NACE MR0175 Article 5.2 Overlays

5.2 overlaysoverlays applied to carbon and low-alloy steel or to martensitic stainless steels by thermal processes such as welding ,silver brazing ,or spray metallizing systems are acceptable for use in sour environments. provided the substrate does not exceed the lower critical temperautre during appplicaiton,in those cases in which lower critical temperature is exceeded, the component must be heat treated or thermally stress relieved in accordance with procedures that have been shown to return the base metal to the base metal hardness as specified in the standard (#which is 250hv),My Q: does applicaiton refer to applying thermal process or being used in service, if it's the former case ,how to determine that the temperature at the substrate exceeds lowr critical temperature or not,to be morre exact , is it local temperature recoreded nearby or temperature of the component . if it's the latter case then it's so rare that , for carbon steel of lower critical temperature of 723celsius , application temperature is above that .