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OMTEC 2016 Coating Trends:
Hydroxyapatite Coatings
June 15, 2016 10 AM – 10:15 AM
Presenter: Dr. Parimal V. Bapat
Research Engineer Orchid Orthopedic Solutions
Outline
• Coatings on Medical implants • Plasma Sprayed HA Coatings: Process and Properties • Future of HA coatings • FDA regulatory hurdles
Bone
http://classes.midlandstech.edu/carterp/Courses/bio210/chap06/lecture1.html
Cells found in Bone
https://www.boundless.com/biology/the-musculoskeletal-system/bone/cell-types-in-bones/
Why do we need Orthopedic Implants
To replace diseased bone & joints • Arthritis, Osteoporosis, Cancer etc. • Trauma
http://www.sonoramedicalcenter.org/services-and-programs/understanding-hip-pain
Implants
• Implant materials: Ti and CoCr alloys, SS etc.
• Properties: Corrosion resistant, strength, rigidity, long fatigue life, biocompatibility etc.
Total Knee Replacement
Total Hip Replacement
Shoulder Replacement
Implant-tissue reaction
Implant–Tissue Reaction Consequence Toxic Tissue dies
Biologically nearly inert—smooth surface
Tissue forms a nonadherent capsule around the implant (no bonding with bone)
Biologically nearly inert—porous or threaded surface
Tissue grows into pores or threads (forms mechanical bond with bone)
Bioactive Tissue forms interfacial bond with implant (bioactive fixation)
Dissolution of implant Implant resorption and replacement with soft tissues or bone
http://tpx.sagepub.com/content/36/1/85
Bioactive Material: Hydroxyapatite (HA)
• Major inorganic component of bone ECM Ca10(PO4)6(OH)2 • High Osteoconductivity /Bioactivity • Crystal structure – Hexagonal • Insulator with band gap 5eV • Hardness - 5 on Mohs scale (Diamond is 10 on Mohs scale)
History of HA Coatings
1920 – The suggestion of use for calcium phosphate materials was first reported as a bone graft material 1973 – HA first used as a porous graft material
1980 – First plasma sprayed coating on a dental implant 1984 – First HA hip implants implanted in the U.S. 1990 – First FDA approval for HA on orthopedic implants
Plasma Sprayed Coating
Plasma Spray Process
http://www.sauerengineering.com/thermal_spray.htm
• High temperature Process ~ 10,000-15000 °C
• High velocity ~2000 m/s
Plasma Spray Coating
•Coating Adhesion Strength • Static Shear Strength • Shear Fatigue Strength
•Chemical Composition •Phase Composition
•Trace Elements
•Coating appearance
•Color of the coating
•Coating Topography
Coating Properties
Morphology Properties Chemical Properties Mechanical Properties
Mechanical Properties
Some of the important variables contributing to the mechanical integrity of the coating include: • Degree of melting • Substrate Surface preparation • Coating Thickness • Substrate material / mass
Plasma sprayed coatings consist of layers of ‘splatted’ particles
http://www.sauerengineering.com/thermal_spray.htm
Residual Thermal Stress
http://www.gordonengland.co.uk/tsc.htm
Over-melting – deliberate over melting has the intention of greater adhesion and more efficient deposition – this leads to cracking and compromised dissolution / mechanical behavior
Degree of Melting
a b
Under-melting – deliberate under melting has the intention of preserving the original characteristics of the
powder – this leads to porosity and compromised dissolution / mechanical behavior
Degree of Melting
• Temperature of the plasma
• Arc gas • Powder flow • Gun Configuration
Surface Preparation
Roughened surface
Machined surface
Plasma sprayed HA coatings must ideally be applied to a grit blasted roughened surface which provides more surface area for adhesion
• Grit composition – Al2O3
• Mesh size • Pressure • Substrate hardness • Nozzle geometry
Coating Thickness
a b
Optimal Coating thickness < 100 µm
• Powder flow • Melting • Spray distance
Substrate Material
• Differences in substrate material and mass can lead to varying levels of adhesion and can affect the chemical make-up of the coating.
