Comportement au revenu d'un acier du type Z80CDSV8.2.1.1 pour cylindres de laminoirs à chaud

1996 ◽  
Vol 84 ◽  
pp. 3-12
Author(s):  
H. Djebaïli
Keyword(s):  
Magnetic Measurements ◽  
Residual Austenite ◽  
Progressive Increase ◽  
Continuous Heating ◽  
Preliminary Treatment ◽  
Hardness Testing ◽  
Physical Methods ◽  
The Matrix ◽  
Primary Carbides ◽  
Hot Hardness

Transformations in Cr-Mo-Si steels with a specific addition of Vanadium have been characterized precisely as well as their effect on the hardness of the materials. A preliminary treatment in the austenitic field leads to a limited enrichment of the matrix as well as temperature is less than 1050°C : only M3C and M23C6 carbides may then be dissolved. On the contrary, the dissolution of M7C3 and MC carbides is observed over 1100°C but is only partial even after treatment at 1150°C. After quenching from three distinct temperatures (1050-1100 and 1150°C), the microstructure consists of martensite, residual austenite and primary carbides (mainly M7C3 and MC type) ; different tempering treatments have been performed (isochronal, isothermal or on continuous heating) using various physical methods (dilatometry, DTA and magnetic measurements, TEM observations and hot hardness testing). According to the maximum θR temperature reached, the following structural evolutions were observed :•ε carbide precipitates at θR < 250° C in the a’ matrix, then M3C carbide forms between 250 and 350°C which transforms in M7C3 carbide from 450 to 500°C. At the same time (300- 500°C) a secondary hardening occurs linked to the formation of very fine V4C3 carbides : a progressive increase in hot hardness is observed while holding isothermally at 300-450°C.•From 450 to 600°C, the residual austenite is destabilized owing to the precipitation of small carbides in α'/γ interfaces and may be transformed on cooling either in bainite or secondary martensite. On the other hand that impoverished austenite may be transformed in (α + carbides) between 600-700°C. Besides in the same temperature range, M6C and M23C6 may be formed at the expense of fine M7C3 carbides previously formed.

scholarly journals Examination of Heat Treatment on the Microstructure and Wear of Tool Steels

2019 ◽  
Vol 2 (2) ◽  
pp. 87-92
Author(s):  
Enikő Réka Fábián ◽  
László Tóth ◽  
Csenge Huszák
Keyword(s):  
Wear Resistance ◽  
Retained Austenite ◽  
Cryogenic Treatment ◽  
Residual Austenite ◽  
Tool Steels ◽  
Austenite Content ◽  
The Matrix ◽  
Primary Carbides ◽  
Matrix Hardness ◽  
Multiple Tempering

Abstract The microstructure of the investigated X153CrMoV12 grade tool steel in delivered condition consisted of spheroidal matrix and primary carbides. The primary carbides were not dissolved under austenitisation time on either 1030°C or 1070°C. The microstructure and abrasion resistance of the steel changed due to quenching from different austenitisation temperatures. After conventional quenching from the higher austenitising temperature, there is more residual austenite in the steel than at quenching from the lower austenitisation temperature, which decreased the wear resistance. As a result of quenching from 1070°C followed by a multiple tempering process around 500 to 540°C, the retained austenite content is reduced and finely dispersed carbides are precipitated in the matrix, resulting in a higher matrix hardness and an increased wear resistance. After cryogenic treatment, the residual austenite content decreases compared to the conventional process, which leads to an increase in hardness and wear resistance.

The Relationship Between Magnetism and Microstructure of Ethylene Pyrolysis Furnace Tubes after a Long-term Service

2018 ◽  
Vol 24 (5) ◽  
pp. 478-487 ◽  
Author(s):  
Jingfeng Guo ◽  
Tieshan Cao ◽  
Congqian Cheng ◽  
Xianming Meng ◽  
Jie Zhao
Keyword(s):  
Saturation Magnetization ◽  
Outer Region ◽  
Cr Content ◽  
Pyrolysis Furnace ◽  
The Matrix ◽  
Furnace Tube ◽  
Primary Carbides ◽  
The Relationship ◽  
Very High

