Yellowish Reflection on Carburized A316L
Yellowish Reflection on Carburized A316L
(OP)
I need to comprehend the reason for an unwanted yellowish appearance on stainless steel, and a cure for it.
I work on a new treatment for stainless steel used for luxury accessories (high-end watch bands). The standard steel (Aisi 316L) has a nickel content (12%) which imparts the material a bright silver-white color when mirror polished. Unfortunately the treated material has a very slight yellowish appearance (invisible to the untrained eye), which is a no-no in the industry.
The treatment diffuses carbon under the surface, for 10-20 micrometers (depending on the treatment. According to the literature available, the carbon implants itself as FCC (face centered cubic lattice, i.e in the middle of the faces of each iron cube). A lab working on this asserts that the yellowish color is not superficial and appears at some depth. Would the FCC lattice explain the shift toward yellow? Is there a way of correcting this effect? Would a transparent thin coating have the effect of correcting the reflection by interference?
I work on a new treatment for stainless steel used for luxury accessories (high-end watch bands). The standard steel (Aisi 316L) has a nickel content (12%) which imparts the material a bright silver-white color when mirror polished. Unfortunately the treated material has a very slight yellowish appearance (invisible to the untrained eye), which is a no-no in the industry.
The treatment diffuses carbon under the surface, for 10-20 micrometers (depending on the treatment. According to the literature available, the carbon implants itself as FCC (face centered cubic lattice, i.e in the middle of the faces of each iron cube). A lab working on this asserts that the yellowish color is not superficial and appears at some depth. Would the FCC lattice explain the shift toward yellow? Is there a way of correcting this effect? Would a transparent thin coating have the effect of correcting the reflection by interference?





RE: Yellowish Reflection on Carburized A316L
RE: Yellowish Reflection on Carburized A316L
RE: Yellowish Reflection on Carburized A316L
There are experts on this topic. Prof. Michaels at CWRU in Cleveland is one. Swagelok corp also is promoting a process of this type. Try their websites and publications. Your problem is new to me, but maybe someone else has encountered
the phenomenon.
RE: Yellowish Reflection on Carburized A316L
At what temperature is the carbon being diffused into the steel? Stainless steel does funny things at elevated temperatures (800-1500 F) and typical carburization treatments are conducted at that temperature.
RE: Yellowish Reflection on Carburized A316L
"colossally supersaturated". This is a new process about which there is little known.
You are correct that structure has nothing to do with color, but electron configuration does. Carbon acts as if it has a valence of four, I think. If we have any good solid state physicists around they could tell what the resulting 3d electron configuration is as carbon in solution is increased to high levels.