• Residual stresses in the coating and how the coating cools is critical for final coating properties.
• Damage due to the blast procedure • Damage due to heating – Oxidation, discoloration etc.
15% Reduction in fatigue strength for Titanium substrate.
CoCr and Stainless Steel are less affected
Chemical Properties
Some of the important variables contributing to the Chemical composition of the coating include: • Starting powder • Phase composition of the coating
Powder
• Purity of the powder – Is powder ~ 100% crystalline HA? Starting powder can be 100% crystalline but resultant
product ends up as something else once plasma sprayed
• Phase composition of the powder – what are the predominant phases within the powder? Is powder predominantly HA? Or is made up of some other
phases?
• Particle size distribution – What is the average particle size?
Phase Composition of the Coating • Melting Point of HA ~ 1250°C
Pure ~ 100% HA powder Ca10(PO4)6(OH)2
Calcium Oxide CaO
Tetra Calcium Phosphate Ca4(PO4)2O
α- TCP and β- TCP Ca3(PO4)2
Amorphous phases
CaO > amorphous > TTCP > α-TCP > OHA > ß-TCP > HA
• Dissolution Behavior
Some of the Important Variables Contributing to HA Decomposition
• Powder type/morphology • Powder gas pressure • Gases used – type, purity • Gun configuration – powder injection, velocity/dwell time • Distance
Spherical Particles
a b
Irregular Particles
Coating Morphology
a
e d c
b
FDA Guidelines for HA Coatings
Early HA coatings were not controlled, and had varying degrees of porosity, amorphous phase content and adhesion. This lead to varying degrees of success with HA in orthopedics. Other factors such as patient selection, implant design, surgical expertise etc. play a role as well.
In 1992, the FDA Published Guidelines for HA Coatings Including Mandatory Tests like:
Chemical Properties Elemental analysis – powder and coating Ca/P ratio – powder and coating Density – powder and coating XRD – powder and coating Infrared Spectroscopy Solubility & Dissolution Mechanical Properties Abrasion resistance Tensile strength Shear strength Fatigue strength Morphology Thickness Roughness
FDA Guidance Document Acceptance Criteria:
Chemical Tests • Powder – minimum 95% HA • Crystallinity of Coating – minimum 62% • IR – identification of (PO4)3 and (OH)-1 • Trace Elemental analysis – Cd, Hg, Pb, As < 50ppm • Ca/P ratio, powder – 1.66 – 1.67 • Ca/P ratio, coating – 1.67 – 1.76 • Density, powder – 3.05 g/cm3, min • Density, coating – 2.98 g/cm3, min Mechanical Tests • Tensile strength – 7400 psi, min • Shear strength – 3198 psi, min
Future of HA Coatings
Driving factors for exploring new techniques for HA coatings are:
Plasma Sprayed HA Coating Limitations – High temperature process – Coats only visible area – Is osteoconductive but not osteoinductive
Cost of coating implants Functionality of the Coatings
HA Coating Techniques
Physical Vapor deposition
Sol-gel
HA Coating Techniques
Electrostatic Spray Deposition
Electrophoretic Deposition
Dip Coating
• Coats 3D porous structures
• Low processing temperature
• Relatively cheap • Very thin Coatings
• Uniform Coating on flat surfaces
• Relatively cheap
• Inexpensive • Quick processing time • Coats 3D structures
• Uniform Coating • High deposition rates • Coats 3D structures
• Great Control over coating thickness
• Great control over chemical composition
• Processing in controlled atmosphere
• Limited Coating thickness can be achieved
• Only coats visible areas
• Fragile
• High sintering temperature
• Fragile
• High sintering temperature
• Crack within the coating
• Coats visible area • Expensive and
time consuming
FDA Regulatory Hurdles for new Coating Techniques
• No set guidelines available for new coatings. • Have to compare data with existing plasma spray coating
guidelines. • FDA relies on ASTM up to certain extent for developing test
methods which can take anywhere from 6 – 18 months to get approved.
