaining the focus on the surface restructuring process. In some cases, the laser power can be increased by 5-10% compared to the parameters used for new liners, and the pulse frequency can be adjusted to optimize the cleaning effect.

[0111] For heavily used cylinder liners with significant deposits of carbon or gas varnish, the process may involve a more intensive cleaning process. The laser parameters can be adjusted to provide higher energy for effective removal of these deposits. In some aspects, the laser power can be increased by 15-25% compared to the parameters used for new liners, and the pulse width can be extended to enable more thorough evaporation of contaminants. The scanning speed can also be reduced to ensure sufficient exposure time for cleaning and surface restructuring.

[0112] In some cases, the process may include a pretreatment assessment of the honed surface to determine its condition and the presence of contaminants. This assessment may include visual inspection, profilometry measurements, or spectroscopic analysis to characterize the surface composition. Based on this assessment, the laser parameters and treatment process can be tailored to the specific condition of each cylinder liner to ensure optimal results regardless of its usage history.

[0113] The method and apparatus described here for laser treatment of cylinder bores and cylinder liners have wide-ranging industrial applications, particularly in the automotive, marine, and heavy engineering industries. This technology is suitable for industrial application in engine manufacturing, maintenance, and remanufacturing. It can be implemented both in production lines for new engines and in repair and overhaul facilities for used engines. The versatility of the method allows its application to various types and sizes of engines, from small automotive engines to large marine diesel engines. While the examples cited focus on internal combustion engines, the principles and techniques of this invention can be adapted for use in other industries where precise surface treatment of cylindrical bores is required, such as:in hydraulic systems, pneumatic cylinders, or even in the aerospace industry for the treatment of engine components. The scalability and adaptability of this laser treatment process make it a valuable tool for improving the performance, efficiency, and longevity of a wide range of industrial machinery and equipment.

[0114] Where applicable, all individual features presented in the embodiments may be combined and / or exchanged for one another without departing from the scope of the invention. List of reference symbols 1 pearlitic structure 2 cementite content 3 Ferrite content 4 graphite flakes 5 honed surface 6 Combustion residue 7 Honing groove 8 cementite layer

Claims

Claims 1. A method for treating cylinder bores of cylinders or cylinder liners, the method comprising the steps of: contactless application of a pulsed laser beam to a honed surface (5) of the cylinder bore or cylinder liner, the honed surface (5) having honing grooves (7) and / or secondary grooves, the application of the pulsed laser beam being arranged such that cementite portions (2) on the honed surface (5) are remelted to form a cementite layer (8).

2. Method according to claim 1, wherein the cylinder bore of the cylinder or the cylinder liner comprise or consist of lamellar graphite cast iron with a pearlitic structure (1) and comprise cementite portions (2), ferrite portions (3) and graphite lamellar portions (4), wherein the application of the pulsed laser beam is further arranged such that graphite lamellar portions (4) are exposed on the honed surface (5) and ferrite portions (3) are evaporated.

3. Method according to claim 1 or 2, wherein for the treatment of honing grooves (7) and / or secondary grooves clogged by combustion residues (6), in particular by combustion residues (6) in the form of oil carbon in a liquid fuel engine or varnish in a gas engine, the pulsed laser beam is configured to remove the combustion residues (6) in the honing grooves (7) and / or the secondary grooves of the honed surface (5) by evaporation.

4. Method according to one of the preceding claims, wherein the application of the pulsed laser beam is repeated until the cementite layer (8) on the honed surface (5) is formed as a largely closed or completely closed surface, preferably with a homogeneous surface structure.

5. Method according to one of the preceding claims, wherein the cementite layer (8) is formed in a thickness of 2 nm to 1 pm, preferably in a thickness of 3-10 nm.

6. Method according to one of the preceding claims, wherein the pulsed laser beam is arranged such that it rounds off sharp-edged structures and / or edges of honing grooves (7) and / or protruding material tongues and / or edges of secondary grooves by melting during the application of the pulsed laser beam, in particular in order to improve the tribological properties of the honed surface (5).

