Relplica Metallography

in case you're planning to do some modification requiring welding to an exisitng line subjected to tempearyre nearing the border shown on B31.3 - this may inetrest u. This was from a proposal submitted by Cooperheat. Details handled by one our engineer - D. Garrido.

Actually the idea came from this forum from a lady doing a research in the effect of carburization. and we're gonna try it out.

You can find out the present condition of your steam pipeline by carrying out an in situ replica metallugraphy. This is a nondestructive  test method. You do not have to cut any sample from the pipe.

In components fabricated from plain carbon steel (API 5L Gr.B) operating at temperatures >420° C, the primary damage mechanism expected is graphitisation. The graphitisation process is essentially temperature-dependent and is not significantly affected by operating stresses, and, in weldments, usually occurs in the heat affected zone(HAZ)

Therefore, when graphitisation is of concern, a microstructure evaluation at the fine- grained HAZ/parent metal interface of weldment would be very useful. By carrying out a replica metallography across the weld we can find out the microstructural degradation.

REPLICATION PROCESS The replication process results in the production of a hard "copy" or "fingerprint" i.e. replica, of materials that captures their microstrutures for subsequent metallurgical evaluation. Replication involves the following steps:

1. Grinding and polishing the surface to be examined.
2. Etching the polished surface with an appropriate acid to develop the microstructural features.
3. Firmly applying a thin film that has been wetted and softened with a mild solvent immediately prior to application. The film is allowed to dry and is then removed.
4. The dried film is attached to a flat surface to enable readability when viewed at high magnifications using an optical microscope.

The replicas would be taken at site in a non-destructive manner under shut down condition. Because of the high temperature involved it is not possible to the test on-line. Replicas would be evaluated using Image Analyser (PC based advanced optical microscope) at our laboratory Received on Thu Jul 19 03:49:00 2001