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Heat Treatments and Surface Hardening of Small Weapon Components
Published in Jose Martin Herrera Ramirez, Luis Adrian Zuñiga Aviles, Designing Small Weapons, 2022
Jose Martin Herrera Ramirez, Luis Adrian Zuñiga Aviles
Another aspect that the diagram in Figure 8.1 shows is the presence of the (pearlite + ferrite) mixture in the iron-rich region (hypoeutectoid steels), as well as the presence of the (pearlite + cementite) mixture in the carbon-rich region (hypereutectoid steels). Pearlite is a microconstituent with lamellar structure composed of alternating layers of ferrite (α−Fe) and cementite (Fe3C), which were described in Chapter 7 (Section 7.4, Figure 7.3). Detailed description and morphology of steel phases will be shown in subsequent sections.
Iron and steel
Published in William Bolton, R.A. Higgins, Materials for Engineers and Technicians, 2020
All of the foregoing heat-treatment processes produce a microstructure in the steel which is basically pearlitic. By this, metallurgists mean that the structure contains some pearlite (unless, of course, the steel is dead mild). Thus, a hypo-eutectoid steel will contain ferrite and pearlite, a eutectoid steel only pearlite, and a hyper-eutectoid steel cementite and pearlite. Figure 11.13 summarises the temperature ranges at which these treatments are carried out, and also indicates the carbon contents of the steels most commonly involved in the respective processes.
Microconstituent Diagrams and Microstructures
Published in Joseph Datsko, Materials Selection for Design and Manufacturing, 2020
Pearlite is a mechanical mixture of ferrite and cementite, usually in lamellar form, and of eutectoid composition. The term “mechanical mixture” means that the two phases are physically distinct and can actually be mechanically separated, as opposed to a chemical mixture, where the phases lose their individual identities. The expression “of eutectoid composition” is relevant because it is not necessary for a steel to have a 0.8% carbon content in order to have a microstructure that consists of only the one microconstituent, pearlite. For example, both a 0.8% C plain carbon steel and a 0.4% C alloy steel that contains 1.25% Mo are 100% pearlite (see Figure 4–5). That is, their microstructure is entirely pearlite.
Diffusion behaviour in high-chromium cast iron/low-carbon steel bimetals
Published in Philosophical Magazine Letters, 2019
Yongcun Li, Ping Li, Mengying Gong, Weiping Tong
The results of the EMPA analysis near the interface of the Cr21-HCCI and LCS are shown in Figure 2. Figure 2a shows the secondary electron image: the left side denotes the LCS side and the right side the Cr21-HCCI. At 1300°C, Cr- and Mo-atoms cannot diffuse into the LCS through tetrahedral or octahedral spaces in the austenite owing to their large atomic radius and, asa cosequence, they were not detected in the LCS side, as shown in Figure 2b and c. The smaller atomic size of C atoms, compared to those of the Cr- and Mo-atoms, enabled their long-range diffusion at high temperatures. As Figure 2d shows, the content of pearlite significantly decreased from the interface to the left side of the figure; in other words, the C atoms have a distinct gradient distribution. This can be explained by the C atoms in the HCCI diffusing into the LCS. At 1300°C, the C-content in the LCS austenite increased as the diffusion proceeded and reached a near-eutectoid composition. The austenite, an eutectoid component, transformed into pearlite during the subsequent cooling process. It should be emphasised that this is an essential difference from our previous work [10], where we found an uphill diffusion phenomenon in the diffusion couple consisting of HCCI and LCS because the C atoms diffused from a low-concentration zone (LCS) to a high-concentration zone (HCCI).
Effect of Matrix Microstructure on Abrasive Wear Resistance of Fe–2 wt% B Alloy
Published in Tribology Transactions, 2019
Yanliang Yi, Jiandong Xing, Wei Li, Yangzhen Liu, Baochao Zheng
The main conclusions are as follows: Fe–2 wt% B alloy mainly consists of a metallic matrix (pearlite and martensite), M2B, and M23(C, B)6. The cooling rate has a great influence on the matrix microstructure. Pure pearlite occurs at a cooling rate of 0.05 °C/s, and pure martensite forms when the cooling rate exceeds 0.3 °C/s.With the same sliding distance, compared to pearlite, martensite can better support M2B against fracture and results in greater abrasion resistance of Fe–2 wt% B alloy.With an increase in sliding distance, the wear rate of Fe–2 wt% B alloy first increases slightly and then increases rapidly. The corresponding wear mechanism is that the M2B is steadily scraped off until a critical sliding distance of 6.06 m is reached, after which the neighboring M2B fractures.Fe–2 wt% B alloy with martensite matrix has better abrasion resistance than Cr26 and M2.
Corrosion inhibition of ferrite bainite AISI1040 steel in H2SO4 using biopolymer
Published in Cogent Engineering, 2021
P.R. Prabhu, Deepa Prabhu, Ayush Chaturvedi, Priyank Kishore Dodhia
Figure 3(a) shows the microstructure of AISI1040 steel in as-received condition. The steel shows ferrite and lamellar pearlite grains. The steel rods might have undergone air cooling, resulting in the formation of fine grains. Figure 3(b) shows the microstructure of steel in the normalized condition. The microstructure displays fine and lamellar pearlite and proeutectoid ferrite. The interlamellar distance in normalized pearlite is smaller when compared to the as-bought steel as a result of normalizing heat treatment. Fine pearlite enhances the mechanical properties of the steel. Figure 3 (c) shows the duplex structure in the steel containing ferrite and feathery bainite. The steel is heated in between lower and upper critical temperatures of the iron carbide phase diagram where homogeneous austenite is not formed. During this process, the pearlite of as-received steel converts into austenite first and proeutectoid ferrite remains unchanged. When the steel is quenched from this temperature, the austenite converts to lower temperature structures like bainite. When the steel is quenched in subcritical temperatures (350°C), the cooling curve enters the bainite zone. When austenite is cooled in this temperature range, carbon atoms redistribute in austenite. Low carbon regions transform to ferrite by diffusionless processes and result in fine needles of ferrite. As time passes, carbon diffuses out and precipitates in the form of fine carbides, the arrangement of carbides here is not in the form of lamellar structure. In this study, the steel displays upper or feathery bainite along with proeutectoid ferrite.