Activities under the hamon

[stezann]

Hi,
i would like to know what are the particles which display activity in the hardened part below the hamon line, i know the names are nie and nioi, but i don't know from a metallurgical point of view.
I suspect they derive from some uneveness in the hardening process, either in austenitizing or in quenching, but i don't know exactly, so i'm not able to choose the right direction to steer for promoting or suppressing.
Thank you in advance

cheers

Stefano

 

[Stacy E. Apelt - Bladesmith]

They are islands and individual crystals of martensite. Nioi are very fine crystals, and nie are coarser. When a hamon looks like a cloud, it is composed of nioi. When it looks more solid and bold, it is nie. When there are features below the hamon, it is often because the pearlite is allowed to extend through this area by the formation of ashi. The nie and nioi will then sparkle in the pearlite. This can be the most wonderful hamon.......You just don't want the pearlitic mix to reach the edge.

 

[stezann]

Thank you Stacy,
i'm having hard time figuring the cloudy habuchi (or yakiba? i must revise my terminology i guess!!!) is by contrasting on pearlite within the hardened area, since it happens well below the hamon line, near the edge and the surface.
Having no metallographic reference, i was guessing more on the line of differences in strenght of martensite and/or carbides tricks
Above the hamon i agree about martensite's islands + the same things which smoke belows.
Still my assumption could be very wrong, and i find the subject very interesting and fascinating.
The more beautiful, misterious and intriguing hamon that i think of when trying to figure it out what is happening into the steel is Nick Wheeler's clayless hamon:
Wild and active up to the roof, nevertheless austenitized in salt bath, quenched in P#50....while when it is the thickness that rules the heat mass one should expect a simple straight line like the "ring" of recalescence, which is never an active zig-zag line