Dec 3, Comparison of APS, SPS and EB-PVD YSZ coating characteristics for advanced thermal barrier coatings

Transcription

1 Comparison of APS, SPS and EB-PVD YSZ coating characteristics for advanced thermal barrier coatings Brian W. Callen 1, Mitchell Dorfman 2, Jing Liu 2, Alex McLane 2, Riston Roccio- Heller 2,Scott Wilson 3 1.Oerlikon Metco (Canada) Inc. 2. Oerlikon Metco (US) Inc. 3. Oerlikon Metco AG (Switzerland) Thermal Spray of Suspensions & Solutions Symposium Dec 3, 2015.

2 Contents 1 Background of TBC application 2 Scope of work 3 Mterials and Methods 4 Hardness survey of coating structures 5 SPS Parameter study on columnar structures 6 Conclusions and Future Work 7 Acknowledgements Page 2 File Name

3 Background EB-PVD coatings: Have been used for many years on turbine components. Key advantages: strain tolerance and excellent thermal fatigue properties Key disadvantages: high capital cost of equipment, low rate of deposition, high thermal conductivity. APS coatings: Disadvantages of EB-PVD process lead to patented and proprietary APS applied processes back in the early 1990 s, and is now expanding to include SPS. Key advantages: lower capital cost, and faster process time. Key disadvantages: line of sight, sensitivity of process, short spray distance.

4 Scope of Work 8% Yttria Stabilized Zirconia (YSZ) Thermal Barrier Coatings: Hardness depth profile and erosion resistance 1. Porous by Atmospheric Plasma Spray (APS) 2. Segmented by APS. 3. Fine Columnar By Electron Beam-Physical Vapour Deposition (EB-PVD) 4. Columnar by Suspension Plasma Spray (SPS) Parameter study of SPS columnar structures a) Spray distance 2, 3, 4 b) Plasma gas Ar/He vs. Ar/H 2 c) Bond coat roughness APS vs. HVOF Microstructure, hardness, erosion and furnace cycling

5 Materials Suspension Plasma Spray: 8YSZ (Metco 204 composition) 25% wt. loading, particle size < 3 µm. Balance ethanol with dispersant APS: 8 wt%ysz Metco 204NS EB-PVD: 8 wt% YSZ Substrates used: Stainless steel (grit blasted) Hastelloy X with HVOF or APS bond coat Ni 22Co 17Cr 12Al 0.5 Hf 0.5Y 0.4Si (Amdry 386) Hastelloy X with LPPS bond coat Amdry 386 (EB-PVD only)

6 Suspension Plasma Spray Experiment set-up TriplexPro-210 with suspension feed (SinplexPro-180 illustrated). Ar/He and Ar/H 2 gas mixtures Spray distance 2, 3 and 4 inches Prototype 5MPE-SF Suspension Feed unit Suspension feed rate 32 g/min.

7 Test Methods Instrumented Indentation Martens Hardness Vickers indenter HM = F max A s F max maximum applied load (N) As contact area at load (mm 2 ) GE erosion test ( GE specification E50TF121) Alumina grit at 20 degree angle Furnace Cycle Test minutes heat-up minutes steady state at 1135 C minutes cool down

8 Hardness profile 8% Yttria Stabilized Zirconia (YSZ) Thermal Barrier Coatings on stainless steel, no bond coat: 1. Porous by Atmospheric Plasma Spray (APS) 2. Segmented by APS. 3. Fine Columnar By Electron Beam-Physical Vapour Deposition (EB-PVD with bond coat) 4. Columnar by Suspension Plasma Spray (SPS) Testing methods: A. Microstructure by SEM B. Instrumented indentation (Martens Hardness)

9 EB-PVD Benchmark LPPS bond Ni 22Co 17Cr 12Al 0.5Hf 0.5Y 0.4 Si GE-Erosion: sec/mil (IIT-312-6) Page 9

10 8YSZ (M204NS) APS porous GE-Erosion: 3.61 sec/mil (IIT-0025) Page 10

11 8YSZ (M204NS) APS segmented GE-Erosion: 8.49 sec/mil (IIT-0026) Page 11 TBC_SEM-Evaluation_2015_11_18 Stefan Moser

12 8YSZ SPS Columnar GE-Erosion: 5.63 sec/mil (IIT-0027) Page 12

13 Hardness Profiles APS, SPS, EB-PVD 2000 N 2000 N 1000 N 2000 N Method: A.M. Korsunsky et. al. Surface and Coatings Technology 99 (1998)

