Cylinder Block Surface Roughening for Thermal Spray Adhesion
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Solution Overview
Problem
Conventional thermal spraying methods for forming a rough surface on the internal surface of a cylinder block, such as shot blast and cutting tool methods, often result in residue and insufficient adhesiveness of the thermal spray coating, leading to reduced reliability due to incomplete surface roughening and weak bonding.
Innovation Solution
A thermal preprocessing method using a processing roller with an uneven outer surface, made of sintered hard alloy, is employed to roughen the internal surface of the cylinder block by rotating and pressing it against the surface, ensuring a net-like roughness that prevents residue and enhances adhesiveness by attaching nickel material for improved bonding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If shot blast process is used to form rough surface, then adhesiveness is increased, but blast particle residue remains on surface reducing reliability
Solution Approach 1:
The harmful blast particles are removed from the surface through a cleaning step (washing with water or organic solvent) before thermal spraying. This extraction of the harmful element allows the beneficial rough surface structure to remain while eliminating the residue that would compromise coating reliability.
Solution Approach 2:
The surface is roughened by shot blasting in advance before thermal spraying, creating the anchor effect needed for good adhesiveness. The preliminary roughening action prepares the surface optimally for coating, and subsequent cleaning removes only the loose particles while preserving the embedded roughness structure.
2Reliability
If cutting tool method is used to form spiral grooves, then rough surface is formed, but adhesiveness is weak against forces in direction of grooves
Solution Approach 1:
Instead of using cutting tools that create spiral grooves (which weaken the surface in the groove direction), the invention uses shot blasting that creates a random, multi-directional rough surface structure. This inverts the approach from mechanical cutting to impact-based roughening, producing a surface that resists forces from all directions rather than being weak along groove paths.
3Reliability
If conventional pre-thermal spray process with flux coating is used, then adhesiveness is increased, but processing time and capital investment increase
Solution Approach 1:
The complex multi-step pre-thermal spray process (flux coating, dehydration heating, bond-coating) is extracted and replaced with a single shot blasting roughening step followed directly by thermal spraying. This removes unnecessary intermediate steps while maintaining or improving adhesiveness through the anchor effect of the rough surface.
Solution Approach 2:
The surface preparation approach changes from chemical/thermal treatment (flux coating and heating) to mechanical impact treatment (shot blasting). This parameter change in the preparation method achieves comparable or better adhesiveness with significantly reduced processing time and equipment requirements.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This method effectively increases the adhesiveness of the thermal spray coating by creating a finer and more stable rough surface, reducing processing time, and extending tool life compared to traditional methods, while ensuring reliable bonding and improved productivity.
Implementation Method 1
the inner surface is sufficiently roughened so as to have an uneven shape on the internal surface of the cylinder by pressing of a processing roller having unevenness on its external periphery surface while it rotates and moves
Implementation Method 2
applying nickel material to the uneven outer surface of the processing roller, and thereafter, bringing the outer surface in contact with the cylinder internal surface, and rotating the processing roller relative to the cylinder internal surface while pressing against the cylinder internal surface to roughen, and at the same time, detaching at least some of the nickel material from the uneven outer surface and attaching at least a portion of the detached nickel material to the cylinder internal surface
Data Source
AI summary
The adhesiveness of a thermal spray coating and a cylinder internal surface is improved by forming a sufficient roughened surface on an internal surface. A processing roller is installed on the main shaft of a processing device via a pressurizing mechanism. An uneven surface is provided on the external periphery of the processing roller. By pressing the processing roller against the internal surface while the roller rotates and moves, a fine unevenness that corresponds to the unevenness of the roller is formed on the cylinder internal surface. A thermal spray coating is formed on the internal surface where the inner surface has been roughened by forming the above-mentioned unevenness.