Nitrogen-Doped Tungsten Carbide Friction Coating Above 200°C

Solution Overview

Problem

Current friction-reducing coatings for high-temperature lubricated contacts, such as DLC and chromium nitride, face issues with wear and oxidation, leading to increased friction losses and design complexities in maintaining effective lubrication, especially at temperatures above 200°C.

Innovation Solution

A friction piece with a tungsten carbide coating doped with nitrogen (WC(N)) is developed, which provides enhanced thermal stability and oxidation resistance, reducing friction and wear while maintaining low surface roughness, even at high temperatures.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of energy

If DLC coating is used to reduce friction, then friction is reduced in mixed lubrication regime, but wear increases rapidly at temperatures above 200°C due to oxidation

Engineering Contradiction:

Improvefriction lossVSAvoidwear resistance at high temperature

Core Design Contradiction:

Loss of energyVSReliability

Solution Approach 1:

The invention changes the chemical composition parameters of the coating by doping tungsten carbide with nitrogen (5-12 atomic ratio %), which fundamentally alters the coating's oxidation resistance while maintaining low friction properties. This compositional parameter change enables the coating to withstand temperatures above 200°C without rapid oxidation-induced wear.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The invention creates a composite coating material by combining tungsten carbide (WC) with nitrogen doping, forming a new material system WC(N) that exhibits both low friction characteristics and high temperature stability. This composite approach merges the beneficial properties of WC (hardness, low friction) with nitrogen's oxidation resistance.

Inventive Principle:

Principle #40Composite materials

2Temperature

If chromium nitride coating is used to withstand high temperature, then thermal stability is improved, but friction reduction capability is reduced compared to DLC

Engineering Contradiction:

Improvethermal stabilityVSAvoidfriction loss

Core Design Contradiction:

TemperatureVSLoss of energy

Solution Approach 1:

The invention creates a composite coating material by combining tungsten carbide (WC) with nitrogen doping, forming a new material system WC(N) that exhibits both low friction characteristics and high temperature stability. This composite approach merges the beneficial properties of WC (hardness, low friction) with nitrogen's oxidation resistance.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The invention changes the chemical composition parameters of the coating by doping tungsten carbide with nitrogen (5-12 atomic ratio %), which fundamentally alters the coating's oxidation resistance while maintaining low friction properties. This compositional parameter change enables the coating to withstand temperatures above 200°C without rapid oxidation-induced wear.

Inventive Principle:

Principle #35Parameter changes

3Reliability

If lubricant flow rate is increased to improve heat dissipation and protection, then lubrication effectiveness is improved, but energy consumption increases

Engineering Contradiction:

Improvelubrication effectivenessVSAvoidenergy for lubricant circulation

Core Design Contradiction:

ReliabilityVSUse of energy by moving object

Solution Approach 1:

The nitrogen-doped tungsten carbide coating provides self-protection against oxidation and wear through its inherent chemical stability at high temperatures. The coating's nitrogen content creates a protective surface layer that resists oxidation without requiring additional lubricant flow, enabling the system to maintain effective lubrication with standard lubricant circulation rates.

Inventive Principle:

Principle #25Self-service

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 tungsten carbide coating with nitrogen significantly reduces friction and wear in lubricated mediums, outperforming traditional DLC and chromium nitride coatings by maintaining effectiveness in mixed lubrication regimes and withstanding high load temperatures without significant oxidation degradation.

Implementation Method 1

enabling a reduction in friction in a lubricated medium

Methodology Applied

Scientific EffectFriction reduction: Friction

Implementation Method 2

improving the resistance thereof to high load temperatures, especially above 200° C.

Methodology Applied

Scientific EffectOxidation resistance: Oxidation

Implementation Method 3

maintaining low surface roughness, even at high temperatures

Methodology Applied

Scientific EffectSurface roughness stability:

Data Source

PatentUS11236861B2Friction piece, mechanical system comprising such a friction piece and method of implementation

Publication Date: 2022.02.01 H E F

AI summary

The present invention concerns a friction piece (10) suitable for operating in a lubricated medium at a temperature higher than 200° C. The piece (10) comprises a metal surface (12) and an external coating (14) composed of tungsten carbide doped with nitrogen WC(N) with an atomic ratio of nitrogen between 5 and 12%. The invention also relates to a mechanical system (1) comprising such a piece (10). The invention also relates to a method for implementing such a piece (10).