The following is a reply from the reader from Part 2, which can be readhere.
allow me to respond to a couple of points.
1. You are correct. You did not
refer to nitrocarburizing in your article. It was my suggestion that the
salt-bath nitrided specimen is likely to be salt-bath nitrocarburized because the phrase “salt bath nitriding” almost always means “salt bath
nitrocarburizing.” But, if it was a true liquid nitriding process, my
comments are irrelevant.
2. Regarding carbon, if the
specimen has been nitrocarburized, the added interstitial carbon would be detected
only by surface analysis. We would expect a maximum of 3% by weight within
the compound layer, down to about 1% at 20-25 µm (probably less here
because the layer is uncharacteristically thin. 1250x?).
3. If by high hardness you mean
>58 HRC, I agree regarding the required alloying elements. However,
again – within the compound layer – a hardness of 55-58 HRC (by conversion
from HK or HV) may be obtained in unalloyed steels. But 100g loads are
far too heavy to measure such a thin layer accurately. And some hardening
does take place within the diffusion zone below the compound layer, to a
much lesser degree, as I believe Fig. 2 in the article shows down to about
0.3mm. Also, in my opinion, in addition to the hardness profile in Fig.
2, the nitride needles shown in Fig. 1 are evidence that a nitrogen
diffusion zone is present, though the caption says there is none. Perhaps
it means “none visible.”
4. Finally, and most
importantly, I repeat and agree that my comments are of minor significance
to the subject of the article. Please forgive me if it seems I am making a
“mountain out of a mole hill.” The entire motivation for any of my
comments is the assumption that the salt-bath nitrided sample is actually
salt-bath nitrocarburized, because salt-bath nitrocarburizing processes are
routinely referred to as salt-bath nitriding processes in industry. If it
is a salt-bath nitrocarburized specimen, I felt it important to point out
that the photo and some of the statements are not necessarily
representative of salt-bath nitrocarburizing.
much for your willingness to “banter” on this subject and certainly for your