Pearlite

About: Pearlite is a research topic. Over the lifetime, 6028 publications have been published within this topic receiving 65695 citations.

Carbide refining heat treatments for 52100 bearing steel

Abstract: The life of through-hardened 52100 anti-friction bearing components is improved if the excess carbides, undissolved during austenitization, are small and uniformly dispersed. One kind of carbide-refining heat treatment consists of 1) dissolving all carbides, 2) isothermally transforming the austenite to pearlite or bainite, and 3) austenitizing, quenching and tempering in the usual manner. Each step in this sequence of treatments was investigated, and the behavior of pearlitic and bainitic microstructures during subsequent austenitization was contrasted with the behavior of ferrite/spheroidized-carbide microstructures. It was shown that: 1) The usual hardening treatments given spheroidize-annealed bearing components result in an inhomogeneous microstructure, possibly due to the faster dissolution of carbides near austenite grain boundaries. 2) Austenitization of pearlite or bainite produces very uniform dispersions of ultra-fine carbides on the order of 0.1 µm diameter or less. 3) Specimens with ultra-fine carbides tend to have more retained austenite. 4) The rate of coarsening of ultra-fine carbides at austenitizing temperatures of 840°C and below, is slow enough so that conventional furnace heat treatments are satisfactory for producing this microstructure.

Open-source wire and arc additive manufacturing system: formability, microstructures, and mechanical properties

Abstract: The inexpensive cost and high manufacture efficient metal wire and arc additive manufacturing (WAAM) system was designed in this work. Its application potential was evaluated from the three aspects of formability, microstructures, and mechanical properties. By using compulsory cooling solution implemented in the open-source WAAM system, the complex-shaped metal parts were deposited completely with no obvious defects, such as cracks, pores, or incomplete fusion. The properties of the WAAM part were evaluated by optical microscopy (OM), scanning electron microscopy (SEM), microhardness, and microtensile test. The results indicate that the formability of metal parts fabricated by the open-source WAAM system was improved by using compulsory cooling solution. The microstructures of the WAAM part are exhibited as granular structure which consisted of the granular ferrite and the residual austenite interspersed with a little pearlite in the intermediate zone. And the average ferrite grain size of non-overlapping layer is relatively smaller than that of overlapping layer. The specimen perpendicular to the building direction exhibits a better mechanical property.

Effect of cyclic heat treatment on microstructure and mechanical properties of 0.6wt% carbon steel

Abstract: In this work an annealed 0.6 wt% carbon steel was subjected to cyclic heat treatment process that consisted of repeated short-duration (6 min) holding at 810 °C (above Ac3 temperature) followed by forced air cooling. After 8 cycles (about a total 1 h and 20 min duration of heating and cooling cycles), the microstructure mostly contained fine ferrite grains (grain size of 7 μm) and spheroidized cementite. This microstructure possessed an excellent combination of strength and ductility. The disintegration of lamellae through dissolution of cementite at preferred sites of lamellar faults during short-duration holding above Ac3 temperature, and the generation of defects (lamellar faults) during non-equilibrium forced air cooling were the main reasons of accelerated spheroidization. The strength property initially increased mainly due to the presence of finer microconstituents (ferrite and pearlite) and thereafter marginally decreased with the elimination of lamellar pearlite and appearance of cementite spheroids in the microstructure. Accordingly, the fractured surface initially exhibited the regions of wavy lamellar fracture (pearlite regions) along with dimples (ferrite regions). With increasing number of heat treatment cycles the regions of dimples gradually consumed the entire fractured surface.