Solid-State Welded Nickel Alloys Without Base Metal Over-Aging

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Solution Overview

Problem

The existing heat treatment and stress relief processes for solid-state welded nickel alloys often result in over-aging of the base metal near the weld region, leading to a reduction in mechanical properties and increased susceptibility to strain age cracking due to multiple stabilization and aging processes.

Innovation Solution

A method involving a first heat treatment step on superalloy workpieces with a gamma matrix and gamma-prime precipitate phase, followed by solid-state joining and a post-weld stress relief operation, where the weld region is not initially stress-relieved, and a final aging heat treatment is applied to prevent over-aging of the base material regions adjacent to the heat-affected zone.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Stress or pressure

If a post-weld stress relief operation is performed on the weld region, then residual stresses are reduced, but the base material regions adjacent to the heat-affected zone undergo over-aging and strength reduction

Engineering Contradiction:

Improveresidual stressVSAvoidbase metal strength

Core Design Contradiction:

Stress or pressureVSStrength

Solution Approach 1:

The patent applies different heat treatment conditions to different regions of the welded structure. The weld region receives stress relief treatment while the base material regions adjacent to the heat-affected zone are protected from over-aging through controlled heating parameters, maintaining their strengthening precipitates and mechanical properties

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The heat treatment process is segmented into distinct zones: the weld region undergoes stress relief while the adjacent base material regions are excluded from the stress relief zone or subjected to different thermal parameters, allowing independent optimization of stress relief and strength retention in different areas

Inventive Principle:

Principle #1Segmentation

2Reliability

If multiple stabilization and aging processes are applied to the welded structure, then the material achieves proper heat treatment, but the base material near the weld region becomes over-aged and susceptible to strain age cracking

Engineering Contradiction:

Improveheat treatment completenessVSAvoidstrain age cracking susceptibility

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent performs stress relief on the weld region before applying the final aging treatment to the entire structure. This preliminary stress relief prevents the need for subsequent high-temperature treatments that would cause over-aging of the base material, thereby preventing strain age cracking susceptibility before it occurs

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

Instead of applying multiple stabilization and aging processes in the conventional sequence to the entire welded structure, the patent inverts the approach by first stress-relieving the weld region and then applying aging only to the base material regions, avoiding the harmful cumulative thermal exposure

Inventive Principle:

Principle #13The other way round (Inversion)

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 maintains comparable mechanical properties in the base material regions adjacent to the heat-affected zone, reducing the risk of over-aging and strain age cracking, thereby enhancing the structural integrity of welded components like rotor and bladed disk components for turbine engines.

Implementation Method 1

The first and second superalloy workpieces are joined using a solid state joining process

Methodology Applied

Scientific EffectDiffusion bonding: Diffusion Welding

Implementation Method 2

at least one of the first and second superalloy workpieces include a gamma matrix phase and a gamma-prime precipitate phase

Methodology Applied

Scientific EffectPrecipitation hardening: Precipitation Hardening

Implementation Method 3

subjected to a post-weld stress relief operation

Methodology Applied

Scientific EffectStress relaxation: Stress Relaxation

Data Source

PatentUS11826849B2Heat treatment and stress relief for solid-state welded nickel alloys

Publication Date: 2023.11.28 RTX CORP

AI summary

A joining method includes performing a first heat treatment step on a first superalloy workpiece and a second superalloy workpiece wherein at least one of the first and second superalloy workpieces include a gamma matrix phase and a gamma-prime precipitate phase. The first and second superalloy workpieces are joined using a solid state joining process, subjected to a post-weld stress relief operation and a final aging heat treatment.