SURFACE ENGINEERING (1) VAPOR DEPOSITION Prof. Priit Kulu, Eron Adoberg

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).

Deposited coatings CHEMICAL ELECTROCHEMICAL THERMOCHEMICAL ion coating CHEMICAL ELECTROCHEMICAL THERMOCHEMICAL THERMOCOATING VAPOR DEPOSITION MECHANICAL ion transfer (ion alloying) ion mixing/dilution ion composite coating

Comparison of the coating processes

Thin hard coatings Ceramic compounds – metals’ oxides, carbides, nitrides. Coatings with thickness up to 10 μm are considered as thin 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.

Coatings’ processes

Coating process – PVD 1 – cathode; 2 – accelerators; 3 – anode. lower process temperature (250 – 600 ºC) in comparison with CVD process; electrical or magnetic field is applied.

Coating process – CVD Higher process temperature (600 – 1100 ºC) in comparison with PVD process; Chemical reaction is applied.

Coating cycle

PVD-Coating with Dynamic Rotating ARC-Cathodes LARC®: LAteral Rotating ARC-Cathodes rotary table magnetic confinemen system_2 substrates door or backside shield confinement system_1

Structures’ types of the coatings

Microstructure of coatings (1) 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 (2) SEM images of fractured surface of PVD coatings on nitrided steel: a– monolayer TiN, b– monolayer TiCN and c– multilayer TiAlN

Gradient coatings Large Al content The content of coating’s hard component – AlN – gradiently increases through the coating giving the coating’s surface the largest hardness value. TiN adhesion layer Small Al content

Multilayer coatings have bigger toughness. Layer structure hinders cracks’ development. Multilayer coatings are applied, where dynamic loads are present. TiAlN+TiN (allikas: MUK)

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

Nanocomposite coatings (2)

DLC coatings 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; DLC is deposited as the finish layer at the top of the coating. large hardness; chemical inertness; low coefficient of friction

Hard coatings’ properties Color Hardness (GPa) Young’smodulus E (Gpa) Thickness of coating (μm) COF Maximum application temp.°C TiN TiCN TiAlN (mono/ multilayer) AlTiN nACo® (AlTiN/Si3N4) CrN AlCrN TiAlCN+CBC* (CBC – carbon-based top layer) nACo®+CBC* gold copper violet-black black violet-blue silver blue-gray grey 24 32 35/28 38 45 18 20/30 438±80 500±90 301±90 336±13 323±13 1 – 7 1 – 4 1-7 1-4 1,5 – 5 1 – 6 0,55 0,2 0,5/0,6 0,7 0,45 0,3 0,6 0,15 600 400 800/700 900 1200 700 1000 500 450

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

Application of PVD and CVD coatings

Trends in the PVD coatings

Coating application areas

Applications (1) Cutting tools: TiAlN AlTIN TiAlCN nACo® (AlTiN/Si3N4) AlCrN TiAlCN nACo® (AlTiN/Si3N4) nACRo (AlCrN/Si3N4) milling distance Lf [m]

Applications (2) Punches and dies: TiN TiCN TiAlCN + CBC AlCrN

Applications (3) Pressing and casting molds Tribology TiN CrN ZrN AlCrN TiAlCN + CBC Tribology TiAlCN + CBC nACo +CBC nACRo + CBC DLC

Thank you for the attention! Questions?