Presentation on nanocomposite hard coating submitted for the evaluation of Course "Seminar and Technical Writing CR798"

1. Nanocomposite hard coating
Seminar And Technical Writing (CR798)
(Autumm 2021)
Course Instructor- Prof. Debasish Sarkar
Presented by :
Abinash Kumar
(519CR6010)
Department of Ceramic Engineering,
National Institute of Technology, Rourkela, Odisha

2. OUTLINE OF PRESENTATION
 Introduction
 Nanocomposite coating
 Classification of hard coating
 Hardness of a material with respect to grain size
 Material selection for nanocomposite hard coating
 Synthesis techniques
 CVD
 PVD
 Characterizing techniques
 Nanoindentation
 Micro-scratch tester
 Application of hard coating

3. INTRODUCTION
 The protection of materials by hard coatings from
physical and chemical degradation is one of the most
important and versatile means of improving component
performance.
 Nanocomposite hard coating enhances the mechanical
and functional property of material.
►Wear, corrosion, abrasion, and fatigue resistance
►Enhances the tool life of various cutting tool and
reduces energy consumption.
TiN, WN, CrN, TiC etc. are some of the hard single phase
coatings. Ternary, quaternary nanocomposite systems are
developed to achieve high hardness, toughness and low
coefficient of friction for many industrial application from
a single coating. E.g.: AlSiN, AlTiSiN etc.

4. NANOCOMPOSITE COATING
 Nanocomposite is a multiphase solid material where one of the
phase has a dimension less than 100 nm.
 Nanocomposite hard coatings are composed of new class of
materials consisting of at least two separate phases of a
nanocrystalline and/or amorphous phase or combination of both,
exhibiting unique physical, chemical and mechanical properties.
 Nanocomposite coatings are usually formed from ternary or
quaternary system with nanocrystalline (nc-) grains of hard
transition metal-nitrides(TiN,TiAlN etc), carbides(TiC etc),
borides(TiB2,TiB etc), oxides(TiO2,Al2O3 etc) or
silicides(TiSi2,ZrSi2 etc) surrounded by amorphous
matrices(BN,C etc).
 TiAlSiN coatings exhibited nanostructured composite
microstructure consisting of solid-solution (Ti,Al,Si)N
crystallites and amorphous Si3N4

5. Contd.
 Nanocomposite films shows different nanostructures which are categorized into three
groups such as
i. columnar nanostructures consisting of grains assembled in nanocolumns,
ii. a dense globular nanostructure with nanograins surrounded by a tissue phase and
iii. nanostructures composed of mixture of nanograins of different crystallographic
orientation

6. Classification
 hard coating material can be divided in 3 categories on the basis of their chemical
bonding
 Nanocomposite hard coating on basis of its hardness can be classified as
Metallic hard materials TiB2, TiC, TiN, ZrN, CrN, WC, VN
Covalent hard materials BN, C(diamond) B4C, AlN, SiC,
Ionic hard materials Al2O3, TiO2, ZrO2, HfO2, MgO
Hard material H> 20GPa TiAlN, TiAlSiN
Super hard materials H> 40GPa
Ultra hard materials H> 60GPa

7. Hardness of a material with respect to grain size
 A resistance to plastic deformation is defined as hardness of a material. High hardness in the
nanocomposite is due to (a) dislocation induced plastic deformation, (b) nanostructure of material and
(c) cohesive forces between atoms.
 According to Hall-Petch relationship:
 Hardness and strength of the materials
depends on the dislocation movement, when
high energetic ions bombard on the surface of
the growing film leading to decrease in
crystallite size with enhancement of film
hardness.
 On further decrease of crystallite size resulting
in softening with decrease in hardness and
strength of the material due to grain boundary
sliding.

8. Material selection for nanocomposite hard coating
 The hard nanocomposite coating is characterized by its hardness H as well as by its
Young’s modulus E and elastic recovery We.
 It should exhibit four necessary conditions:
ratio of H/E = 0.1
high elastic recovery We > 60%
the compressive macro stress (σ< 0)
dense void free microstructure
 H/E (plasticity index) and H3/E2 ratio is important parameter for tribological application.
Both ratio increases when nanocrystals or multilayer structure was formed. Higher the
ratio better is the abrasive resistance
 The ability to withstand at higher temperature presence of metastable state is necessary.
 It should have good adhesion to the substrate and also good cohesion between different
phases.

