Martensitic microstructure is present on the thread flank and no diffusion area on the base material are present.
Microhardness indentations confirm the observation: martensite hardness is around 750 HV, instead base material is around 350 HV.
Martensite (white layer) is present on many threads.
In order to check martensite presence during RCFA, many metallographic section have been taken (etch NITAL 2%).
After in order to confirm the observaton, microhardness tests have been made.
In tutti i casi non c’è evidenza di una zona di diffusione.