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60 MARCH 2017 MATERIALS PERFORMANCE NACE INTERNATIONAL: VOL. 56, NO. 3 FIGURE 2 Microstructure of the weld zone for Sample 1 showing Cr 3 C 2 precipitation. FIGURE 3 Microstructure of Sample 2 with point analysis for the weld zone showing TiC precipitation. In the ERNiCrMo-3 (Sample 2) weld re- gion, Ti, Nb, and Mo elements in the weld combined with extra carbon, which resulted in the precipitation of nonchromium car- bides (Figure 3) in grain boundaries that prevented depletion of chromium in the ma- trix and increased corrosion resistance and sensitization in comparison to Sample 1. 8 The ERNiCu-7 weld material has higher manganese content (4 wt%). This element is considered to be detrimental to pitting resistance in a sulfur solution environment because of the formation of manganese sul- fide (MnS) 9 inclusions, which create active anodic sites at the SS surface. The presence of compositions such as MnS at the grain boundary reduce resistance to local corro- sion and decrease overall resistance to corrosion. 10 Conclusions • The ERNiCrMo-3 weld material is superior to ERNiCu-7 and ER316L SS weld materials for SCC resistance. • Ti, Nb, and Mo elements in the ERNi- CrMo-3 weld mat erial p er form ed ef fe ctively in c omp ari s on to th e ERNiCu-7 weld material. • MnS and nonmetallic compositions reduced the corrosion resistance of the ERNiCu-7 weld material. References 1 ANSI/NACE MR0175/ISO 15156, "Petroleum and natural gas industries—Materials for use in H 2 S containing environments in oil and gas production" (Houston, TX: NACE Inter- national, 2015). 2 P.R. Roberge, R. Winston Revie, Corrosion In- spection and Monitoring (Hoboken, NJ: Wiley Publication, 2007), pp. 69-70. 3 N. Rokuro, "Characterization and Perspec- tive of Stress Corrosion Cracking of SS (Type 304 and 316) in Acid Solution Using Constant Load Method," Corros. Sci. 49, 1 (2007): pp. 81-91. 4 V. Cihal, Intergranular Corrosion of Steels and Alloys (Amsterdam, The Netherlands: Else- vier Science, Ltd., 1984). 5 A.A. Pardo, et al., "Inf luence of Ti, C, and N Concentration on the Intergranular Corro- sion Behavior of AISI 316 and 321 Stainless Steels," Acta Materialia 55 (2007): pp. 2,239- 2,251. MATERIALS SELECTION & DESIGN