Physical Vapor Deposition techniques and influencing process parameters on

coatings

1. Mubarak, A., Hamzah, E., Toff, M.R.M., Hashim, A.H. and Amin, M., (2005), “Review of physical

vapor deposition for hard coatings”,20, pp: 17-18

2. Krishna Valleti , C. Rejin, Shrikant V. Joshi, Factors influencing properties of CrN thin films grown by cylindrical cathodic arc physical vapor deposition on HSS substrates, Materials Science and Engineering A 545,(2012), pp: 155-161

Presented by

D.RATHIRAM NAIK

15MT60R35

IIT KHARAGPUR

M.Tech- 1st year

ContentsIntroduction

Physical Vapor Deposition(PVD)SputteringCathodic Arc PVD

Factors Influencing Sputtering DepositionNitrogen/Argon ratio

Factors Influencing CAPVD coatingsSubstrate roughnessMetal ion etchingPlasma etchingPartial pressure of NitrogenSubstrate temperature and bias voltage

Conclusions

References

IntroductionPhysical Vapor Deposition(PVD):o Sputtering

o Cathodic Arc PVD

Why to prefer PVD:◦ Applications from decorative to high temperature super conducting

◦ Very high deposition rates 25 (μm/sec)

◦ Any type of material we can coat (compounds, metals, alloys, mixtures)

◦ Hard coatings

◦ Resistant to oxidation

DisadvantagesIt generates the less quantity of ionized target atoms than CAPVD

Low ionisation rates

Target poisoning • Deposition rate decreases as Nitrogen partial pressure increases o Nitrogen covering the target

High substrate heating

Influence of factors Steel substrate

Mode:Reactive magnetron sputtering

Reactive gas: Nitrogen

Sputter gas: Argon

N2 / Ar ration = R

As R increasing from 0.1 to 0.7 stress levels in the sample is increases

R on mechanical propertiesNitrogen occupies interstitial positions and buildup the stress TaN is in unstoichiomatric conditiondue to this hardness is going to increases

After reaching stoichiometric after R= 0.5hardness (~40 GPa) is going to decreases

Cathodic Arc PVD Evaporative technique

Used to deposit single and multilayer coatings

Ceramic, metallic, alloys, compounds coatings

High energy input than the PVD sputtering

It generates the highest quantity of ionized targetatoms 50-100%

Highest ionisation rates leads to high deposition rates

Highest adhesion properties

High energy ions removes oxide layers if present

Creation of roughness but it is in atomic levelroughness

Process in CAPVDSOURCE

(Solid / Liquid)

GAS PHASE

SOLID PHASE(Changes in physical morphology)

Evaporation

Transport &

Deposition

CAPVD Unit at ARCI - HYD

REF: [3]

Main components of CAPVDDOOR CATHODES

Al

Cr

Ti

CENTRAL CATHODEAlSi+

PRESSURE GAUGESRotor pumps---- 1X10-3 mbar

Turbo Molecular--1X10-7 mbar

CAROUSEL

Advantages of CAPVDSimple process,

Highly pure thin films obtained

Most popular method for applying hard coatings in tool industry.

Better uniformity

Good surface finish.

Environmentally clean process

High deposition rates

The low voltage power supplies will not damages the target materials.

High vaporization rates are obtained

Disadvantages of CAPVD Formation of macro particle

Excess atoms that are not completely ionized these neutral atoms leads to formation of macro droplet

Material wastage is more in the chamber

Difficult to stabilize Arc

Difficult to evaporate alloys due to different melting points

Only four cathodes are present

Comparison between CAPVD and sputteringFEATURE CAPVD SPUTTERING

Plasma density, m3 1016 - 1020 1014-1018

Ion velocity , m/s (1-2)x104 (3-6)x103 (Ar ions)

Ion energy, eV 50-150 10-40

Macro particle Yes No

Electrical Characteristics High current (Iarc = 30-500A)Low voltage (10-50V)

High voltage (V= ~ 1 KV)Low current (10-2 – 1 A)

Influencing process parameters CAPVD SPUTTERING

Target composition Target composition

Substrate temperature Substrate temperature

Bias voltage Substrate bias voltage

Gas flow rate Ion current density

Ion bombardment rates Ion current density

Choice of base material Choice of base material

Influence of parameters

Substrate roughness of HSS:Inverse relation in between adhesion

strength and surface roughness

Decrease in adhesion strength

So, critical load also decreases

Maximum tensile stress between stylus andcoating

Metal EtchingEtching in CAPVD CrN coatings• Type of metal• Ti (MP = 1933 K) or Cr (MP = 2143 K)

• Time of etching

Reduction in droplet formation with Cr thanTi• Due to difference in Melting Point(M.P)

• Higher the M.P smaller the M.P at cathode

• So lower the micro droplet formation

Etching time

Initially removal oxide layers, dust are removed

Surface damage after 15 minutes

Effect of Ar+N2 Ion etching on surface roughness of cutting tools

Process parameters for Ar+N2 Etching at 100 V, 200 V, 300 V

Parameter Values

Bias voltage 100, 200, 300 V

Chamber temp. 465 0C

Process time 05 min

Argon flow rate 200 sccm

Nitrogen flow rate 20 sccm

High Speed Steel:With respect to bias voltage change in roughness decreases

WC-Co sample:With respect to bias voltage change in roughness increasesDue to grain refinement

Influence of Nitrogen partial pressure (Np)Np (varied over the range (i)5×10−3 – (ii)5×10−2 mbar) on CrN. The grown film exhibiteda dense columnar structure with a defect freesubstrate to coating interface

Stresses development in coatings are less

As Np increases compressive stresses aredecreasing

At (i) Nitrogen occupies interstitial position ofCr and build up stress later at (ii) leads toformation of nitrides

Enhancement in adhesion and crackpropagating resistance(CPR)

Influence of substrate temp. and bias voltage An increase in Tsub 2000 C to 5000 C:

• Formation of droplets

• 50 % fall in corrosion resistance

• 30% increase in adhesion strength

• Increase in defect concentration

Increasing the negative bias Voltage(-50 to -150 V): • Increase in adhesion strength about 30%

• Highly dense close packed orientation in (111)

The columnar grain size (column width) increases with increase in TSub but decreases with increasing VSub

Contd…..! Mechanical Properties:• Decrease in hardness with increase in either TSub or Vsub

• Phase composition and strain energy associated with the films

Correct temperature:• Tsub / Tcoating.melt = 0.3

Conclusions Physical vapor deposition techniques were studied with various influencing parameters

Appropriate recipe gives good mechanical , thermal , corrosion and wear resistance properties

Influencing parameters changes process to process and depending on coatings

Influencing parameters depends on substrate materials

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AcknowledgmentsI would like to thank Mr. N. Ravi (Scientist-E), Dr. Krishna Valle (scientist –D) and Mr. PuneetChandran(research scholar) department of Center for Engineered Coatings, InternationalAdvanced Research Centre for Powder Metallurgy and New Materials (ARCI) – Hyderabad

I would like to thank International Advanced Research Centre for Powder Metallurgy and NewMaterials (ARCI) – Hyderabad

THANK YOU