scholarly journals Effect of Short-Term Low-Temperature Austempering on the Microstructure and Abrasive Wear of Medium-Carbon Low-Alloy Steel

2021 ◽  
Author(s):  
Quanshun Luo ◽  
Haijuan Mei ◽  
Matthew Kitchen ◽  
Yubi Gao ◽  
Leon Bowen
Keyword(s):  
Low Temperature ◽  
Abrasive Wear ◽  
Retained Austenite ◽  
Bainitic Ferrite ◽  
Wear Loss ◽  
Wear Property ◽  
Medium Carbon ◽  
Multiphase Microstructure ◽  
Bainitic Steels ◽  
Low Alloyed Steel

Abstract Nano-bainitic steels have attracted great attention for good wear resistance. In this research, a medium-carbon low-alloyed steel was austempered at a low temperature close to its martensite-start temperature for various times to obtain mixed microstructure of nano-bainite, martensite and retained austenite. The austempered samples were characterised comprehensively by field-emission SEM and quantitative XRD. Its two-body abrasive wear property was evaluated by sliding on a SiC abrasive disc. The results revealed the formation of initial nano-width carbide-free bainitic ferrite (BF) after austempering by 10 min, whereas the BF size and amount both increased with the austempering time. The austempered samples exhibited wear coefficients lower than the quenched martensitic sample by up to 50%. SEM and TEM observations showed wear mechanisms of micro-cutting and ploughing deformation, including the formation of a nano-laminate top layer and bending deformation in the subsurface multiphase microstructure. The decreased wear loss was attributed to the role of retained austenite in the increased plasticity. Graphic abstract

scholarly journals Characteristics of carbide-free medium-carbon bainitic steels in high-stress abrasive wear conditions

Wear ◽  
2020 ◽  
Vol 456-457 ◽  
pp. 203386
Author(s):  
Oskari Haiko ◽  
Pentti Kaikkonen ◽  
Mahesh Somani ◽  
Kati Valtonen ◽  
Jukka Kömi
Keyword(s):  
Abrasive Wear ◽  
High Stress ◽  
Free Medium ◽  
Medium Carbon ◽  
Bainitic Steels

scholarly journals Novel Approach of Nanostructured Bainitic Steels’ Production with Improved Toughness and Strength

Materials ◽  
2020 ◽  
Vol 13 (5) ◽  
pp. 1220
Author(s):  
Peter Kirbiš ◽  
Ivan Anžel ◽  
Rebeka Rudolf ◽  
Mihael Brunčko
Keyword(s):  
Electron Microscopy ◽  
Mechanical Properties ◽  
Fine Structure ◽  
Retained Austenite ◽  
Bainitic Ferrite ◽  
High Hardness ◽  
Tensile Tests ◽  
Isothermal Transformation ◽  
Impact Testing ◽  
Bainitic Steels

The tendencies of development within the field of engineering materials show a persistent trend towards the increase of strength and toughness. This pressure is particularly pronounced in the field of steels, since they compete with light alloys and composite materials in many applications. The improvement of steels’ mechanical properties is sought to be achieved with the formation of exceptionally fine microstructures ranging well into the nanoscale, which enable a substantial increase in strength without being detrimental to toughness. The preferred route by which such a structure can be produced is not by applying the external plastic deformation, but by controlling the phase transformation from austenite into ferrite at low temperatures. The formation of bainite in steels at temperatures lower than about 200 °C enables the obtainment of the bulk nanostructured materials purely by heat treatment. This offers the advantages of high productivity, as well as few constraints in regard to the shape and size of the workpiece when compared with other methods for the production of nanostructured metals. The development of novel bainitic steels was based on high Si or high Al alloys. These groups of steels distinguish a very fine microstructure, comprised predominantly of bainitic ferrite plates, and a small fraction of retained austenite, as well as carbides. The very fine structure, within which the thickness of individual bainitic ferrite plates can be as thin as 5 nm, is obtained purely by quenching and natural ageing, without the use of isothermal transformation, which is characteristic for most bainitic steels. By virtue of their fine structure and low retained austenite content, this group of steels can develop a very high hardness of up to 65 HRC, while retaining a considerable level of impact toughness. The mechanical properties were evaluated by hardness measurements, impact testing of notched and unnotched specimens, as well as compression and tensile tests. Additionally, the steels’ microstructures were characterised using light microscopy, field emission scanning electron microscopy (FESEM) and high-resolution transmission electron microscopy (HRTEM). The obtained results confirmed that the strong refinement of the microstructural elements in the steels results in a combination of extremely high strength and very good toughness.

