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SURFACE ENGINEERING (1)

VAPOR DEPOSITION

Prof. Priit Kulu, Eron Adoberg

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Surface properties of material/part

Wear− mechanical;− corrosive-mechanical.Criteria: wear resistance (by mass/volume, relative)

Methods of surface reinforcement− peening;− surface alloying and hardening;− coatings (sprayed coatings, vapor deposited coatings, cladded

coatings, galvanic coatings, diffusion coatings);− metal cladding (bimetal materials).

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Deposited coatings

• CHEMICAL

• ELECTROCHEMICAL

• THERMOCHEMICAL

• THERMOCOATING

• VAPOR DEPOSITION

• MECHANICAL

ion coating

ion transfer

(ion alloying)

ion mixing/dilution

ion composite

coating

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Comparison of the coating processes

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Thin hard coatings

Advantages:• abrasive, adhesive, etc. wear decreases;• pad growth avoided;• tribological properties improve, thus improving its service life;• need for lubrications decreases.

Coating does not affect the geometry and size of the coated detail.

Ceramic compounds – metals’ oxides, carbides, nitrides.

Coatings with thickness up to 10 μm are considered as thin coatings.

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Coatings’ processes

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Coating process – PVD1 – cathode;2 – accelerators;3 – anode.

• lower process temperature (250 – 600 ºC) in comparison with CVD process;

• electrical or magnetic field is applied.

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Coating process – CVD

• Higher process temperature (600 –

1100 ºC) in comparison with PVD process;

• Chemical reaction is applied.

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Coating cycle

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PVD-Coating with Dynamic Rotating ARC-Cathodes

LARC®: LAteral Rotating ARC-Cathodes

rotary table

magneticconfinemensystem_2

substrates

door or backside shield

magneticconfinement

system_1

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Structures’ types of the coatings

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SEM image of fractured surface of PVD coating on hardmetal. a- TiN coating: 1 – HM substrate; 2 – Ti adhesion layer; 3 – TiN coating; 4 – coating surface with microdroplets.

b- multilayer TiAlN: 1– HM; 2 – Ti adhesion layer; 3 – TiN layer; 4 – TiAlN layer; 5 – TiAlN/AlN multilayer coating; 6 – TiAlN coating; 7 – coating surface with microdroplets

Microstructure of coatings (1)

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Microstructure of coatings (2)

SEM images of fractured surface of PVD coatings on nitrided steel: a– monolayer TiN, b– monolayer TiCN and c– multilayer TiAlN

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Gradient coatings

Large Al content

TiN adhesion layer Small Al content

The content of coating’s hard component – AlN – gradiently increases through the coating giving the coating’s surface the largest hardness value.

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Multilayer coatings

TiAlN+TiN (allikas: MUK)

Layer structure hinders cracks’ development.

Multilayer coatings are applied, where dynamic loads are present.

Multilayer coatings have bigger toughness.

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Nanocomposite coatings (1)2 phases appear during the deposition process: nanocrystalline AlTiN (hard) and amorphous Si3N4 (tough) Advantages:

• very high nanohardness and toughness

• very high temperature resistance

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Nanocomposite coatings (2)

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DLC coatings

DLC is deposited as the finish layer at the top of the coating.

• large hardness;

• chemical inertness;

• low coefficient of friction

DLC (diamond-like carbon) coatings: mechanical, chemical, optical and electric properties are similar to that of natural diamond, but does not have an even crystalline structure;

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Hard coatings’ properties

Coating ColorHardness

(GPa)

Young’smodulusE (Gpa)

Thickness of coating

(μm)COF

Maximum application

temp.°C

TiNTiCNTiAlN (mono/multilayer)AlTiNnACo® (AlTiN/Si3N4)CrNAlCrNTiAlCN+CBC*(CBC – carbon-based top layer)nACo®+CBC*

goldcopperviolet-black

blackviolet-blue

silverblue-graygrey

grey

2432

35/28

3845

1832

20/30

20/30

438±80500±90301±90

336±13323±13

1 – 71 – 41 – 4

1 – 41 – 4

1-71-4

1,5 – 5

1 – 6

0,550,2

0,5/0,6

0,70,45

0,30,6

0,15

0,15

600400

800/700

9001200

7001000

500

450

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Diagram of sliding wear testing results by RT. Drum (C45 steel) wear track width and versus coatings E/H ratio.

190

8590

100

180

2 2,62,32,130

15

30

45

60

75

90

105

120

135

150

165

180

195

210

E/H: TiCN 18,8 TiN 15,4 TiAlN 15,2 AlTiN 14,4 NaCo 11,1

C45 s

teel

dru

m s

lid

ing

wear

test

wear

track w

idth

an

d d

ep

th (

μm

)

wear track width

wear track depth

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Application of PVD and CVD coatings

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Trends in the PVD coatings

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Coating application areas

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Applications (1)Cutting tools:• TiAlN• AlTIN• AlCrN•TiAlCN• nACo® (AlTiN/Si3N4)• nACRo (AlCrN/Si3N4)

milling distance Lf [m]

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Applications (2)

Punches and dies:• TiN• TiCN• TiAlCN + CBC• AlCrN

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Applications (3)Pressing and casting molds• TiN• CrN• ZrN• AlCrN• TiAlCN + CBC

Tribology• TiAlCN + CBC• nACo +CBC• nACRo + CBC• DLC

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Thank you for the attention!

Questions?