Orchid
Orchid Master
File FDA
OEM
confidential
OMTEC, Chicago, June 15, 2016
Dr. Antonio Santana, Head Segment Medical at IHI Ionbond
MedthinTM 65 Ti
confidential
Medthin™
2
Medthin™ biocompatible coatingsIon release reduction
DLC and AlTiN for Color Coding andAnti-Reflection
Wear protection
Hard coatings
ISO 13485, 10 coating centers globally
Development of new technologies andcoatings such as HIPIMS SiN in LifeLongJoints LLJ
confidential
PVD Titanium “TST”
Ionbond promoted in the past 5-10 microns thickness “TST” as alternative to
VPS on metal implants for cell attachment and cell on growth
Application of TST on metals find high competition:
VPS gives >>50µm “porous” coatings
a certain “establishment” of thick VPS
TST Process:
PVD coating from Titanium grade II
ASTM F67 sources F
Cell attachment onto TST
confidential
From Metal to PEEK – VPS technology - Risks
Out in the market, VPS is offered to coat Ti on PEEK
Strong modifications of the VPS process had to be done to coat PEEK:
“cut in heat transfer” leads to a certain risk of coating adhesion loss.
Adhesion issues were compensated with PEEK surface blasting (roughening), Still missing in VPS tech an “in situ” chemical modification on the PEEK surface
“Low energy VPS” PLUS “high Ti coating thickness” leads to stress and potential cohesion and adhesion issues.
4
Thick coatings have cohesion and adhesion issues
confidential
From Metal to PEEK – Ionbond proposal
The Ionbond TST process was also adapted to coat PEEK and PEKK
Introduction of the Plasma Activation for PEEK and PEKK• Improved chemical bonding: Atoms with high affinity have been privileged to
form the interface compound• Improvement of electrical conductivity of the interface
Remain with a PVD Titanium “TST” process as the main coating layer• It can be 200 nanometers up to 20 micrometers
The MedthinTM 65 Ti is born!
5
confidential
MedthinTM 65 Ti- Process Impact on PEEK
PEEK crystallinity was checked before and after MedthinTM 65 Ti
Differential Scanning Calorimetry DSCFourrier Transform Infrared Spectroscopy, FTIRGel permeation chromatography GPC
6
confidential
MedthinTM 65 Ti on PEEK – DSC analysis
In black no coating (reference)
In red pre blasted and coated
In blue only coated7
confidential
MedthinTM 65 Ti on PEEK – FTIR analysis
Blasted and coated with Medthin 65 Ti
8
Coated with Medthin 65 Ti
confidential
MedthinTM 65 Ti on PEEK – Structure
Polydispersity is similar for uncoated and coated substrate (with and without preblasting)
The crystallinity levels (DSC) are consistent with injection molded parts
The FTIR spectra of coatings have are comparable with the FTIR trace of the Invibio PEEK Optima
Ionbond to thank Invibio for providing these measurements
9
confidential
Scanning Electron Micrographs
Showing the coating roughness and morphologySome heterogeneity (porosity) was noticed at high magnification
10
MedthinTM 65 Ti on PEEK – Morphology
10µm
MedthinTM 65 with 5 µm thickness
confidential
Coating cross section prepared by focused ion beam (FIB)
No destruction of the cross section features of the coating
11
Medthin 65 Ti on PEEK- Structure analysis
confidential
Coating Thickness Distribution
12
Cross section prepared by FIB
Titanium droplets appeared well glued to the overall coating
Cross section prepared by polished cross section
Appropriate for thickness measurement
