carbides and graphite

Date 04-26-2012 21:25 Edited 04-26-2012 22:43

Graphite is pure carbon (chemical formula C) that cristallyzes in the hexagonal system. Color: black.
Carbides are the combination of carbon with another element, with no presence of oxygen. In the presence of oxygen the substance would be a carbonate instead of a carbide.

Example of carbides:
Calcium carbide (chemical formula Ca2C), used to make acetylene in small workshops.
Silicon carbide (chemical formula SiC), whose commercial registered trademark is Carborundum, used in grinding disks and wheels. Carborundum was a trade brand that belonged to The Carborundum Company, which has been purchased by Saint Gobain (I believe).
Tungsten carbide (chemical formula TgC), used in cutting and drilling tools.
Cr7C3 is chromium carbide, the one that appears when stainless steel passes through the sensitizing temperature, originating intergranular corrosion.

High speed steel is a high carbon steel, with a carbon content of 1 - 1,2%. Extremely hard but fragile, that's why it breaks easily when used in machining tools, which makes machinists to get upset.

There's no element whose formula is M, as you indicate. Check whether it's not Mo (molybdenum) or Mn (manganese)

Giovanni S. Crisi
Sao Paulo - Brazil

By MBSims

Date 04-27-2012 00:12

Giovanni,

I believe the "M" is simply used to indicate a "metallic" element. M7C could theoretically be Cr7C3, Ti7C3, W7C3, etc. At least that is the convention we were taught in metallurgy classes.

By DaveBoyer (*****)

Date 04-27-2012 02:07

The "M" the OP is refering to may be the "M" series of high speed steels under AISI designation. Examples would be M2, M42, M7 etc.

I am not familliar with anything with the designations Cr7C3 carbides , M7C3 and M2C carbides that the OP listed.

In the case of D2 & D3 high carbon/high chrome tool steels [1.5% carbon 12% chrome & 2% carbon and 12% chrome], the carbon and the chrome for chrome carbides. While these would be bad news in a stainless steel, they are quite wear resistant, and a good thing in an abrasion resistant tool steel.

The above mentioned D2 & D3 are NOT high speed steels. The "M" series high speed steels I mentioned do have carbon and chrome in them, and likely have chrome carbides as well. There MAY be carbides formed with some of the other elements present also, but chrome carbides do form readily.

This is an educated guess from a guy who is NOT a metalurgist.

By mohamed radwan (*)

Date 04-30-2012 07:02

Thank you all , now i'm working in steel making industry specially in rolling process , i want to know more about the material of the roll and the process and the stress related in the roll like residual stresses and distribution of carbides and graphites in the shell of the roll can any one help me with that ,