Cylinder Bore Prespray Processing for Thermal Spray Adhesion

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Solution Overview

Problem

Conventional prespray processing methods for thermal spray coatings on cylinder bore surfaces of aluminum cylinder blocks do not adequately roughen the inner grooves, leading to insufficient adhesion of the coating.

Innovation Solution

A prespray processing method that uses a combination of a tool bit and a wire electrode for electrical discharge machining to form spiral groove parts and finely roughened portions on the inner surface of the cylinder bore, enhancing the surface roughness and adhesion of the thermal spray coating.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional prespray processing is used to roughen the surface by boring, then the ridge parts are formed with broken surfaces, but the groove parts are not finely roughened resulting in insufficient adhesion

Engineering Contradiction:

Improveadhesion of thermal spray coatingVSAvoidsurface roughness of groove parts

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

The surface treatment is divided into two distinct segments: ridge parts receive broken surface treatment through boring, while groove parts receive finely roughened treatment through electrical discharge machining. This segmentation allows each region to have the optimal surface characteristics for maximum coating adhesion.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different surface qualities are applied to different locations on the cylinder bore surface. The ridge parts maintain a coarser broken surface texture, while the groove parts are transformed into finely roughened surfaces through electrical discharge machining, creating locally optimized adhesion characteristics throughout the surface.

Inventive Principle:

Principle #3Local quality

2Reliability

If only ridge parts are roughened with broken surfaces, then processing is simplified, but adhesion is insufficient because groove parts remain smooth

Engineering Contradiction:

Improveadhesion of thermal spray coatingVSAvoidprocessing method complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

Two different machining processes are merged into a single integrated treatment sequence: boring for ridge part roughening followed by electrical discharge machining for groove part finishing. This combination ensures comprehensive surface preparation across all surface features while maintaining a systematic and efficient processing flow.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The boring process is performed first to create the basic spiral groove structure and roughen the ridge parts. Subsequently, the electrical discharge machining is applied to further refine the groove parts. This preliminary action sequence ensures that each process builds upon the previous one to achieve the final desired surface characteristics.

Inventive Principle:

Principle #10Preliminary action

3Strength

If conventional boring processing is used, then the surface is roughened with spiral grooves, but the overall adhesion strength is limited due to insufficient groove part roughening

Engineering Contradiction:

Improvestrength of thermal spray coatingVSAvoidfineness of surface roughness

Core Design Contradiction:

StrengthVSManufacturing precision

Solution Approach 1:

The conventional purely mechanical boring process is supplemented with electrical discharge machining, which uses electrical energy to erode and roughen the groove parts. This substitution of mechanical action with electrical energy enables precise control over the fineness of surface roughness in the groove regions, achieving superior adhesion strength.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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

The method significantly improves the adhesion of the thermal spray coating by creating finely roughened portions on both the groove parts and ridge parts, reducing the risk of detachment and enhancing the strength of the coating, while also reducing the usage of thermal spray material and improving engine performance.

Implementation Method 1

a wire electrode is used for the purpose of forming finely roughened portions on the groove parts

Methodology Applied

Scientific EffectElectrical discharge machining: Electrical Discharge Machining

Implementation Method 2

the inner surface of the cylinder bore needs to be roughened in prespray processing for the purpose of enhancing adhesion of the thermal spray coating

Methodology Applied

Scientific EffectAdhesion: Adhesive

Data Source

PatentEP2444512B1Thermal spraying preprocessing method

Publication Date: 2020.08.19 NISSAN MOTOR CO LTD

Figure 1(a)~1(b)
Figure 2
Figure 3~4

AI summary

A boring cutter body (5) is inserted into a circular hole (3) and is rotated and moved in an axial direction, whereby screw-shaped groove parts (11) are formed by using a tool bit (9) provided on a tip end of an outer peripheral portion, and broken surfaces (15) are formed by breaking tips of ridge parts generated by formation of the groove parts (11). Moreover, the groove parts (11) are processed through electric discharge machining using a wire electrode (17) provided to the boring cutter body (5) behind the tool bit (9) in the rotating direction, thereby forming finely roughened portions (41) having more finely roughened shapes than the broken surfaces (15).