Thermal Sprayed Lap Joints for Unweldable Material Pairs

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Solution Overview

Problem

Current technologies lack a reliable thermal welding method for joining dissimilar materials in multi-material designs, particularly those involving non-weldable combinations like metals with glass, wood, or fiber composites, often resulting in issues such as hot cracks, liquid metal embrittlement, and microstructure damage during welding.

Innovation Solution

Applying a metallic thermal sprayed layer with defined thickness and surface roughness on the non-weldable material, followed by a welding process that only joins the sprayed layer with the metallic material, thereby avoiding direct welding of the unweldable material and controlling temperature to prevent damage.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If direct welding is applied to dissimilar material combinations (metal with glass, wood, or fiber composites), then joining is achieved, but hot cracks, liquid metal embrittlement, and microstructure damage occur

Engineering Contradiction:

Improvejoint strengthVSAvoidweld quality

Core Design Contradiction:

StrengthVSReliability

Solution Approach 1:

A metallic thermal sprayed layer is applied as an intermediary between the non-weldable material (glass, wood, fiber composite) and the metallic material to be welded. This intermediate layer acts as a buffer that protects the non-weldable material from direct thermal exposure during welding, preventing hot cracks, liquid metal embrittlement, and microstructure damage while still enabling reliable joining of the metallic components.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The metallic thermal sprayed layer is applied in advance before the welding process. This preliminary action prepares the surface of the non-weldable material with a thermally conductive metallic coating that will protect it during subsequent welding operations, enabling the welding process to proceed without damaging the non-weldable material.

Inventive Principle:

Principle #10Preliminary action

2Ease of manufacture

If thermal sprayed layer is applied on non-weldable material, then weldability is improved, but process complexity increases with two-step sequence

Engineering Contradiction:

ImproveweldabilityVSAvoidprocess steps

Core Design Contradiction:

Ease of manufactureVSDevice complexity

Solution Approach 1:

The thermal spraying process utilizes the substrate's own surface characteristics to achieve effective coating adhesion. The process is self-contained, requiring only standard thermal spraying equipment and materials, without needing additional complex preparation or specialized tooling for the specific non-weldable material type.

Inventive Principle:

Principle #25Self-service

3Temperature

If thermal sprayed layer is applied on sandwich structure, then polymer core is protected from overheating, but manufacturing time increases

Engineering Contradiction:

Improvepolymer core temperatureVSAvoidmanufacturing cycle time

Core Design Contradiction:

TemperatureVSLoss of time

Solution Approach 1:

The metallic thermal sprayed layer is applied in advance on the polymer core of the sandwich structure before the welding process. This preliminary protective coating acts as a thermal buffer during subsequent welding operations, preventing the polymer core from overheating while enabling faster welding parameters to be used, ultimately reducing total manufacturing cycle time.

Inventive Principle:

Principle #10Preliminary action

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

Enables successful welding of previously unweldable material combinations by acting as a thermal buffer, reducing the risk of hot cracks, liquid metal embrittlement, and microstructure damage, while improving weld quality and preventing corrosion and embrittlement.

Implementation Method 1

a metallic thermal sprayed layer is applied on the surface of the non-weldable material... which will work during the following actual welding process as a thermal buffer

Methodology Applied

Scientific EffectThermal conduction: Conduction (thermal)

Implementation Method 2

a metallic thermal sprayed layer is applied on the surface of the non-weldable material... with a well-defined thickness, surface roughness and transition resistance

Methodology Applied

Scientific EffectThermal insulation: Thermal Insulation

Data Source

PatentUS11524351B2Multistage joining process with thermal sprayed layers

Publication Date: 2022.12.13 OUTOKUMPU OY

AI summary

Method for joining of at least two unweldable materials, non-weldable directly to each other with thermal joining processes in a lap joint configuration, where a two step sequence is used consisting of a first step to apply a thermomechanical or mechanical surface protection layer on the surface of an unweldable material and a second step, where a thermal joining process is used to joint the sprayed layer with an applied layer sheet.