Kao Zoua Yang (Ph.D. Student), Benjamin Church (Advisor) Characterization of Aluminum Oxide in Austenitic Steels in Petrochemical Industries Kao Zoua Yang (Ph.D. Student), Benjamin Church (Advisor)

Introduction Two types of oxides in petrochemical industry. Chromium oxide and Aluminum Oxide. Aluminum oxide is resistant to steam and chemically stable at high temperatures[1,2,3]. Aluminum Oxide Layer Steel Substrate C2H4 Coked Layer Figure 1. Application of aluminum oxide in petrochemical industry.

Methodology In this experiment, there were two alumina formers (AFA 1 and AFA 2) and one chromia (CFA) former were selected. Table 1. Nominal Compositions of Samples AFA 1 AFA 2 CFA 4.7 wt. % Al 3.8 wt.% Al 0 wt. % Al 25.1 wt.% Cr 23.1 wt.% Cr 39.7 wt.% Cr 32.7 wt.% Fe 33.5 wt.% Fe 38.0 wt.% Fe 35.0 wt.% Ni 37.0 wt.% Ni 30.8 wt.% Ni

Figure 2. Average Mass Measurements of Oxidized Samples. Test Parameters Samples were oxidized in a cycle mimicking petrochemical cleanout process at 850°C for 12 hours and 915°C for 1 hour in flowing de-aerated steam. The ramp rate of the temperatures was 10°C/min. Figure 2. Average Mass Measurements of Oxidized Samples.

Results x10,000 15keV O Cr Fe Ni O Al Cr Fe Ni O Al Cr Fe Ni x10,000 Figure 3. CFA SEM Line Scan Figure 4. AFA 1 SEM Line Scan Figure 5. AFA 2 SEM Line Scan

Conclusion CFA, AFA 1and AFA 2 samples were oxidized in steam and then characterized in SEM. Line scans were performed and the oxide layer was observed. Line scans indicated that AFA 1 and AFA 2 formed aluminum oxide scales while the CFA formed chromium oxide. AFA materials will have better durability and resistance to high temperature corrosion as experienced in petrochemical processes. Further studies will involve XRD characterization and kinetics studies of oxide growth.

Acknowledgments MetalTek International Duraloy Technologies Lizeth Nayibe Ortiz Reyes Advanced Analysis Facility at UWM Research sponsored by ARPA-E; DE-AR0000690

References Muralidharan, G., et al. “Development of Cast Alumina- Forming Austenitic Stainless Steels.”Jom, vol. 68, no. 11, 2016, pp. 2803–2810., doi:10.1007/s11837-016-2094-8. Church, B, et al. “An initial evaluation of the effect of alloy composition and oxide layer on high temperature coking resistance of heat resistant alloys.” NACE International, 2016, NACE-2016-7886. Church, B et al. “High Temperature Coking Resistance of an Alumina Forming Alloy.” NACE International, 2016, NACE- 2017-9784.