14 Normalised Erosion Resistance (GE Erosion) Relative Erosion Resistance by coating type APS porous APS segmented SPS columnar EB-PVD Ranking of erosion resistance differs from that of other studies by Curry 1 and by Lima 2 where SPS columnar erosion similar to or better than EB- PVD. Could this be dependent on the particular columnar structures involved? 1. Coatings 2014, 4, Surftec meeting June 19 th 2012

15 SPS Parameter study 8% Yttria Stabilized Zirconia (YSZ) Thermal Barrier Coatings: 1. Fine Columnar By Electron Beam-Physical Vapour Deposition (EB-PVD) 2. Columnar by Suspension Plasma Spray (SPS) Selection of SPS variables: -Bond coat roughness (APS vs. HVOF) -Plasma gas Ar/He vs. Ar/H 2 -Spray distance 2, 3, 4. Testing methods: A. Microstructure by SEM B. Instrumented indentation (Martens Hardness) at 300 N C. Erosion Resistance D. Furnace Cycle Test E. Laser Thermal Gradient Test

16 SPS columnar structure Testing the effect of bond coat, spray gas and spray distance: Spray distance Plasma gas Bond Coat 2 Ar/He Rough (APS) 3 Ar/He Rough (APS) 4 Ar/He Rough (APS) 2 Ar/H 2 Rough (APS) 3 Ar/H 2 Rough (APS) 4 Ar/H 2 Rough (APS) 2 Ar/He Smooth (HVOF) 3 Ar/He Smooth (HVOF) 4 Ar/He Smooth (HVOF) 2 Ar/H 2 Smooth (HVOF) 3 Ar/H 2 Smooth (HVOF) 4 Ar/H 2 Smooth (HVOF) Microstructure Martens Hardness GE erosion resistance Furnace cycle test Laser thermal gradient (select coatings)

17 APS bond coat 2 inches Ar / He gas parameter 3 inches 4 inches Ar / H 2 gas parameter 2 inches 3 inches 4 inches Wider gaps for Ar/H 2 APS bond coat roughness Ra µm

18 HVOF bond coat Ar / He gas parameter 2 inches 3 inches 4 inches Ar / H 2 gas parameter 2 inches 3 inches 4 inches Wider gaps for Ar/H 2 HVOF bond coat roughness Ra µm

19 Martens Hardness 300HM (N/mm2) Hardness change with spray distance inches 3 inches 4 inches 2000 Dense coatings at short spray distance. No other trends Rough BC Ar/He Rough BC Ar/H2 Smooth BC Ar/He Smooth BC Ar/H2 EB-PVD

20 Normalized Erosion Resistance (GE erosion) Erosion change with spray distance Highest hardness coatings. Ar/H 2 hotter- gas mix inches 3 inches 4 inches Rough BC Ar/He Rough BC Ar/H2 Smooth BC Ar/He Smooth BC Ar/H2 EB-PVD

21 Cycles to Failure SPS coatings had similar or better FCT performance than EB- PVD Furnace Cycle Test 250 Test ended at 200 cycles inches 3 inches 4 inches Rough BC Ar/He Rough BC Ar/H2 Smooth BC Ar/He Smooth BC Ar/H2 EB-PVD Low hardness coatings with Rough APS bond coat had best FCT

22 Thermal Gradient Test CO 2 Laser Rig 2.5 cm (1 ) diam Back camera TBC-coated coupon IR camera Laser Back pyrometer (spot size ~6 mm) 5.1 µm wavelength Back cooling air jet Front camera Front pyrometer (spot size ~6 mm) 7.9 µm wavelength 22

23 NRC laser thermal cycling APS bond coat, Ar/H2 2 Thermal conductivity increases with cycling

24 NRC laser thermal cycling APS bond coat, Ar/H2 3 Thermal conductivity constant with cycling Lower density coating is better insulator and more stable

25 Conclusions SPS columnar microstructure has a large impact on performance properties: 1. Effect of rough APS vs. smooth HVOF bond coat: Rough APS coating provided better FCT. No discernable differences in structure 2. Effect of plasma gas: Ar/H 2 had improved erosion resistance compared to Ar/He Slight difference in microstructure 3. Effect of spray distance: Steep drop-off in properties with distance Short distance, dense structure: Good erosion resistance. Poor FCT & Laser thermal gradient stability. Longer distance, lower density: Poor erosion, but improved FCT and Laser thermal gradient stability.

26 Future Work Continued work to characterize and improve SPS YSZ columnar structures to include; Instrumented indentation profiling Conductivity and burner rig testing Adjustments in suspension particle size Bond coat preparation

27 Acknowledgements Oerlikon Metco Colleagues; Hector Cruz Amanda Erhart Petr Fiala Stefan Moser Manfred Stapgens

28 Thank you. Page 28 File Name