Hardness of SS-254SMO (Grade) S31254 (UNS Number) Used in Valve Components

The inquiry is about the hardness of SS-254SMO (Grade) S31254 (UNS Number) used in valve components. The inquiry seeks to clarify whether NACE MR0175 specifies hardness requirements for this material and whether the maximum allowable hardness is 35 HRC as stated in NACE MR0103. In response, the applicable tables for the subject alloy are A.8 thru A.11.

Table A.8

Table A.8 shows that there are no hardness requirements for material in solution-annealed condition used for any equipment or components. However, UNS J93254, the cast version of UNS S31254, in the solution heat-treated and water-quenched condition, has a maximum hardness of 100 HRB.

Table A.9

Table A.9, for downhole tubular components, packers, and other subsurface equipment, indicates that the material must be in the solution-annealed and cold-worked condition with a maximum hardness of 35 HRC. The inquiry’s reference code is MP Inquiry 2017-18 (NACE MR0175 Part3 A.3.2 Table A.8).