Understanding and Measuring Decarburization

Understanding and Measuring Decarburization

Understanding the forces behind decarburization is the first step toward minimizing its detrimental effects. Decarburization is detrimental to the wear life and fatigue life of steel heat-treated components. This article explores some factors that cause decarburization while concentrating on its measurement. In most production tests, light microscopes are used to scan the surface of a polished and etched cross-section to find what appears to be the greatest depth of total carbon loss (free ferrite depth, or FFD) and the greatest depth of combined FFD and partial loss of carbon to determine the maximum affected depth (MAD).

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Last Updated on Tuesday, 24 March 2015 15:46

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Use of Selective Etchants to Identify Carbides in Steel

Etchants in the study - those used to darken the matrix.

Klemm’s I – Colors ferrite, limited to carbon and alloy steels Beraha’s “B0” – Darkens matrix in carbon, alloy steels, tool steels and martensitic stainless steels Beraha’s Sulfamic Acid No. 4 – Colors matrix in tool steels, martensitic and PH stainless steels

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Preparation and Characterization of Surface Treated and Coated Steels

ABSTRACT

A wide variety of surface treatments and coatings are applied to metals to enhance their performance, for example, to improve fatigue resistance, increase wear resistance, corrosion or oxidation resistance. Some of these treatments involve diffusion of one or more elements into the metal or alloy followed by post heat treatments. These processes included the familiar processes of carburizing, nitriding, and carbonitriding but also included less familiar processes such as ion nitriding and boriding. There are also a wide variety of coatings that are deposited by hot-dipping, electroless or electrolytic means, by physical or chemical vapor deposition, or by thermal or plasma spray. The technological significance of these processes is enormous.

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Microstructure of Surface Treatments, Platingsd and Coatings

Suggestions on Methods

  • Use the gentlest possible cutting method to minimize cutting damage and yield a smooth surface
  • SiC paper may be used for first grinding step
  • Start with the finest possible SiC grit size, 180-320 grit (P180 to P400), to minimize grinding damage
  • Diamond in slurry or suspension form in small sizes (< 6 μm) may become embedded in the surface of soft metals
  • Use diamond in paste form for sizes < 6 μm for soft metals
  • To minimize relief, use ChemoMet for the final step, but with higher than normal loads

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Last Updated on Monday, 11 February 2013 16:23

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Microstructure of Stainless Steels

AISI 416 - Microstructure of 416 free free-machining martensitic stainless steel in the quenched and tempered condition. Etched with Vilella’s reagent. Original at 1 100X. Note the gray 00X. elongated sulfide inclusions and the elongated “stringers” of de delta ferrite (white, see lta arrows). The matrix is tempered martensite.

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Microstructure of Ferrous Alloys

Constituents of Steel

Products of diffusion-controlled transformations.
Products of diffusionless athermal transformations.
Products of precipitation before or during solidification due to limited solid solubility, or pick-up from external sources.

Grain Boundaries

The interface between two grains where the crystal lattice changes from that of one grain to that of the other grain.
There are three types of grain boundaries in Fe-based alloys: ferrite, austenite and prior-austenite. The prioraustenite grain boundaries are those of the parent (austenite) phase before transformation. Ferrite and austenite grain boundaries are those of the product phase, although there are compositions where allotropic transformations do not occur.

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Last Updated on Monday, 11 February 2013 16:20

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Metallography of Stainless Steel and High Temperature Alloy Fasteners

Metallographic examination of longitudibally-oriented fastener specimens produces a great deal of useful information about fastener quality. Indeed, metallography is an indispensable tool for evaluating fasteners. Examination can reveal the presence of cracks or other surface flaws which may or may not, be harmful depending upon their location and nature. Metallography also can detect features associated with the manufacturing process and characterize the strenght of the fastener. All this depends upon proper selection and application of metallographic procedures.

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Last Updated on Monday, 11 February 2013 16:19

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resourcesThe articles and presentations that can be down-loaded from this web site are based upon work done by GFV while employed at Bethlehem Steel (1967-1983), Carpenter Technology (1983-1996), Buehler Ltd. (1996-2009) and Struers (2009-Present) and from the authors consulting work for companies such as, Latrobe Steel, Scot Forge, etc., and from his litigation work. GFV's bylined articles appearing in various issues of the ASM Handbook series have been listed here courtesy of ASM International, Materials Park, Ohio.

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