Electrodeposited Inconel and Stellite like Coatings for Improved Corrosion Resistance in Biocombustors

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1 Electrodeposited Inconel and Stellite like Coatings for Improved Corrosion Resistance in Biocombustors T. D. Hall S. H. Vijapur E. J. Taylor M. E. Inman M. Brady (ORNL)

2 slide 2 Why: Global Initiative Create more efficient, longer lasting, cleaner, and cost effective cookstoves for use in burning biomaterials Nearly 4.3 Million deaths a year are due to smoke inhalation Incomplete combustion producing CO and carcinogens Nearly $40 Billion spent annually on fuel sources Some families spend up to 2 hr a day or 1/3 of income acquiring fuel 1 Billion Tons of CO 2 year from open fires Must improve burning efficiency Must operate at higher temperatures Must design low cost material systems to durably perform in these environments

3 slide 3 DOE Focus Program on Low Cost Coatings Problem: Biomass combustion reactors are subjected to various corrosive attacks due to the wide range of potential materials that will be burned in them, including: Gasoline, grass and other carbon based waste These give off mixtures of: Alkali halides (fly ash particulate) Halogen Acids Water Sulfur and Nitrogen Oxides Potential Solutions: 1. Replace the composition of the internal materials used within biocombustors. Corrosion resistant SS, Ni Alloys, or Co alloys (THESE ARE COST PROHIBITIVE) 2. Apply a high value coating to existing bio-combustors or lower cost steels. Coating could consist of corrosion resistant alloys like Stellite 21 or Inconel 740

4 slide 4 Objective of Program Develop a cost effective, scalable, and flexible electrodeposition based coating process that can be applied to the corrosion sensitive regions of existing and next generation bio-combustors Ni and Co based alloys have been shown to possess excellent alkali/halide attack resistance Co based alloys have been shown to possess sulfidation resistance Mo additions into the metal alloys also seem to improve corrosion resistance and high temperature stability. Cr improves temperature stability and corrosion resistance in high temperature systems Alloy Co Ni Cr Fe Mo W Inconel (base) Inconel (base) Haynes 25 (base) Stellite 21 (base)

5 slide 5 Experimental Plan Outline Substrate: Low cost ferritic or austenitic steels 304 SS, 410 SS, 441 SS 1 x 4 dual sided Coating compositions [Co/Ni] Cr [Mo/Fe] (composition variance) Testing Parameters: CTE (quick CTE test at Faraday within muffle furnace) Coating composition XRF High temperature corrosion test at 700 C in Air 500 hr Salt Spray (Remove after every 100 hr for weight and reapplication) Cross-sectional SEM analysis of oxidation

6 Anode slide 6 Electrolyte Development Used a Hull Cell to Rapidly design electrolyte and processing conditions to deposit binary and ternary alloys consisting of [Ni/Co]-Cr-[Mo/Fe] Used XRF to measure the deposit composition Standard Cr 3+ plating solution g/l CoSO 4 7H 2 O (0.077 M Co 2+ ) 4.8 cm 6.3 cm Cathode Distance from high current edge, cm Elemental composition, % Cr Co cm Standard Cr 3+ plating solution g/l CoSO 4 7H 2 O (0.154 M Co 2+ ) Distance from high current edge, cm Elemental composition, % Cr Co

7 Compositional Screening: Ni-Cr and Ni-Co-Cr w/ Hull Cell slide 7 Hull Cell study shows that a wide range of potential deposit composition can be obtained controlling the Ni concentrations

8 Compositional Screening: Ni-Cr-Fe w/ Hull Cell slide 8

9 Compositional Screening: Ni-Co-Cr-Mo w/ Hull Cell slide 9 Alloy Co Ni Cr Mo Inconel (base) Stellite 21 (base)

10 slide 10 Scale up to 1 x 4 Coupons Using the electrolyte designed within the Hull Cell study and approximate applicable current densities we transitioned to coupon studies Cell 3: 1 x 4 samples prepared simultaneously 29 L cell Volume FARADAYIC Flow Assembly* Samples prepared Pure Ni (Wood s bath) Varying Thickness Pure Cr (1411 and 1318) Varying Thickness NiCr (Varying Ni Conc. / Thickness) NiCrFe (Thickness) NiCoCr and CoCr (Varying Thickness) 1411 *Gebhart, L.E., and Taylor, E.J., U.S. Patent 8,329,006, December 11, 2012.

