Nitrogen Enriched Austenitic Iron Alloy via Hot Isostatic Pressing

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Solution Overview

Problem

The existing methods for adding nitrogen to austenitic iron alloys, such as nitriding at high temperatures, are inefficient and costly, requiring masking of non-target areas and affecting mechanical properties, while also limiting uniform nitrogen distribution.

Innovation Solution

A method involving placing austenitic iron alloy powder in a can, evacuating gases, supplying nitrogen, and hot isostatically pressing to diffuse nitrogen and produce a nitrogen-enriched austenitic iron alloy bar with specific compositions, utilizing a large surface area to volume ratio for uniform nitrogen distribution and consolidation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Quantity of substance

If nitrogen is added during casting using master alloy, then nitrogen content is increased, but nitrogen distribution is non-uniform and requires additional processing

Engineering Contradiction:

Improvenitrogen contentVSAvoidnitrogen distribution uniformity

Core Design Contradiction:

Quantity of substanceVSManufacturing precision

Solution Approach 1:

The patent applies preliminary action by pre-mixing nitrogen-containing powder with the austenitic iron alloy powder before the hot isostatic pressing process. This preliminary preparation ensures that nitrogen is already distributed throughout the powder mixture before consolidation, eliminating the need for subsequent nitrogen distribution adjustments and achieving uniform nitrogen content throughout the final product.

Inventive Principle:

Principle #10Preliminary action

2Strength

If nitriding is performed at high temperature, then nitrogen is added to improve strength and corrosion resistance, but mechanical properties are affected and masking is required

Engineering Contradiction:

Improvestrength and corrosion resistanceVSAvoidmasking requirements and process complexity

Core Design Contradiction:

StrengthVSDevice complexity

Solution Approach 1:

The patent merges the nitrogen addition process with the hot isostatic pressing consolidation process. By introducing nitrogen gas during HIPping, the nitrogen enrichment occurs simultaneously with powder consolidation, eliminating the need for separate nitriding operations and associated masking steps. This integration achieves both densification and uniform nitrogen distribution in a single process.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The patent changes the parameters of nitrogen addition by performing it at lower temperatures during HIPping rather than at high temperatures during conventional nitriding. This parameter change allows nitrogen to be incorporated during consolidation without the harmful effects of high-temperature nitriding, such as distortion and the need for masking, while still achieving the desired nitrogen content for improved strength and corrosion resistance.

Inventive Principle:

Principle #35Parameter changes

3Manufacturing precision

If powder metallurgy is used with HIPping, then dense components are produced, but nitrogen enrichment is insufficient without additional processing

Engineering Contradiction:

Improvedensity and consolidation qualityVSAvoidnitrogen content

Core Design Contradiction:

Manufacturing precisionVSQuantity of substance

Solution Approach 1:

The patent applies continuity of useful action by continuously introducing nitrogen gas during the hot isostatic pressing process. The nitrogen gas is supplied throughout the consolidation cycle, ensuring that nitrogen enrichment occurs continuously alongside powder densification. This simultaneous continuous action ensures both high density achievement and adequate nitrogen content in the final product without requiring separate processing steps.

Inventive Principle:

Principle #20Continuity of useful 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

This method achieves effective nitrogen enrichment with improved mechanical properties and uniform distribution, enhancing strength and corrosion resistance, and reducing stacking fault energy, suitable for manufacturing components or coatings, including those for nuclear reactors.

Implementation Method 1

hot isostatically pressing the austenitic iron alloy powder in the can to diffuse the nitrogen into the austenitic iron alloy powder

Methodology Applied

Scientific EffectDiffusion: Diffusion

Implementation Method 2

hot isostatically pressing the austenitic iron alloy powder in the can to diffuse the nitrogen into the austenitic iron alloy powder and to produce a nitrogen enriched austenitic iron alloy bar

Methodology Applied

Scientific EffectHot Isostatic Pressing: Hot Isostatic Pressing

Data Source

PatentUS11007571B2Method of manufacturing an austenitic iron alloy

Publication Date: 2021.05.18 ROLLS ROYCE PLC

AI summary

A method of manufacturing an austenitic iron alloy comprising placing austenitic iron alloy powder in a can, evacuating air and other gases from the can, supplying nitrogen gas into the can, sealing the can and then hot isostatically pressing the austenitic iron alloy powder in the can to diffuse the nitrogen into the austenitic iron alloy powder and to produce a nitrogen enriched austenitic iron alloy bar and removing the can from the nitrogen enriched austenitic iron alloy bar.