scholarly journals Influence of Prior Martensite on Bainite Transformation, Microstructures, and Mechanical Properties in Ultra-Fine Bainitic Steel

Materials ◽  
2019 ◽  
Vol 12 (3) ◽  
pp. 527 ◽  
Author(s):  
Hui Guo ◽  
Xianying Feng ◽  
Aimin Zhao ◽  
Qiang Li ◽  
Jun Ma
Keyword(s):  
Mechanical Properties ◽  
Retained Austenite ◽  
Bainitic Ferrite ◽  
Growth Direction ◽  
Bainitic Transformation ◽  
Bainitic Steel ◽  
Bainite Transformation ◽  
Multiphase Microstructure ◽  
Microstructures And Mechanical Properties ◽  
The Impact

A multiphase microstructure comprising of different volume fractions of prior martensite and ultra-fine bainite (bainitic ferrite and retained austenite) was obtained by quenching to certain temperatures, followed by isothermal bainitic transformation. The effect of the prior martensite transformation on the bainitic transformation behavior, microstructures, and mechanical properties were discussed. The results showed that the prior martensite accelerated the subsequent low-temperature bainite transformation, and the incubation period and completion time of the bainite reaction were significantly shortened. This phenomenon was attributed to the enhanced nucleation ratio caused by the introduced strain in austenite, due to the formation of prior martensite and a carbon partitioning between the prior martensite and retained austenite. Moreover, the prior martensite could influence the crystal growth direction of bainite ferrite, refine bainitic ferrite plates, and reduce the dimension of blocky retained austenite, all of which were responsible for improving the mechanical properties of the ultra-fine bainitic steel. When the content of the prior martensite reached 15%, the investigated steels had the best performance, which were 1800 MPa and 21% for the tensile strength and elongation, respectively. Unfortunately, the increased content of the prior martensite could lead to a worsening of the impact toughness.

scholarly journals The Influence of Vanadium Additions on Isothermally Formed Bainite Microstructures in Medium Carbon Steels Containing Retained Austenite

Metals ◽  
2020 ◽  
Vol 10 (3) ◽  
pp. 392 ◽  
Author(s):  
Irina Pushkareva ◽  
Babak Shalchi-Amirkhiz ◽  
Sébastien Yves Pierre Allain ◽  
Guillaume Geandier ◽  
Fateh Fazeli ◽  
...  
Keyword(s):  
Retained Austenite ◽  
Bainitic Ferrite ◽  
High Energy ◽  
Carbon Steels ◽  
Ex Situ ◽  
Transformation Rate ◽  
Medium Carbon ◽  
X Ray ◽  
Medium Carbon Steels ◽  
Carbon Mass Balance

The influence of V additions on isothermally formed bainite in medium carbon steels containing retained austenite has been investigated using in-situ high energy X-ray diffraction (HEXRD) and ex-situ electron energy loss spectroscopy (EELS) and energy dispersive X-ray analysis (EDX) techniques in the transmission electron microscope (TEM). No significant impact of V in solid solution on the bainite transformation rate, final phase fractions or on the width of bainite laths was seen for transformations in the range 375–430 °C. No strong influence on the dislocation density could be detected, although quantitative analysis was impeded by ferrite tetragonality. A reduction in the carbon content of retained austenite Cγ that is not believed to be due to competition with VC or cementite precipitation was observed. No influence of V on the carbon supersaturation in bainitic ferrite Cb could be directly measured, although carbon mass balance calculations suggest Cb slightly increases. A beneficial refinement of blocky MA and a corresponding size effect induced enhancement in austenite stability were found at the lowest transformation temperature. Overall, V additions result in a slight increase in strength levels.