9. Atmospheric Pressure CVD (APCVD)
Low pressure CVD (LPCVD)
Plasma enhanced (PECVD)
Synthesis techniques
Physical vapor deposition (PVD) Chemical vapor deposition (CVD)
Magnetron sputtering
Ion Beam Deposition
Ion Beam Deposition
Atomic layer deposition

10. Chemical vapor deposition
 vacuum deposition method which refers to activation of gaseous reactant,
followed by the chemical reaction of reactant, causing deposition of solid or
coating on the substrate material.
 uses thermally induces chemical reactions with reagent supplied in form of gases.
 chemical reaction takes place by 2 types:
 Heterogeneous- Reaction which causes coating or deposition taking place
near or on the heated substrate surface, and
 Homogeneous- Reaction which gives powder and takes place in gas phase
Advantages:
 very high deposition rate
 Films are consistent and does not require high
vacuum
 Materials deposited are free from contaminants.
 Manageable density and grain size of deposits
 Deposition can occur even at holes, hollow or closed
areas, interior surface, threads, etc.
 High bonding with the substrate material
Disadvantages:
 Requires very high temperature
 Leads to stress in the deposited film
 Limited film thickness due to coating stress
 Complex and expensive process
 Reactants have corrosive, toxic or moisture sensitive
characteristics
 Due to various properties of reactant, there is low Yield
of the reaction

11. Working of CVD
 The basic steps of CVD involve:
1. transfer of reactant by the forced convection
to the chamber
2. activation of gaseous reactants
3. chemical reaction of reactant forming a stable
deposit
4. adsorption of gaseous reactants on surface of
the substrate
5. dissolution and surface diffusion on the
surface
6. Finally, desorption of unreacted species and
by-products and forced out as exhausts

12. Physical vapor deposition
 process of vaporization of solids, followed by surface coating
 vacuum coating process, which occurs at low pressure ranging 10-3 – 10-9
Torr
 thin coating bonded to surface is deposited atom-by-atom and gives
durable improved appearance coatings
 reduces friction, gives adhesion, hardness, lubricity, and damage
resistance
Advantages:
 Substrates have low temperature
 Complex thin coatings can be obtained
 Coating can be done on any type of inorganic material
 By-products obtained are less in quantity
 Environment friendly method
Disadvantages:
 Expensive and requires complex machines and
skilled operators
 Slower coating rate
 Does not coat under cuts, holes, hollow spaces, etc.
 Difficult to obtain doping

13. Working of PVD
 This method involves four steps under vacuum
conditions:
→ Evaporation: Bombardment of material by
energy source and the atoms vaporize from
the surface of the target
→ Transportation: Transferring of vaporized
atom to the material to be coated from the
target
→ Reaction: Reaction of gases with the metal
atoms during transportation
→ Deposition: Formation of the coating by
deposition of the coating material, which
forms strong bond with the substrate, and
gives lasting adhesion as some atoms
penetrates to the surface.

14. Magnetron sputtering
 process of thin functional coating by charging the
sputtering cathode electrically followed by plasma
formation leading to ejection of material from
target surface.
 Cathode material is eroded and sputtered atoms are
deposited on substrate to form coating of original
cathode.
 Argon ions with high energy hit the target and
atoms are released from the target depositing on the
substrate forming a thin coating
Advantages:
 Uniform and good density of film or coating on
substrate
 Good quality film or coating with low impurity
 Scalability is high
 Low scattering and absorption
 Deposition rate is high for metals
Limitations:
 Low rate of deposition for dielectrics
 Directionality is low
 Expensive and complex
 Leads to heating of substrate

