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Pearlite is a two-phased, lamellar (or layered) structure composed of alternating layers of ferrite (87.5 wt%) and cementite (12.5 wt%) that occurs in some steels and cast irons. During slow cooling of an iron-carbon alloy, pearlite forms by a eutectoid reaction as austenite cools below 723 °C (1,333 °F) (the eutectoid temperature). Pearlite ...
Austenite has much higher stacking-fault energy than martensite or pearlite, lowering the wear resistance and increasing the chances of galling, although some or most of the retained austenite can be transformed into martensite by cold and cryogenic treatments prior to tempering.
For a eutectoid steel (0.76% C), between 6 and 10% of austenite, called retained austenite, will remain. The percentage of retained austenite increases from insignificant for less than 0.6% C steel, to 13% retained austenite at 0.95% C and 30–47% retained austenite for a 1.4% carbon steel. A very rapid quench is essential to create martensite.
Perlite vs. Vermiculite. Perlite Perlite is a lightweight, granular material made from ground volcanic rock that is usually white in color. It is used to aerate compost and improve soil drainage ...
In carbon steel, cementite precipitates from austenite as austenite transforms to ferrite on slow cooling, or from martensite during tempering. An intimate mixture with ferrite, the other product of austenite, forms a lamellar structure called pearlite. The iron-carbon phase diagram
Austenite, also known as gamma-phase iron (γ-Fe), is a metallic, non-magnetic allotrope of iron or a solid solution of iron with an alloying element. [1] In plain-carbon steel , austenite exists above the critical eutectoid temperature of 1000 K (727 °C); other alloys of steel have different eutectoid temperatures.
The pearlite takes on longer, deeper scratches, and either appears shiny and bright, or sometimes dark depending on the viewing angle. The martensite is harder to scratch, so the microscopic abrasions are smaller. The martensite usually appears brighter yet flatter than the pearlite, and this is less dependent on the viewing angle. [12]
Seeds can be started in moistened standalone perlite or a 50-50 combination of perlite and soil, which keeps the sprouts from drying out. Perlite vs. Vermiculite Perlite and vermiculite both ...