When to do post manufacturing hardness test?

[salmon2]

Hi experts, Our products are to NACE MR0175 standard and certification authority will need/witness hardness verification. When should we do the post manufacturing hardness verification? Before or after coating? Say we have a part made of QT 4140 and with QPQ as coating. We have everything including hardness at mid-radius about raw material in MTR, all in compliance.

Hardness testing method I think will be HRC as we are not talking about weld. Hardness limit is max 22 HRC at wet surface per NACE 0175. Any inputs are highly appreciated.

 

[19Delta]

Nace 0175 is a material spec not a coating spec, the hardness should be done before coating. You should be able to be within hardness range with 4140.

 

[blacksmith37]

Or , as the committee routinely answered this question : MR01-75 is a material requirement document, not a Quality Control document.