The Experimental Study on Friction and Wear Characteristics of 25Cr12Ni5Mo Hot Work Die Steels at High Temperature

2012 ◽  
Vol 157-158 ◽  
pp. 286-290
Author(s):  
Xing Guo Wang ◽  
Jiu Jun Xu
Keyword(s):  
High Temperature ◽  
Low Temperature ◽  
Abrasive Wear ◽  
Load Condition ◽  
Wear Loss ◽  
Die Steels ◽  
Low Load ◽  
Hot Work Die ◽  
Pin On Disk ◽  
Worn Surface

High temperature pin-on-disk tester heated by middle frequency induction was designed. Friction test of hot work die steels with the same composition treated under three different heat treatment conditions was carried out by the pin-on-disk tester at high temperature. The experimental temperature were 200°C、300°C、400°C、500°C, applied loads were 1kg、1.5kg、2kg、2.5kg, respectively, pin-on-disk circumrotating speed was 1000r/min for all the experiments. Morphology of worn surface and sub-surface structure were observed by optical microscope. Experimental results indicat that wear loss decrease with temperature increasing. Meanwhile, there are various growing rule under different loads, wear loss increase slightly under low load, but increase rapidly with load increasing, especially increment become larger at low temperature. Morphology of worn surface show that the two-body abrasive wear are mainly mechanism under low temperature and low load condition, oxidation wear and adherence abrasive wear are mainly mechanism under high temperature and high load condition.

scholarly journals Effects of Cr and Mo on Mechanical Properties of Hot-Forged Medium Carbon TRIP-Aided Bainitic Ferrite Steels

Metals ◽  
2019 ◽  
Vol 9 (10) ◽  
pp. 1066 ◽  
Author(s):  
Koh-ichi Sugimoto ◽  
Sho-hei Sato ◽  
Junya Kobayashi ◽  
Ashok Kumar Srivastava
Keyword(s):  
Mechanical Properties ◽  
Impact Toughness ◽  
Retained Austenite ◽  
Bainitic Ferrite ◽  
Ferrite Matrix ◽  
Total Elongation ◽  
Matrix Structure ◽  
Medium Carbon ◽  
Base Steel ◽  
Mo Additions

In this study, the effects of Cr and Mo additions on mechanical properties of hot-forged medium carbon TRIP-aided bainitic ferrite (TBF) steel were investigated. If 0.5%Cr was added to the base steel with a chemical composition of 0.4%C, 1.5%Si, 1.5%Mn, 0.5%Al, and 0.05%Nb in mass%, the developed steel achieved the best combination of strength and total elongation. The best combination of strength and impact toughness was attained by multiple additions of 0.5%Cr and 0.2%Mo to the base steel. The excellent combination of strength and impact toughness substantially exceeded those of quenched and tempered JIS-SCM420 and 440 steels, although it was as high as those of 0.2%C TBF steels with 1.0%Cr and 0.2%Mo. The good impact toughness was mainly caused by uniform fine bainitic ferrite matrix structure and a large amount of metastable retained austenite.

scholarly journals Microstructural Features of Strain-Induced Martensitic Transformation in Medium-Mn Steels with Metastable Retained Austenite/ Cechy Mikrostrukturalne Indukowanej Odkształceniem Przemiany Martenzytycznej W Stalach Sredniomanganowych Z Metastabilnym Austenitem Szczątkowym

2014 ◽  
Vol 59 (4) ◽  
pp. 1673-1678 ◽  
Author(s):  
A. Grajcar ◽  
A. Kilarski ◽  
K. Radwanski ◽  
R. Swadzba
Keyword(s):  
Electron Microscopy ◽  
Retained Austenite ◽  
Volume Fraction ◽  
Electron Backscatter Diffraction ◽  
Bainitic Ferrite ◽  
Tensile Tests ◽  
Bainitic Steels ◽  
Transmission Electron ◽  
Strain Induced Martensite ◽  
Backscatter Diffraction

