The alloy database says on Cu alloying of Fe (http://www.steeldata.info/inclusions/demo/help/ferro.html#Cu)
" The presence of more than 0.2% Cu in steel produces a characteristic checking on forging surfaces.... preferential oxidation of iron near the metal surface leaves a copper-enriched zone containing the low-melting e phase on grain boundaries. In severe cases, the steel will be hot short and unworkable. Three solutions to this well-known problem are: ... (3) add nickel or cobalt in amounts equal to about 1/3 to 1/2 the copper content as these metals raise the melting point of the copper phase. The third solution is most common, ... As nickel content rises, so does the allowable forging/rolling temperature, although a practical limit in nickel content is signaled by the formation of a protective glaze at temperatures above 1280 C (2150 F)"
The reference to the page is " Paul Deeley, Konrad J.A. Kundig, and Howard R. Spendelow, Jr., FERROALLOYS & Alloying Additives HANDBOOK, Shieldalloy Corp. "
My questions are
- Is the "so-called glaze "some sort of intermetallic? Then why it is called protective? Is it for being impervious to Oxygen, or being shiny or something else?
- What is composition of the "glaze", Which I presume, to be intermetallic?
- Why further addition of Ni is not allowed and what does the formation of glaze indicate in terms of limiting compositiion of solubility of Ni or Cu in steel?
I have found no satisfactory answer from the phase diagram of Cu-Ni-Fe. Perhaps I have missed something.
Article Cu-Fe-Ni (copper-iron-nickel)
Dear Sumit Bhowmick thank you very much for your very interesting technical question. Although we are inorganic chemists, I'm far from being a proven expert in this field of research. Our area of expertise is organometallic chemistry. Thus all I can do for you right now is to suggest to you some potentially useful references on this topic. When you ask "Is the "so-called glaze "some sort of intermetallic?" I would say that protecting layers on metal surfaces are often not intermetallic phases but contain e.g. oxygen or fluorine. Oxygen can be present e.g. in the form of the corresponding metal oxides or carbonates. For example, during our work with elemental fluorine we used cylinders made of so-called Monel with is a nickel-copper-iron alloy. The inside surface of the cylinders was protected against the aggressive fluorine through a thin layer of nickel fluoride.
Getting back to your original question I suggest that you have a look at the following potentially useful article entitled
Lead Free Cu-Containing Frit for Modern Metallic Glaze
Article Lead Free Cu-Containing Frit for Modern Metallic Glaze
Fortunately this article is freely available as public full text on ResearchGate. In this case the formation of a metallic-looking glaze is due to the presence of CuO crystallites and Cu metallic particles.
Also please see the following relevant article entitled
High-Pressure Cold-Sprayed Ni and Ni-Cu Coatings: Improved Structures and Corrosion Properties
Article High-Pressure Cold-Sprayed Ni and Ni-Cu Coatings: Improved S...
In this article it is mentioned that nickel-containing protective glaze layers also comprise oxygen (nickel oxide).
I hope this helps in your analysis.
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