15. Characterization techniques
PROPERTIES STANDARD METHODS
Chemical composition on atomic scale wavelength-dispersive X-ray (WDX); Energy-dispersive X-
ray (EDX).
Phases present in coating X-ray nanodiffraction; transmission electron microscopy
(TEM)
Surface topography; film thickness Surface profilometer, Scanning electron microscopy (SEM)
Microstructure on nanometer scale Field emission scanning electron microscopy (FESEM),
TEM
Mechanical property like hardness,
fracture toughness, elasticity stress strain
analysis
Nanoindentation
Adhesion of coating with substrate,
coefficient of friction
Micro scratch tester, nanoindentation
Evaluation of mechanical properties and adhesion of coating onto substrate is of great industrial
importance

16. NANOINDENTATION
 A prescribed load is applied to an indenter in contact with a specimen.
As the load is applied, the depth of penetration is measured.
 The area of contact at full load is determined by the depth of the
impression and the known angle or radius of the indenter.
 The hardness is found by dividing the load by the area of contact.
𝑯 =
𝑷𝒎𝒂𝒙
𝑨𝒄
 Shape of the unloading curve provides a measure of elastic modulus.
substrate
coating
indenter
Initial step Loading cycle Holding
(elastic recovery of material)
Unloading
(pure elastic recovery)
Final step

17. Schematic of Nanoindentation
Force Transducer
Microscope
Indenter
Sample
Optical fiber Intender heat and displacement sensor

18. INDENTER GEOMETRY
Indenter
type
Projected area Semi angle
(θ)
Effective
cone angle
(α)
Intercept
factor
Geometry
correction
factor (β)
Sphere A= π2Rhp N/A N/A 0.75 1
Berkovich A= 3hp
2tan2θ 65.30 70.2996o 0.75 1.034
Vickers A= 4hp
2tan2θ 680 70.320 0.75 1.012
Knoop A= 2hp
2tanθ1tanθ2 θ1= 86.250
θ2= 650
77.640 0.75 1.012
Cube corner A= 3hp
2tan2θ 35.260 42.280 0.75 1.034
cone A= πhp
2tan2α α α 0.72 1

19. Mechanical property measured using nanoindentation
 Hardness Ac= 24.5hc
2 𝑯 =
𝑷𝒎𝒂𝒙
𝑨𝒄
 Young’s modulus
𝟏
𝑬𝒓
=
𝟏−𝝂𝟐
𝑬
+
𝟏−𝝂𝒊𝟐
𝑬𝒊
 Contact stiffness 𝐒 = 𝟐𝛃 𝐄𝐫 (𝐀/𝐫)𝟐
 Stress-strain analysis
 Time-dependent creep measurement
 Fracture toughness Kc = 𝜶
𝑬𝟎.𝟓
𝑯𝟎.𝟓
𝑷
𝑪𝟏.𝟓
 Elastic and plastic work/ energy of deformed material area under the curve (integration)
 Nano-scratching of thin films or coating Wv =
𝟏
𝟐
𝐜𝐨𝐬(𝟕𝟎. 𝟑)dn
2l

20. Micro-scratch testing
 Adhesion is the interfacial forces between two surfaces, which held them together.
 Adhesion of coating is big concern for industrial application.
 Micro-scratch tester is used to evaluate the coating adhesion strength, friction coefficient of
coating, interfacial toughness
Working principle:
 Scratch tester determines the tractional force experienced by the indenter from the substrate due to
an increasing normal load.
 Piezoelectric transducer converts this mechanical stress to an electrical signal.
 The ratio between the traction and normal force gives the coefficient of friction value.
 The load at which the coating fails is known as critical load (Lc).
 Crtical load is related to work of adhesion as:
𝑳𝒄 =
𝝅𝒅𝟐
𝟖
𝟐𝑬𝑾
𝒕
𝟏
𝟐
 The critical load can be estimated from the scratch test experiment by determining the point of
change of slope in the coefficient of friction vs. normal load curve

21. Schematic of micro-scratch tester

22. APPLICATIONS

23. REFERENCES
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materials processing technology 209.1 (2009): 165-170.
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(1986): 2661-2669
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Vacuum Science & Technology A: Vacuum, Surfaces, and Films 14.1 (1996): 46-51.
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