Diffusion Welding Carbon Activity Control

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Solution Overview

Problem

Existing diffusion welding processes face challenges in joining materials with different carbon activities, leading to unwanted carbon diffusion that can reduce the surface hardness and wear resistance of mechanical components, particularly in rolling bearing applications.

Innovation Solution

A process involving a sheet metal element with carbon activity greater than or equal to the second material's carbon activity, ensuring no significant carbon diffusion occurs, and using hot isostatic pressing to join materials while creating a closed space for the second material, which can be in powder form, to prevent carbon loss and potentially enrich the surface with nitrogen.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If diffusion welding is used to join two materials with different carbon activities, then the materials can be joined together, but carbon will diffuse from the high carbon activity material to the low carbon activity material, reducing surface hardness and wear resistance

Engineering Contradiction:

Improvesurface hardnessVSAvoidcarbon loss

Core Design Contradiction:

StrengthVSLoss of substance

Solution Approach 1:

A sheet metal element with controlled carbon activity is introduced as an intermediary between the two materials being joined. This intermediary element acts as a carbon buffer, preventing direct carbon diffusion between the materials while still allowing them to be joined through diffusion welding. The sheet metal element's carbon activity is specifically controlled to be higher than or equal to the second material's carbon activity, ensuring carbon flows into the sheet metal rather than into the second material, thus preserving the second material's surface hardness and wear resistance.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If diffusion welding is performed without controlling carbon activity, then the joining process can be completed, but the surface properties of the second material deteriorate due to carbon diffusion

Engineering Contradiction:

Improvewear resistanceVSAvoiddiffusion welding control

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The carbon activity parameter of the sheet metal element is specifically controlled and adjusted to be higher than or equal to the carbon activity of the second material. This parameter control is achieved by selecting appropriate sheet metal compositions and processing conditions. By controlling this key parameter, the invention ensures that carbon diffusion occurs in the desired direction (into the sheet metal) rather than into the second material, thereby preserving the second material's wear resistance while simplifying the overall manufacturing control.

Inventive Principle:

Principle #35Parameter changes

3Stability of the object's composition

If a sheet metal element is introduced to control carbon diffusion, then carbon loss from the second material is prevented, but the device complexity increases

Engineering Contradiction:

Improvecarbon concentration stabilityVSAvoidprocess structure

Core Design Contradiction:

Stability of the object's compositionVSDevice complexity

Solution Approach 1:

The sheet metal element is designed to be homogeneous in composition and properties, making it a simple yet effective component. Rather than introducing a complex multi-layered or gradient structure, the invention uses a uniform sheet metal element with controlled carbon activity. This homogeneous design achieves carbon concentration stability in the second material while minimizing the increase in device complexity, as the sheet metal element is a straightforward component that can be easily integrated into the diffusion welding process.

Inventive Principle:

Principle #33Homogeneity

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 approach ensures improved diffusion welding by preventing carbon loss from the second material, maintaining its surface hardness and wear resistance, and potentially enhancing the mechanical component's properties through controlled carbon and nitrogen diffusion.

Implementation Method 1

the carbon activity of the second material Ca2 and the carbon activity of the sheet metal element Cam at the temperature of joining fulfills the relation Ca2≦Cam... no or essentially no carbon will be diffused from the second material to the sheet metal element

Methodology Applied

Scientific EffectCarbon diffusion: Diffusion

Implementation Method 2

joining the first and second material by means of diffusion welding

Methodology Applied

Scientific EffectDiffusion welding: Diffusion Welding

Implementation Method 3

using hot isostatic pressing to join materials

Methodology Applied

Scientific EffectHot isostatic pressing: Hot Isostatic Pressing

Data Source

PatentUS9555501B2Process for obtaining a mechanical component

Publication Date: 2017.01.31 AB SKF SKF PATENT DEPARTMENT

AI summary

A process for obtaining a mechanical component by joining a first metallic material and a second metallic material. The process comprises: (A) putting the first material and the second material in contact with each other, (B) fixating a sheet metal element onto the first material to at least partly enclosing the second material and so that the sheet metal element is at least partly in contact with the second material. The sheet metal element comprises carbon, joining the first material and the second material by diffusion welding. The carbon activity of the second material Ca2 and the carbon activity of the sheet metal element Cam at the temperature of joining fulfills a relation Ca2≦Cam.