Prof. Petri M.J. Vuoristo

Tampere University of TechnologyDepartment of Materials Science, Tampere, Finland

Functional and Protective Coatings byNovel High-Kinetic Spray Processes

Ville MatikainenJoonas RantanenHeli KoivuluotoAndrea Milanti

Davide FantozziMikko Kylmälahti

Acknowledgements

Principle of the thermal spray coating process

11.11.2014 3

Classification of thermal spray coating processes accordingto the type of energy source used in the process.

11.11.2014 4

Overview of particle temperatures and velocities fordifferent spray processes; process names from TopGunto K2 refer to various HVOF systems. Source: H.C. Starck GmbH

11.11.2014 5

Comparison of characteristics of coatingsdeposited by different thermal spray processes

11.11.2014 6

Influence of oxygen/fuel ratio l on flame temperaturel = 1 for stoichiometric combustion

11.11.2014 7

Reproduced from Kreye, H.; Gärtner, F.;Kirsten, A.; Schwetzke, R. High-velocityOxy-fuel Flame Spraying State of theArt, Prospects and Alternatives. In 5.Colloquium on High Velocity FlameSpraying; GTS e.V.: Erding, Nov. 16 –17, 2000.

Brief history of HVAF spraying

• The process was invented in 1982 by James A. Browning– A cheaper alternative to HVOF (air vs oxygen)– The first commercial systems were available by the late 1980’s.– Used kerosene and air for combustion (oxygen and hydrogen for start up)

• Introduction of Active Combustion technology by UniquecoatTechnologies in 1999.

• Commercial spray equipment based on the AC technology:– UniqueCoat Technologies: M2 Active Combustion HVAF (AC-HVAF) spray gun– Kermetico: AcuKote AK-HVAF guns (AK-05, AK-06, AK-07)– UniqueCoat Technologies: M3 Supersonic Air Fuel spray gun

8www.kermetico.comwww.uniquecoat.com

Particle velocity and temperature

11.11.2014 9Source: UniqueCoat Technologies, LLC

0

500

1000

1500

2000

2500

0 200 400 600 800 1000

Particle Velocity, m/sec

Par

ticle

Tem

pera

ture

,oC

Plasma

Melting Temperature of Metals

Arc

HVOF-1

HVOF-2

QuasarAC-HVAF(2st gen)M2 Gun

Cold SprayProcesses

Detonation

Hot Mode

Cold Mode

UltraCoatSAF(3d gen)M3 Gun

100 kW200 kW

350 kW

HVAF Process Principle

11/11/2014 10

2nd generation HVAF• Kermetico AK-07• Uniquecoat M2

3rd generation HVAF• Uniquecoat M3

Fuel(1) inPowder in

Air in

Fuel(2) inAir in

Catalytic ceramic,Activating combustionStartup

Sparkplug

Modified from patent (US2011229649A1)

www.kermetico.com

HVAF spray system at TUT/DMS

11.11.2014 11

HVAF spray system atTUT/DMS

11.11.2014 12

HVAF Process Characteristics

• Lower propane flame temperature with air(HVAF) compared to pure oxygen (HVOF)– Oxygen: ~2820 ºC– Air: ~1970 ºC

• Higher particle velocity• Less oxidation• Lower porosity• High bond strength• Hard, wear resistant coatings

• Suggested particle size distributions– Carbides -30+10 (or smaller -25+10, +-25+5)– Metals -45+15 (or preferrably -40+20, or narrower)

11.11.2014 13

10 µm

10 µm

HVO

FH

VAF

• Very dense and hard WC-Co-Cr coatings can be sprayed with M3Supersonic Air Fuel gun

• Hardness 1595 HV0.3• Fine and dense structure• Low process temperature prevents the dissolution of fine carbides (<1 µm)

11.11.2014 14

WC-10Co-4Cr

Influence of particle type and size on propertiesof HVAF sprayed two Cr3C2-based coatingsPowders used in experiments

11.11.2014 15

Particle size ranges for powders

11.11.2014 16

Structure of Cr3C2-25NiCr (Amperit 588.025) samplecoated with 300 mm spray distance and 160 g/min feed

11.11.2014 17

Structure of Cr3C2-25NiCr (Amperit 588.074) samplecoated with 300 mm spray distance and 170 g/min feed

11.11.2014 18

Structure of Cr3C2-37WC-18M (WOKA 7504) samplecoated with 300 mm spray distance and 210 g/min feed

11.11.2014 19

Structure of Cr3C2-37WC-18M (WOKA 7502) samplecoated with 300 mm spray distance and 250 g/min feed

11.11.2014 20

Roughness values for different spray conditionsof Cr3C2-25NiCr (Amperit 588.025) samples

11.11.2014 21

Roughness values for different spray conditionsof Cr3C2-37WC-18M (Woka 7504) samples

11.11.2014 22

Hardness of Cr3C2-25NiCr (Amperit 588.025 / 588.074)and Cr3C2 -37WC-18M (Woka 7504 / 7502) HVAF coatingswith constant parameters.

11.11.2014 23

Summary and conclusions• The novel HVAF process enables deposition of dense,

hard and wear resistant hardmetal coatings with excellenttechnical properties

• The main benefits in HVAF are:– Lower flame temperature vs. HVOF– Higher retention of carbides producing exellent coating properties– High powder feed rates for high production rates

• Powder properties are important in the HVAF process,though both fine HVAF size and coarser HVOF sizepowders can be sprayed by the novel 3rd generationHVAF technology.

11.11.2014 24