11 slide 11 As Plated Samples NiCoCr NiCr Ni: 25, Cr: 20, Co:55 NiCrFe CoCr Cr: 15, Co:85 Cr: 20, Co:80

12 slide 12 Corrosion Studies Baseline 100 h salted oxidation [~3 mg/cm 2 - high salt loading and 1 mg/cm 2 low salt loading: sea salt applied to surface from 3.5 w/w% solution prior to corrosion test] Five consecutive 100 h salted oxidation Thermal Cycle Ramping from room temperature to 100 C at 10 C/min Dwelling at 100 C for 30 minutes Ramping from 100 C to 450 C at 1-2 C/min Dwelling at 450 C for 60 min Ramping from 450 C to 700 C at 10 C/min Dwelling at 700 C for 100 hours Ramping from 700 C to room temperature at 10 C/min

13 Comparison Between Substrates after 500 h Salted Oxidation Trials with High Salt Loading [3 mg/cm 2 ] slide 13 Surface Images Post 500 h Cycle SS substrates 100h Salted oxidation 500h Salted oxidation Mass-Loss Post 500 h Cycle 500h Salted oxidation 500h Salted oxidation Ni 60Ni-40Cr 70Ni-20Cr-10Al

14 Comparison Between Substrates and Coated Parts after 500 h Salted Oxidation Trials with High Salt Loading [3 mg/cm 2 ] slide 14 Surface Images Post 500 h Cycle SS441/1411/60Ni-40Cr SS441/1411/25Ni-20Cr-55Co Mass-Loss Post 500 h Cycle Coated 100h 500h Coated 100h 500h SS441/1318/60Ni-40Cr SS410/1318/60Ni-40Cr Coated 100h 400h Coated 100h 400h

15 slide 15 Corrosion Performance Overview Pure Cr and Ni deposit do not maintain adhesion during salted corrosion studies 60/40 ish NiCr and NiCoCr (25/55/20) mixtures seem to have the best corrosion resistance (dependent on thickness) Ternary (Ni/Cr/Fe) deposits did not maintain adhesion during oxidation study (presumably to CTE mismatch) Composition-Electrolyte Base Cr Cr Ni - Wood s plating NiCr NiCr NiFeCr NiFeCr CoCr NiCoCr Salted oxidation (500 h) ~ 50 w/w% NiCr alloys improve corrosion resistance of the base 304SS substrate by at least 70% potentially leading to a 3.4 fold cookstove lifetime improvement

16 slide 16 Baseline Economic Analysis for Exemplar Component Estimate using Cookstove Design from Literature Patent Application# PCT/US2013/ Bulk Wrought Material Pricing 0.61 ft 2 internal area exposed to biocombustor hot zone $/lb Density (lb/in 3 ) Cost per Volume of Material ($/in 3 ) Cost per Area Assume 1/8 Thick Material ($/ft 2 ) Cost of 0.61 ft 2 exemplar component (Fig 41 Right) 718 IN $ $ 6.47 $ $ IN $ $ 5.58 $ $ Haynes 25 $ $ $ $ L SS $ $ 0.77 $ $ SS $ $ 0.46 $ 8.26 $ 5.04 Hastelloy C-22 $ $ 5.95 $ $ Stellite 21 $ $ $ $ Stellite 6 $ $ $ $

17 slide 17 Initial Electrodeposition Based Economic Analysis Base material cost: $5.04 Coating cost is a function of the number of units produced Coating Cost Estimate Patent Application# PCT/US2013/ Line No. Plant Parameters 10,000 Units 100,000 Units 1,000,000 Units 1 Cylinder Size 0.61 ft ft ft2 2 Run Time (sec) Total Units/Hr Total Hours worked per day Units/Day (24 hr.) Days worked per year Units/Yr. (348 days) 16, ,632 1,069,056 8 Plating Line Cost ($/unit) $0.48 $0.06 $ Material Cost ($/unit) $2.03 $1.29 $ Labor Cost ($/unit) $12.52 $1.56 $ Total Cost ($/unit) $15.03 $2.91 $1.69

18 slide 18 Overall Conclusions Demonstrated a wide range of [Co/Ni] Cr [Mo/Fe] alloy coating compositions can produced Demonstrated process scalability from a Hull Cell to flat coupons Demonstrated the potential of specific coatings to surpass 500 h accelerate high temperature corrosion testing 50 w/w% NiCr alloys improve corrosion resistance of the base 304SS substrate by at least 70% potentially leading to a 3.4 fold cookstove lifetime improvement Demonstrated that the process maybe an economically viable approach for improve cook stove biocombustor lifetimes Cost estimate for 50 w/w% NiCr coating is $2.93/ in 3 or $1.69 per 4 mil coating on a 0.61 ft 2 component produced at 1,000,000 units per year This would realize a 89% cost reduction compared to base IN625 materials

19 slide 19 Next Steps Evaluate the potential of other alloy systems Co-Ni-Cr Ni-Cr-Mo/W Addition of Si or Al to the deposit Validate performance in combustion test rigs at ORNL

20 slide 20 Special thanks to all our team members for their support THANK YOU FOR YOUR ATTENTION! QUESTIONS? Contact Information: Tim Hall, Maria Inman, or EJ Taylor Ph: DE-SC