(Graphitization occurs in:)

Comprehensive and Detailed Explanation From Exact Extract:

According to API RP 571, graphitization is a high-temperature degradation mechanism that occurs in carbon and carbon-molybdenum steels exposed for long periods at temperatures typically above 800 °F (425 °C).

In this process:

Iron carbides decompose into free graphite nodules

The steel loses strength, ductility, and pressure-retaining capability

Failures can occur without significant wall loss

Graphitization does not occur in aluminum, stainless steels, or nickel-copper alloys such as Monel.

Referenced Documents (Study Basis):

API RP 571 – Section on Graphitization

======================