AbstractThe magnetism and microstructure of Cr25Ni35Nb and Cr35Ni45Nb alloy tubes after 5 years of service were investigated in this paper. The saturation magnetization of the Cr25Ni35Nb alloy tube in the thickness direction is more than 20 emu/g, and the tube becomes ferromagnetic. The inner and outer walls of Cr35Ni45Nb alloy tubes also become ferromagnetic. But the saturation magnetization of the Cr35Ni45Nb alloy tubes approaches to zero in the center zone. The primary carbides M7C3 and NbC are changed into M23C6 and G phase at the outer region of the furnace tube. However, the M23C6-type carbides were replaced by carbon-rich carbides M7C3 at the carburization zone. Cr-depleted zones are formed at the inner and outer walls of the furnace tubes owing to oxidation. Carburization and oxidation reduce the Cr content of the matrix. Accordingly, the saturation magnetization is very high at the carburization zone and Cr-depleted zone. The magnetism of Cr25Ni35Nb and Cr35Ni45Nb alloy tubes has a high correlation with the Cr content of the matrix. Carburization and oxidation are the main reasons that make the paramagnetic ethylene pyrolysis furnace tube change to ferromagnetic.

The Effect of Surface Active Substances on the Mechanical Properties of a Copper-Matrix Nanocomposite

2019 ◽  
Vol 945 ◽  
pp. 493-497
Author(s):  
Y. Shchetinin ◽  
Y. Kopylov ◽  
A. Zhirkov
Keyword(s):  
Mechanical Properties ◽  
Thermal Conductivity ◽  
Composite Material ◽  
Carbon Nanostructures ◽  
Hot Isostatic Pressing ◽  
Copper Matrix ◽  
Planetary Mill ◽  
Preliminary Treatment ◽  
Nanostructured Composite ◽  
The Matrix

The presented work reviews the research in the field of production of nanostructured composite materials based on copper, reinforced with carbon nanostructures. Particular attention is paid to the use of composites with high thermal conductivity as structural materials. The method of manufacturing a composite material based on copper is described in detail: modes of preliminary annealing, pre-pressing, hot isostatic pressing. The characteristics of the matrix and alloying components are given, and also preliminary treatment of copper powder and carbon nanotubes is described. Different mechanisms of component mixing are considered, the process of mechanical alloying in a planetary mill is described in detail, the results of measuring the thermal conductivity of samples are given. The mechanical characteristics of the samples are considered in detail: ultimate strength, yield strength, elongation. The degree of influence of surfactants on the uniformity of the distribution of alloying components and the mechanical properties of the composite material is determined.

scholarly journals The Effect of Thickness on the Properties of Laser-Deposited NiBSi-WC Coating on a Cu-Cr-Zr Substrate

Photonics ◽  
2019 ◽  
Vol 6 (4) ◽  
pp. 127
Author(s):  
Yury Korobov ◽  
Yulia Khudorozhkova ◽  
Holger Hillig ◽  
Alexander Vopneruk ◽  
Aleksandr Kotelnikov ◽  
...  
Keyword(s):  
Wear Resistance ◽  
Matrix Material ◽  
Copper Substrate ◽  
Thin Layers ◽  
Laser Deposition ◽  
The Matrix ◽  
High Level ◽  
Primary Carbides ◽  
Matrix Powder ◽  
Wear Tests

Ni/60WC coatings on copper substrate were placed via laser deposition (LD). A structural study was conducted using electron microscopy and a microhardness evaluation. Two body abrasive wear tests were conducted with a pin-on-plate reciprocating technique. A tool steel X12MF GOST 5960 (C-Cr-Mo-V 1.6-12-0.5-0.2) with a hardness of 63 HRC was used as a counterpart. The following results were obtained: Precipitation of the secondary carbides takes place in the thicker layers. Their hardness is lower than that of the primary carbides in the deposition (2425 HV vs. 2757 HV) because they mix with the matrix material. In the thin layers, precipitation is restricted due to a higher cooling rate. For both LD coatings, the carbide’s hardness increases compared to the initial mono-tungsten carbide (WC)-containing powder (2756 HV vs. 2200 HV). Such a high level of microhardness reflects the combined influence of a low level of thermal destruction of carbides during laser deposition and the formation of a boride-strengthening phase from the matrix powder. The thicker layer showed a higher wear resistance; weight loss was 20% lower. The changes in the thickness of the laser deposited Ni-WC coating altered its structure and wear resistance.