Medthin 65 Ti on PEEK- Structure analysis
confidential
MedthinTM 65 Ti – Process Features
13
MedthinTM 65 Ti
Materials PEEK and PEKK
Surface monitoring preparation/condition
• Al2O3 blasted• Injected molded• Machined surface
Cleaning of Residues Organic and Impurities
Applied Surface Modification of Substrate
Modified by plasma conditions for enrichment of O bonds on
the surface
Coating Below 140°CHigh Energy low deposition
rate
confidential
MedthinTM 65 Ti – Coating Features
ASTM F 1147-05 - Tension testing of calcium phosphate and metallic coatings
14
Coating MedthinTM 65 Ti
ChemistryFrom Ti targets gases used for coating
Titanium Grade IIASTM F67
Thickness Up to 20 microns
Structure*
SEM observationsSlightly Porous
Roughness*
ISO 4287 and 4288:1996Ra about 1 micron
Adhesion to substrate*
ASTM F 1147-05 >20MPa
* Nominal coating thickness5µm
confidential
MedthinTM 65 Ti – Adhesion F1147-5
15
confidential
MedthinTM 65 Ti - Adhesion ASTM D3359
Scratch and tape test used a lot for coatings on glass
We use D3359 to control production Q
Correlation with Adhesion F1147-5 was done
16
Overview of scratch grid
Overview of scratches over coating on blasted surface
Overview of scratches over coating on machined surface
confidential
Less than 1 minute blasting ok, blasting residues possible to remove prior to coating
17
Surface Preparation Prior to Coating
Machined surface (coated)
Blasted surface
Machined surface, or injected molded
confidential
Surface Preparation Prior to Coating
Avoid turned/machined surfaces
They are typically damaged Coating varies quite a lot on machines surfaces
Blasting is necessary on these machined surfaces
This does not mean that is always needed.
18
confidential
Unbeatable Coating Capacity
Capacity of hundreds of parts per run
Surface preparation to be seen case by case
The exact number of parts depends on the requirements-which spec we have to comply with
Ionbond specification target 5 microns nominal thickness
MedthinTM 65 is an effective and technically right way of coating PEEK and PEKK materials
19
confidential
Going Forward To do:
Static Shear Strength per ASTM F1044
Shear Fatigue Test per ASTM F1160
Abrasion Resistance per ASTM F1978
20
All of these above expected to be better than any VPS coating, due to:
High and constant adhesion on all type of surfaces, overall Medthin 65 coating properties, low thickness, high cohesion etc.
Delivery conditions of coated implants to be discussed as we do not have a clean room packaging today.
Advice from audience welcome
confidential
Contacts
21
Michael HelmesSales Manager, North [email protected]
IHI Ionbond, Inc.1823 E. Whitcomb AveMadison Heights, MIUSA
Phone +1 248 398 9100 Ext. 2227Cell Phone: + 1 949-375-6822
Or Dr. Antonio [email protected] Head Segment Medicalhttp://www.ionbond.com/en/coating-services/medical/
TECHMETALS
PVD Coatings in the Medical World
Jason Sikora, CEF Engineering Materials Director
PVD – what is it?
• Physical Vapor Deposition evaporates material in a high energy state rather than using ions in an aqueous bath.
• Vaporized metal ions are then drawn to the part surface and condensed.
• The process typically takes place either in a vacuum or controlled atmosphere.
Types of PVD
• Cathodic Arc: Utilizes an electric arc on the surface of the material to be deposited. Arc evaporates material in a very high energy state.