Abstract The work addresses relationships between the microstructure evolution and mechanical properties of two thermomechanically processed bainitic steels containing 3 and 5% Mn. The steels contain blocky-type and interlath metastable retained austenite embeded between laths of bainitic ferrite. To monitor the transformation behaviour of retained austenite into strain-induced martensite tensile tests were interrupted at 5%, 10%, and rupture strain. The identification of retained austenite and strain-induced martensite was carried out using light microscopy (LM), scanning electron microscopy (SEM) equipped with EBSD (Electron Backscatter Diffraction) and transmission electron microscopy (TEM). The amount of retained austenite was determined by XRD. It was found that the increase of Mn addition from 3 to 5% detrimentally decreases a volume fraction of retained austenite, its carbon content, and ductility.

Effect of Retained Austenite on Impact Toughness of the Multi-Phase Bainitic-Martensitic Steel

2014 ◽  
Vol 922 ◽  
pp. 298-303 ◽  
Author(s):  
José Alberto da Cruz ◽  
Jefferson José Vilela ◽  
Berenice Mendonça Gonzalez ◽  
Dagoberto Brandão Santos
Keyword(s):  
Retained Austenite ◽  
Room Temperature ◽  
Volume Fraction ◽  
Martensitic Steel ◽  
Bainitic Ferrite ◽  
Bainitic Transformation ◽  
New Class ◽  
Bainitic Steels ◽  
Si Content ◽  
Multi Phase

The new class of bainitic steels can present toughness at room temperature greater than traditional quenched and tempered martensitic steel. This is because the microstructure of steel with high Si content (≈1.5wt%) submitted to bainitic transformation is compose of fine plates of bainitic ferrite separated by retained austenite. The inhibition of cementite precipitation leads to the improvement of toughness. The presence of cementite facilitates the nucleation of cracks. Moreover, the blocks of retained austenite are undesirable. This morphology is rather unstable and tends to transform into hard and brittle untempered martensite under the influence of small stress, contributing to a low toughness. However, it was observed in this work that the greater the volume fraction of retained austenite, the greater is the toughness (10-24 J) for multi-phase steel. The values of toughness were independent whether the retained austenite is present on film or block forms. The decrease of toughness values was observed by the tempered samples after the bainitic transformation (10-14 J). This occurred because the blocks of retained austenite decomposed into carbides, martensite and/or bainite.

Enhanced Mechanical Properties of a 0.22C-Mn-Si-Cr Low Alloyed Steel Treated by ART and Q&P Processes

2014 ◽  
Vol 1004-1005 ◽  
pp. 203-208
Author(s):  
Bai Feng An ◽  
Gu Hui Gao ◽  
Xiao Lu Gui ◽  
Zhun Li Tan ◽  
Bing Zhe Bai
Keyword(s):  
Retained Austenite ◽  
Low Carbon Steel ◽  
High Strength Steels ◽  
High Strength ◽  
Total Elongation ◽  
Alloyed Steel ◽  
Low Carbon ◽  
Multiphase Microstructure ◽  
Element Enrichment ◽  
Low Alloyed Steel

There is a currently desirable demand for high strength steels with good ductility reduce the weight of steel parts for automobile and train applications. Retained austenite in steels can improve the toughness and plasticity. The austenite reverse transformation + quenching and partitioning (ART + Q&P) process was treated on a 0.2C-Mn-Si-Cr low alloyed steel, a multiphase microstructure composed of intercritical ferrite (IF), martensite, bainite and retained austenite (RA) can be obtained in the low carbon steel. Microstructures of the steel treated by different heat treatments were characterized by SEM and XRD. Results show that the formation of RA in low alloy steel depends on the following: (1) the enrichment of the carbon and manganese in the reversed austenite during the ART step; (2) the secondary enrichment of carbon in retained austenite during the following Q&P step. High fraction of RA (14vol.%) was obtained through the two-step element enrichment treatment (ART + Q&P). Due to continuous TRIP effect of RA during the deformation, a good combination of strength and plasticity was achieved in our works: the product of strength and elongation is greater than 35 GPa•%, the tensile strength is more than 1230 MPa, the yield strength greater than 890 MPa, the total elongation is about 28.6%.

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