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Tercius Justusa, Priscila Gonçalvesa, Martin Seifertb, Sônia M. H. Probsta, Günter Motzb, Aloisio N. Kleina Federal University of Santa Catarina, Mechanical Engineering Department, Materials Laboratory (LabMat), PO Box 476, Br88040-900 Florianópolis, Brazil b University of Bayreuth, Ceramic Materials Engineering (CME), D-95440 Bayreuth, Germany a

EVALUATION OF A POLYMER DERIVED CERAMIC (PDC) ENVIRONMENTAL COMPOSITE BARRIER COATING APPLIED ONTO SINTERHARDENING STEEL

Corrosion processes Metal and alloys in service (thermodynamic instable)

$2.6 trillion of the GDP NACE INTERNATIONAL

Manufacturing processes and Research

Oxides: Thermodynamic stable

Mining, Extractive metallurgy and Metallurgical processing

Oxide ores

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1) Higher surface area 2) Increased free energy

SINTERED FERROUS METAL PARTS Dry corrosion

Wet corrosion

David Young – High temperature oxidation and corrosion of metals

D. R Gabe – corrosion and protection of sintered metal parts 4

BRAGECRIM PROJECT

• University of Bayreuth - CME (Ceramic Material Engineering) DrIng Günter Motz; • Federal University of Santa Catarina– LabMat - Prof. Dr.-Ing Aloisio Nelmo Klein.

Evaluation of a PDC barrier coating onto a sinter-hardening steel. 5

What are PDCs?

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PDCS – POLYMER DERIVED CERAMICS PROCESSING

Ternary Systems SixCyNz Polysilazane Carbo-silicon-nitride 400°C

1400°C

Main by-products: Hydrogen, methane and ammonia gaseous release.

>1400°C

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POLYMER DERIVED CERAMICS Intrinsic chemical and physical-chemical properties of the pure constituting phases:  Exceptional oxidation and corrosion stability;  Crystallization and creep resistance up to high temperatures;

Increasing % of fillers from figures a to c.

Organic – Inorganic transformation Mass loss up to 50% in weight Polymer - 1g/cm3 Ceramic - 2,3 to 2,8g/cm3

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EXPERIMENTAL PROCEDURE pressing

1) Sintered Steel

%wt Chemical Composition (%wt) 97.4% Fe1.5Mo – Astaloy Mo Höganäs 2% Nickel – Epson Atmix 0.6% - Graphite 0.8% of lubricant (acrawax Lonza)

mixing

45 min. Sintering

600MPa

Heating rate – 5°C/min. Debinding – 500°C – 30min. Sintering – 1150°C – 60 min.

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EXPERIMENTAL PROCEDURE 2) PDC Composite Coating Stirring

Stirring

Solvent: Dy-n-Butyl Ether Dispersant: Disperik Zirconium (25 %) (%vol 80) Boron silicate Glass (27.5%) Barium silicate Glass (27.5%) Polysilazane HTT1800 (amorphous SiCN ) Dicumilperoxide (free radical initiator)

Stirring

Spray Coating

Thermal Treatment Heating rate – 3°C/min. Nitrogen Atmosphere Time – 60min

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COATING THERMAL TREATMENT TEMPERATURE Martin Günthner - Journal of the European Ceramic Society 31 (2011) 3003–3010

700°C 750°C 770°C 800°C Glass Tg (°C) Ta (°C) Ts (°C) Boron 440 570 680 Barium 612 770 850

Tg = vitreous transition Ta = softening temp. Ts = sealing temp 11

RESULTS AND DISCUSSION

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SINTER HARDENING STEEL MICROSTRUCTURE After sintering: (1150°C)  Bainite  Retained austenite  Martensite  Pearlite

Density: *7,06 ± 0,03 g/cm3 Average Densification: *89,4 ± 0,4% *geometric method

97.4% Fe1.5Mo +2%Ni+0.6%C 13

SINTERED STEEL TOPOGRAPHIC CHARACTERIZATION Optical Interferometry Sa = 2,03µm Sq = 3,63µm

Ssk = -2,7 Sku = 12,37 Sp = 11,25µm Sv = 23,37µm Sz = 34,60µm

Ssk – Skewness < 1 peaks removed and presence of valleys Sku – Curtosys > 3 High peaks and deep valleys

Coating Thickness = 38μm Sz + standard deviation = 34.6 + 3.63 = 38.22μm Sz = Sp+Sv = maximum height 14

COATING/SINTERED STEEL INTERFACE CROSS SECTION (SEM – SE)

800°C

750°C 15

OXIDATION TEST RESULTS - BARRIER PROPERTIES

 Qualitative method – Prussian Blue; Objective: set coating thermal treatment temperature  Quantitative method – Accelerated oxidation Objective: Kinetics characterization 1) Test t (95% of significance) difference between average results 2) Coeficient of variation

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PRUSSIAN BLUE

700°C

750°C

770°C

800°C

- Sintetic blue pigment - HCl (5 molar) - Potassium ferricyanide K3[Fe(CN)6] 3

𝐹𝑒

+ 𝐹𝑒 𝐶𝑁

↔ 𝐹𝑒

+ 𝐹𝑒(𝐶𝑁)

Coating termal treatment temperature: 770°C and 800°C

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ACCELERATED OXIDATION  Temperature: 450°C  Atmosphere: ambient (dry oxidation) Glass Boron Barium

Tg (°C) 440 612

Group 1 2 3 Total

Ta (°C) 570 770

Ts (°C) 680 850

Sintered 3 3 3 9

Sintered – no coating Coated 770°C – coating thermal treated at 770°C Coated 800°C – coating thermal treated at 800°C

Mass Measurement 1 2 3 4 5 6 7

Coated 770°C 3 6 3 12

Time (hours) 0,5 1 2 5 20 60 100

Coated 800°C 3 6 4 13

For accelerated oxidation characterization the samples were completely coated

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KINECTICS OF OXIDATION  Sintered = 13,1mg/cm2  

Coated 770°C = 9,46mg/cm2 Coated 800°C = 8mg/cm2

(Test T - 95%)

Coated 770°C

Coated 800°C CV < 10%

CV > 15%

 Sintered steel without coating presented a parabolic oxide growing rate :  Fe3O4 – parabolic oxidation  Sintered steel coated and thermal treated at 700 and 800°C presented a behavior similar to the passivating metals at low temperature. 19

CONCLUSION  I was possible to apply a PDC composite containing zirconium and glalss fillers onto a sinter-hardening steel.  Coated samples presented 40% less mass gain when compared with uncoated samples.  Its necessary to modify glass filler composition in order to achieve higher temperatures for coating thermal treatment.

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AKNOWLEGMENT

THANK YOU!

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