Microstructure and Properties of Surface Nanostructured Copper

2011 ◽  
Vol 328-330 ◽  
pp. 1606-1609
Author(s):  
Wan Ming Lin ◽  
Yin Hui Wei ◽  
Li Feng Hou
Keyword(s):  
Copper Plate ◽  
Surface Mechanical Attrition Treatment ◽  
Hardness Testing ◽  
Surface Layers ◽  
Materials Properties ◽  
Transmission Electron ◽  
Mechanical Attrition ◽  
The Matrix ◽  
Novel Method ◽  
Potentiodynamic Anodic Polarization

Surface nanocrystallization (SNC) is a novel method for improving materials properties. Nanostructured surface layers of about 20 μm thickness were produced in copper plate samples by means of surface mechanical attrition treatment (SMAT). The behaviors of the SMAT samples were investigated by using transmission electron microscopy (TEM), Vickers hardness testing and potentiodynamic anodic polarization tests. The experimental results showed that the longer the peening time was performed on the copper pate samples, the thicker the deformation layers formed. The microhardness results for the top surface layer of the copper plate sample are 1.723 GPa and 1.752 GPa for 45 and 60 min, respectively, which are about two times higher than that of the matrix. The primary passivate potential of nanocrystalline copper was more negative than that of coarse-grain copper.

Interface Versus Diffusion Controlled Growth in Nanocrystallization Kinetic Studies

1995 ◽  
Vol 398 ◽  
Author(s):  
N. Clavaguera ◽  
M.T. Clavaguera-mora
Keyword(s):  
Amorphous Alloys ◽  
Isothermal Annealing ◽  
Kinetic Studies ◽  
Crystal Growth Rate ◽  
Continuous Heating ◽  
Subsequent Growth ◽  
Scanning Calorimetry ◽  
Nucleation Frequency ◽  
Diffusion Controlled ◽  
The Matrix

ABSTRACTNanocrystallization by heat treatment of initially amorphous alloys occurs for high nucleation frequency I and low crystal growth rate u values. Calorimetrie data extracted, for instance, from differential scanning calorimetry are normally presented by the dependence of the crystallized fraction x, on: i) x=x(T,t) when obtained under isothermal annealing at temperature T as a function of time t; ii) x=x(τ,β) when obtained under continuous heating at a scan rate β as a function of temperature. Theoretical analysis of the crystallization kinetics is presented which accounts for nuclei either pre-quenched or created by homogeneous nucleation whose initial steps of growth are controlled by the interface formation between the nanocrystals and the matrix and subsequent growth is limited by diffusion.

Effect on Microstructure and Hardness of Plunger Piston of Fe-Based Composite Coating by Laser Cladding

2011 ◽  
Vol 189-193 ◽  
pp. 830-833
Author(s):  
Yong Tao Zhao ◽  
Wen Xue Li ◽  
Jun Wei Zhou
Keyword(s):  
Wear Resistance ◽  
Laser Cladding ◽  
Second Phase ◽  
Micro Hardness ◽  
Hardness Testing ◽  
Matrix Metal ◽  
Cladding Layer ◽  
Hard Particles ◽  
The Matrix ◽  
Metal Microstructure

The laser cladding of Fe power technology was used to repair worn plunger piston surface. The microstructure of cladding layer, binder course and the matrix were observed by OM and SEM. Besides, the micro-hardness of different zones was measured through micro-hardness testing. The results show that the matrix metal microstructure of plunger piston is made of ferrite and austenite. By laser cladding Fe-based power on base metal, the cladding layer grain is fine and uniform, grain growth has obvious direction and finally become dendrites oriented, the microstructure of cladding layer is both second-phase hard particles and Fe-based solutes. The combination between matrix and cladding layer is smooth, belong to metallurgy bonding. The hardness of cladding layer is higher than that of other parts in three parts, the max value of micro-hardness is about 1250HV, it can agree with wear resistance need of plunge piston surface.

Magnetic and Structural Properties of Nanocomposite ZnO-Fe3O4 Films Prepared by Solid-State Synthesis

2014 ◽  
Vol 215 ◽  
pp. 158-162
Author(s):  
Liudmila E. Bykova ◽  
V.G. Myagkov ◽  
I.A. Tambasov ◽  
O.A. Bayukov ◽  
Victor S. Zhigalov ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Solid State ◽  
Photoelectron Spectroscopy ◽  
Magnetic Measurements ◽  
X Ray Diffraction ◽  
Simple Method ◽  
Physical Methods ◽  
X Ray ◽  
Scanning Electron

A simple method for obtaining ZnO-Fe3O4 nanocomposites using solid-state reaction Zn + 3Fe2O3 ZnO + 2Fe3O4 is suggested. An analysis of the characteristics and properties of ZnO-Fe3O4 nanocomposites was carried out by a combination of structural and physical methods (X-ray diffraction, scanning electron microscopy, photoelectron spectroscopy, Mössbauer measurements, X-ray fluorescent analysis, and magnetic measurements). The magnetization of the hybrid ZnO-Fe3O4 films is equal to 440 emu/cm3. The resulting Fe3O4 nanoparticles are surrounded by a ZnO shell and have sizes ranging between 20 and 40 nm.

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