Red color after Heat treatment

Question

Red color after Heat treatment

HaranSR (Materials)

(OP)

6 Dec 17 16:49

We are heat treating 52100 (100Cr6) material with salt quenching.
After heat treatment we are observing red colour (powder like layer) on the surface of the parts.
If i try of wipe of with cloth it gets removed, and it is not like rust.
The process are Prewash ---- 860 C / 2 Hrs --- Salt quench at 230 C / 2 hrs ----- Post wash.
Can anybody suggest what could be the reason for the red colour in the part surface.?

Tmoose (Mechanical) · Answer 1 · 2017-12-07 17:27:05

https://assets.rbl.ms/13338271/980x.gif

just kidding.

Dan T

EdStainless (Materials) · Answer 2 · 2017-12-07 18:57:41

I suspect that it is from your wash.
It may be rust that is being deposited on the surface.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, Plymouth Tube

ironic metallurgist (Materials) · Answer 3 · 2017-12-07 23:23:41

Cannot see it being anything other than rust.

"Everyone is entitled to their own opinions, but they are not entitled to their own facts."

HaranSR (Materials) · Answer 4 · 2017-12-08 08:37:55

Please refer the picture it is not rust, it is some kind of red oxidation in the surface

http://files.engineering.com/getfile.aspx?folder=b09a1c42-04b9-4a2f-b4b1-4d

djhurayt (Mechanical) · Answer 5 · 2017-12-08 13:00:09

??? isn't red oxidation on the surface RUST, ???

djhurayt (Mechanical) · Answer 6 · 2017-12-08 13:09:16

from
http://heatbath.com/2012/06/the-basics-of-molten-s...

Washing and disposal: Due to the hygroscopic nature of chloride-based quenching salt, parts should be washed soon after quenching to avoid rusting.

metengr (Materials) · Answer 7 · 2017-12-08 16:30:25

Carefully remove a sample of the residue and have it analyzed at a local materials testing lab. Easy, quick and definitive.

ironic metallurgist (Materials) · Answer 8 · 2017-12-11 21:04:21

HaranSR - Rust is a term specific to the oxidation products of iron. Iron oxides and hydroxides come in a wide variety of forms, some of which can be readily identified by appearance.

metengr - X-Ray Diffraction would be the applicable method. It is widely used by rock sample analysis labs (geology/petrology) in case your local met lab does not offer it. I have found it a very useful tool in corrosion failure investigations.

"Everyone is entitled to their own opinions, but they are not entitled to their own facts."

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Red color after Heat treatment