Bilayer Chromium Nitride Coating for Reflectivity and Crack Resistance

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Solution Overview

Problem

Current chromium-containing coatings lack enhanced performance characteristics such as reflectivity and crack resistance, and often involve hazardous materials in their production.

Innovation Solution

A bilayer chromium nitride coating is formed over a substrate, comprising a first stoichiometric chromium nitride layer with uniform composition and a second layer with a progressively increasing chromium concentration and decreasing nitrogen concentration, achieved through reactive magnetron sputtering, which mimics the appearance and performance of electroplated chromium without using hazardous materials.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a single-layer chromium containing coating is used, then the coating process is simple, but the reflectivity and crack resistance are insufficient

Engineering Contradiction:

Improvecrack resistanceVSAvoidcoating structure

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The coating is divided into two distinct layers: a first chromium nitride layer providing crack resistance and a second chromium-rich layer providing reflectivity. This segmentation allows each layer to be optimized for its specific function, resolving the contradiction between reliability and structural simplicity.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The invention uses a composite coating structure with two layers of different compositions - the first layer is stoichiometric chromium nitride (CrN) for crack resistance, while the second layer is chromium-rich with lower nitrogen content for reflectivity. This composite approach enables both crack resistance and high reflectivity to be achieved simultaneously.

Inventive Principle:

Principle #40Composite materials

2Illumination intensity

If electroplated chromium is used to achieve high reflectivity, then the reflectivity is sufficient, but hazardous materials are involved in production

Engineering Contradiction:

ImprovereflectivityVSAvoidhazardous materials

Core Design Contradiction:

Illumination intensityVSObject-affected harmful factors

Solution Approach 1:

The invention replaces hazardous electroplating processes with a PVD (physical vapor deposition) process that uses chromium targets and nitrogen gas. This converts a harmful wet chemical process into a clean vacuum-based process, eliminating hazardous waste while maintaining the desired chromium-based reflective properties.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

Solution Approach 2:

The invention replaces the electrochemical deposition mechanism with a physical vapor deposition mechanism. Instead of using electrical current to deposit chromium from solution (electroplating), the process uses physical sputtering of chromium targets in a vacuum environment, eliminating the need for hazardous chemicals and waste treatment.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Reliability

If a bilayer chromium nitride coating is formed with graded composition, then reflectivity and crack resistance are improved, but the manufacturing process becomes more complex

Engineering Contradiction:

ImprovereflectivityVSAvoidcoating process

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The invention introduces dynamic control of gas flow rates during the PVD process to achieve the desired composition gradient. By dynamically adjusting the nitrogen gas flow rate - higher for the first layer and lower for the second layer - the process creates the optimal composition profile for both crack resistance and reflectivity without requiring complex post-processing.

Inventive Principle:

Principle #15Dynamics

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 bilayer chromium nitride coating provides superior reflectivity and resistance to cracking, while being environmentally friendly and cost-effective, eliminating the need for additional paint layers and using commercially available vacuum coating systems.

Implementation Method 1

reactive magnetron sputtering

Methodology Applied

Scientific EffectSputtering: Sputtering

Implementation Method 2

achieved through reactive magnetron sputtering

Methodology Applied

Scientific EffectPhysical Vapour Deposition: Physical Vapour Deposition

Data Source

PatentEP2920337B1Bilayer chromium nitride coated articles and related methods

Publication Date: 2019.01.16 VERGASON TECHNOLOGY INC

Figure 1

AI summary

A method for forming a chromium nitride coating over a substrate to provide a chromium nitride coated article, and the resulting chromium nitride coated article, each use a bilayer chromium nitride containing material layer. The bilayer chromium nitride containing material layer includes: (1) a first chromium nitride material layer having a first thickness, a first uniform chromium concentration and a first uniform nitrogen concentration located and formed closer to a substrate which provides the article; and (2) a second chromium nitride material layer having a second thickness, a second increasingly graded chromium concentration and a second decreasingly graded nitrogen concentration located and formed upon the first chromium nitride material layer. This particular bilayer chromium nitride containing material layer provides the article with superior reflectivity and crack resistance.