MA-PVD CoCr Coated Titanium Implant Wear Resistance
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Solution Overview
Problem
Existing CoCr coatings on orthopedic implants, particularly those using magnetron sputtering physical vapor deposition (MS-PVD), exhibit high wear rates, delamination, and poor bond strength, making them less effective than conventional bulk CoCr surfaces, and fail to provide enhanced functionality.
Innovation Solution
A CoCr thin film is produced on a titanium shell using multi-arc physical vapor deposition (MA-PVD), resulting in a dense coating with a high percentage of hexagonal close-packed (HCP) phase and vertical grain orientation, providing superior hardness and wear resistance, and strong interface bonding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If magnetron sputtering physical vapor deposition (MS-PVD) is used to apply CoCr coating, then the coating process is approved and biocompatible, but the coating exhibits high wear rates, delamination, and poor bond strength
Solution Approach 1:
The patent changes the deposition parameters by using multi-arc PVD instead of magnetron sputtering, operating at different pressures (0.001-0.01 torr) and applying multiple arcs sequentially to build coating layers with controlled composition and microstructure, resulting in improved bond strength and reduced wear
Solution Approach 2:
The patent creates a composite coating structure with multiple layers of different compositions (CoCr, CoMo, CrMo) deposited in sequence, where each layer serves a specific function: early layers provide bonding to substrate, later layers provide wear resistance, achieving both high bond strength and low wear rate
2Object-affected harmful factors
If CoCr coating is applied to minimize defects of cast CoCr bearing surface, then wear is reduced, but the coating shows scratching, cracking, peeling and tribocorrosion after testing
Solution Approach 1:
The patent applies preliminary surface preparation to the titanium substrate including blasting and chemical etching before coating deposition, creating a mechanically and chemically activated surface that ensures strong bonding and prevents coating delamination and cracking during subsequent wear testing
Solution Approach 2:
The patent uses a composite coating system where initial layers are applied to bond to the prepared substrate, followed by intermediate layers, and finished with a wear-resistant CoCr layer, creating a gradient structure that prevents cracking and peeling while maintaining wear protection
3Strength
If MS-PVD CoCr coating is applied on CoCr substrate, then wear resistance is provided, but the coating hardness varies significantly (51.2-61.8 HRC) and shows non-uniform properties
Solution Approach 1:
The patent divides the coating application into multiple sequential deposition steps with different arc configurations and parameters, depositing distinct layers (CoCr bonding layer, CoMo intermediate layer, CrMo transition layer, CoCr wear layer) to achieve uniform composition and controlled hardness throughout the coating thickness
Solution Approach 2:
The patent systematically varies deposition parameters including arc number, power level, substrate temperature, and chamber pressure during each layer deposition to control the microstructure and hardness of each layer, achieving overall uniform properties while maintaining wear resistance
4Ease of manufacture
If existing Ti shell with thin film CoCr coating is used, then FDA approval and ease of machining are achieved, but the coating lacks enhanced functionality and shows poor performance in wear testing
Solution Approach 1:
The patent extends the coating thickness from thin film to thick coating (50-200 micrometers) using multi-arc PVD, maintaining the ease of machining the titanium substrate while building a thick, multi-layer coating that provides superior wear resistance and functional performance
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 MA-PVD CoCr coating demonstrates increased hardness, reduced scratch depth, and improved wear resistance compared to conventional CoCr surfaces, with a polished finish and high bond strength that maintains performance in simulated body fluid, effectively addressing the limitations of previous coatings.
Implementation Method 1
A CoCr thin film is produced on a titanium shell using multi-arc physical vapor deposition (MA-PVD)
Data Source
AI summary
A method for coating an orthopedic implant made of a titanium or titanium alloy substrate with a cobalt-chrome molybdenum alloy uses multi-arc physical vapor deposition (MA-PVD). The substrate has a first bearing surface coated with a coating made of the deposited cobalt-chromium molybdenum alloy. The bearing surface slidably receives a second bearing surface of the prosthetic joint component. The MA-PVD cobalt-chromium molybdenum alloy coating forming the first bearing surface is made up of hexagonal close packed (HCP) grains having a columnar structure with a length of about 1 μm and a width of about 0.1 μm with the length of each HCP grains being oriented generally perpendicular to the titanium substrate bearing surface.