[MW:18754] Query on NACE MR-0175 | Hardness restriction on Weld overlay

Dear Experts,

I have a query on MR-0175/ISO 15156 and the and the applicability of <22 HRC restriction on 13% Chromium components and overlay.

The following info is regarding a Valve:

·         Other wetted components (such as stem, Bonnet bush) made of forging and bar are double tempered to bring the hardness under 22 HRC.

·         The obturator material is ASTM A 216 Gr. WCB and the Overlay is 13% Chromium (1.6 mm thickness).

·         However, for the 13% Chromium overlay to be brought under 22 HRC, double tempering would take the base material WCB to >720°C, at which the base material properties would be affected at the cost of bringing the overlay hardness under 22 HRC

How is the Hardness issue of 13% chromium overlays addressed in the industry?

Thank you for taking time to reply.

Regards

Ram

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