Coatings for implants and instruments continue to evolve as manufacturers seek the best surface for their devices. Attendees will leave this session with knowledge of new coating research and manufacturing techniques. Three suppliers will speak on the benefits, applications and manufacturing processes of three different coatings. A Q&A with all three presenters will follow.
5. Cells found in Bone
https://www.boundless.com/biology/the-musculoskeletal-system/bone/cell-types-in-bones/
6. 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
7. 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
8. 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
9. 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)
10. 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
13. 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
15. 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
16. 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
17. 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
19. 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
20. Chemical Properties
Some of the important variables contributing to the
Chemical composition of the coating include:
• Starting powder
• Phase composition of the coating
21. 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?
22. 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
23. 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
25. 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.
26. 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
27. 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
28. 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
29. 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
30. 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
32. confidential
Medthin™
2
Medthin™ biocompatible coatings
Ion release reduction
DLC and AlTiN for Color Coding and
Anti-Reflection
Wear protection
Hard coatings
ISO 13485, 10 coating centers globally
Development of new technologies and
coatings such as HIPIMS SiN in
LifeLongJoints LLJ
33. 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
34. 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
35. 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
36. confidential
MedthinTM 65 Ti- Process Impact on PEEK
PEEK crystallinity was checked before and after MedthinTM 65 Ti
Differential Scanning Calorimetry DSC
Fourrier Transform Infrared Spectroscopy, FTIR
Gel permeation chromatography GPC
6
37. confidential
MedthinTM 65 Ti on PEEK – DSC analysis
In black no coating (reference)
In red pre blasted and coated
In blue only coated
7
38. confidential
MedthinTM 65 Ti on PEEK – FTIR analysis
Blasted and coated with
Medthin 65 Ti
8
Coated with Medthin 65 Ti
39. 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
40. confidential
Scanning Electron Micrographs
Showing the coating roughness and morphology
Some heterogeneity (porosity) was noticed at high magnification
10
MedthinTM 65 Ti on PEEK – Morphology
10µm
MedthinTM 65 with 5 µm thickness
41. 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
42. 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
43. 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°C
High Energy low deposition
rate
44. confidential
MedthinTM 65 Ti – Coating Features
ASTM F 1147-05 - Tension testing
of calcium phosphate and metallic
coatings
14
Coating MedthinTM 65 Ti
Chemistry
From Ti targets gases used for coating
Titanium Grade II
ASTM F67
Thickness Up to 20 microns
Structure*
SEM observations
Slightly Porous
Roughness*
ISO 4287 and 4288:1996
Ra about 1 micron
Adhesion to substrate*
ASTM F 1147-05
>20MPa
* Nominal coating thickness
5µm
46. 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
47. 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
48. 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
49. 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
50. 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
51. confidential
Contacts
21
Michael Helmes
Sales Manager, North America
michael.helmes@ionbond.com
IHI Ionbond, Inc.
1823 E. Whitcomb Ave
Madison Heights, MI
USA
Phone +1 248 398 9100 Ext. 2227
Cell Phone: + 1 949-375-6822
Or
Dr. Antonio Santana
antonio.santana@ionbond.com
Global Head Segment Medical
http://www.ionbond.com/en/coating-services/medical/
53. 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.
54. 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
55. 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
56. 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)
59. 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
60. 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
61. 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.
62. 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.
63. 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.
64. 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.
65. 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.
66. 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.
67. Questions?
Jason Sikora
Engineering Materials Director
jsikora@techmetals.com
937-253-5311 x 273
Jeff Tomczak
Manager – Thin Film Division
jtomczak@techmetals.com
937-253-5311 x 206