• Electron Beam: Uses electron beam to evaporate material in a moderate energy state
• Sputtering: Uses plasma bombardment to evaporate material in a moderate energy state
• Evaporation: Uses heat to evaporate material in a low energy state
Advantages
• Extremely high hardness (2500-3400 HV) • Low coefficient of friction • Good wear resistance • Low coating thickness (0.00008” typical) • Can be combined with each other or other coating technologies
for composite properties
Disadvantages
• Higher cost than standard electroplating processes
• Process is done at high temperature (~750 F)
• Limited part size (30” diameter x 30”)
• Low corrosion protection
• Line-of-site application, recesses and interior regions may not cover
• Not good in high point-loading applications (eggshell effect)
Good Substrates
• Steels (carbon, tool, specialty, stainless)
• Titanium
• Chromium plating
• Nickel Plating
• Inconel
• Carbides
Medium Substrates
Substrates that may require some additional or special processing:
• Aluminum
• Beryllium copper
Poor Substrates
• Plastics
• Non-conductive material
• Zinc or cadmium bearing alloys
• PTFE or silicon bearing material
• Surfaces with heavy scales or oxides from heat treating
Coating Properties
Coating Type Color Hardness (Hv)
Thickness (µm)
Coefficient of Friction
Max usage Temp (F)
DLC Black 2300-2500 1-5 0.1 750
TiN Gold 2300-2500 1-5 0.55 1100
TiCN Rose 3200-3600 1-5 0.2 750
CrN Silver 1800-2000 1-5 0.3 1300
AlTiN Black 3100-3300 1-5 0.7 1600
ZrN Pale Gold 1900-2100 1-4 0.4 1050
DLC (Diamond-Like Carbon)
Coating Type Color Hardness (Hv)
Thickness (µm)
Coefficient of Friction
Max usage Temp (F)
DLC Black 2300-2500 1-5 0.1 750
DLC combines high hardness with a very low coefficient of friction, making it ideal for wear applications. The dark appearance of DLC resists autoclave cycling better than AlTiN coatings, which will start to lighten over time. DLC also has the advantage of being able to be applied to aluminum components. DLC is not as widely used in the medical industry as it could be, once more design engineers become more comfortable with it. Primary use right now is surgical instruments.
TiN (Titanium Nitride)
text
Coating Type Color Hardness (Hv)
Thickness (µm)
Coefficient of Friction
Max usage Temp (F)
TiN Gold 2300-2500 1-5 0.55 1100
Very common in the medical industry. Titanium nitride has good hardness, decent maximum temperature use, distinct appearance, and serves as a good all-purpose PVD coating. The gold color of TiN is much deeper and richer in hue than that of the ZrN. Titanium nitride is used in both instruments and implant components.
TiCN (Titanium Carbo-Nitride)
text
Coating Type Color Hardness (Hv)
Thickness (µm)
Coefficient of Friction
Max usage Temp (F)
TiCN Rose 3200-3600 1-5 0.2 750
Titanium Carbo-Nitride is less commonly used in the medical industry but has excellent wear properties, combining an extremely high hardness with a very low coefficient of friction. Titanium Carbo-Nitride is also useful on stainless steel components as its characteristic rose color gives an additional option on stainless steel components where rapid identification or contrasting demarcations are important. Current use in the medical industry is fairly rare.
CrN (Chromium Nitride)
text
Coating Type Color Hardness (Hv)
Thickness (µm)
Coefficient of Friction
Max usage Temp (F)
CrN Silver 1800-2000 1-5 0.3 1300
Chromium Nitride’s advantage over many of the other PVD coatings is its ductility. The appearance of chromium nitride is very similar to that of a chromium plated component, but the chromium nitride is harder and has a higher coefficient of friction than chromium plating has. CrN is most often seen called out on implant components.
AlTiN (Aluminum Titanium Nitride)
text
Coating Type Color Hardness (Hv)
Thickness (µm)
Coefficient of Friction
Max usage Temp (F)
AlTiN Black 3100-3300 1-5 0.7 1600
Aluminum titanium nitride is an excellent choice for any type of cutting, drilling, or grinding components. It has one of the highest hardnesses of PVD coatings and the best thermal resistance. While poor at applications where low friction is key, abrasive and high speed applications are perfect for AlTiN. Its appearance of dark grey to black is used to reduce glare on devices. As such, it is most commonly seen used on surgical instruments.
ZrN (Zirconium Nitride)
text
Coating Type Color Hardness (Hv)
Thickness (µm)
Coefficient of Friction
Max usage Temp (F)
ZrN Pale Gold 1900-2100 1-4 0.4 1050
Zirconium Nitride is called out for medical applications less often than it used to be. Titanium Nitride has replaced it in most applications, as it was another “jack of all trades” type coating for the industry. ZrN was used on both instruments and implant components.
Questions?
Jason Sikora
Engineering Materials Director
937-253-5311 x 273
Jeff Tomczak
Manager – Thin Film Division
937-253-5311 x 206