7. Method according to one of the preceding claims, wherein the pulsed laser beam is arranged to melt and / or redistribute material on the honed surface (5) in order to achieve a more uniform surface structure with reduced sharp edges and protrusions compared to the surface structure before exposure to the pulsed laser beam.

8. Method according to one of the preceding claims, wherein the pulsed laser beam has an average laser power of 90-300W, a wavelength of 1060-1070nm, a pulse frequency of 135-165kHz and a pulse width of 18-22ns.

9. Method for treating cylinder bores of cylinders or cylinder liners having a honed surface (5) with honing grooves (7) and / or secondary grooves, wherein the honed surface (5) is exposed to a pulsed laser beam, wherein the pulsed laser beam has an average laser power of 90-300W, a wavelength of 1060-1070nm, a pulse frequency of 135-165kHz and a pulse width of 18-22ns.

10. The method according to claim 8 or 9, wherein the average laser power is adjusted depending on the load of the honed surface (5) with combustion residues (6), and preferably for a new honed surface (5) not loaded with combustion residues (6), the average laser power is adjusted to 90-110W, for a honed surface (5) slightly loaded with combustion residues (6), the average laser power is adjusted to 125-155W, and for a honed surface (5) heavily loaded with combustion residues (6), the average laser power is adjusted to 180-220W.

11. The method according to claim 9 or 10, wherein the application of the pulsed laser beam is arranged such that graphite flake portions (4) are exposed on the honed surface (5), ferrite portions (3) are evaporated and remaining cementite portions (2) are remelted to form a cementite layer (8), wherein the cylinder bore of the cylinder or the cylinder liner comprises or consists of flake graphite casting with a pearlitic structure (1) and comprises cementite portions (2), ferrite portions (3) and graphite flake portions (4).

12. Method according to one of the preceding claims, wherein the pulsed laser beam is applied to the honed surface (5) by means of an optical arrangement such that the honed surface (5) is provided with a Processing spot with a length of 28-32nm and a width of 1.9-2.0 mm.

13. Method according to one of the preceding claims, wherein the pulsed laser beam is guided over the honed surface (5) at a scanning speed of 7200-8800 mm / s in order to expose it to the laser beam.

14. Method according to one of the preceding claims, wherein the individual pulses of the pulsed laser beam have an individual pulse energy of up to 1.8 mJ, preferably 0.2-2.5 pJ.

15. Method according to one of the preceding claims, wherein the method is carried out in the installed state of an engine.

16. Cylinder or cylinder liner of a reciprocating piston engine, which has a honed surface (5) with honing grooves (7) and / or secondary grooves, wherein the honed surface (5) has a cementite layer (8) with a thickness of 2 nm to 1 pm, preferably with a thickness of 3-10 nm.

17. Cylinder or cylinder liner according to claim 16, wherein the cementite layer (8) is closed or largely closed and preferably forms a homogeneous surface structure, wherein the cementite layer (8) particularly preferably extends over the entire honed surface (5).

18. Cylinder or cylinder liner according to claim 16 or 17, wherein the cylinder bore of the cylinder or the cylinder liner comprises a pearlitic structure (1) with cementite portions (2), ferrite portions (3) and graphite flake portions (4), and graphite flake portions (4) on the honed surface (5) are exposed and ferrite components (3) are removed, preferably evaporated.

19. Cylinder or cylinder liner according to one of claims 16 to 18, wherein sharp-edged structures and / or edges of honing grooves (7) and / or protruding material tongues and / or edges of secondary grooves are rounded by melting.

20. Cylinder or cylinder liner according to one of claims 16 to 19, wherein graphite flake portions (4) are exposed on the honed surface (5) and a network of exposed graphite flakes is created which improves the tribological properties of the honed surface (5).

21. Cylinder or cylinder liner of a reciprocating piston engine, which has a honed surface (5) with honing grooves (7) and / or secondary grooves, wherein the honed surface (5) is treated by a method according to one of claims 1 to 15.

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