scholarly journals Features of the formation of the structure and properties of powder steels with additives that activate diffusion processes during sintering

2020 ◽  
Vol 65 (1) ◽  
pp. 43-53
Author(s):  
L. N. Dyachkova
Keyword(s):  
Sodium Bicarbonate ◽  
Diffusion Processes ◽  
Sintering Temperature ◽  
Powder Steel ◽  
Complex Compounds ◽  
Homogeneous Structure ◽  
Crystalline Lattice ◽  
Metal Compounds ◽  
Iron Powders ◽  
Powder Steels

Effect of activating the sintering process of powder steel alloyed with nickel or chromium by grinding the initial powders and introducing alkali metal compounds was investigated. The kinetics of grinding the initial iron powders, Cr30, and a mixture of iron powders with 4 % nickel was studied. It is shown that, depending on the hardness of the powder, it is grinded in three or two stages. When grinding more hard powders, there is no stage of intensive deformation of particles and an increase in their size. Crystalline lattice defects resulting from grinding of powders accelerate diffusion processes. This reduces sintering temperature by 100–200 °С compared to the sintering temperature of steels from the initial powders, contributes to a homogeneous structure, reduces porosity by 4–17 %, and increase strength of powder steels by 1.5–1.6 times. The mechanism of the effect of sodium bicarbonate on the acceleration of diffusion of carbon, nickel and chromium into iron has been established. With the introduction of sodium bicarbonate under the action of water vapor, formed upon its decomposition to carbonate, thin oxide films are formed on iron particles, which are actively recovered in a protective-recovering atmosphere during sintering. This leads to formation of a metal contact between the particles, acceleration of the self-diffusion of iron atoms and the diffusion of alloying additives into iron by 5–7 times, depending on the sintering temperature and the amount of added additive. Sodium forms nanodispersed complex compounds of the ferritic type Na3Fe5O9 along the grain boundaries of the iron base, which provide grain refinement and the formation of a homogeneous structure. Changes in the structure of powder steel with the introduction of sodium bicarbonate cause an increase in its strength by 1.5–1.7 times. The results can be used to obtain structural products from alloyed powder steels.

Research of chromosilicated coatings on compact powder steels

2021 ◽  
pp. 47-50
Author(s):  
S.M. Gadjieva
Keyword(s):  
Chemical Elements ◽  
Diffusion Coating ◽  
Steel Corrosion ◽  
Powder Steel ◽  
The Matrix ◽  
Coating Microstructure ◽  
Steel Corrosion Resistance ◽  
Chemical And Phase Compositions ◽  
Powder Steels ◽  
Matrix Base

Microstructures, chemical and phase compositions of diffusion chromosilicated coatings on powder steels 20, 45, У8 and У10 are investigated. The presence of Cr23C6 and Cr7C3 phases with up to 0,25 % Si is shown in these coatings. The distribution of diffusing chemical elements over the depth of the coating and at the interface with the matrix base is studied. Keywords: diffusion, coating, microstructure, chromosilication, powder steel, corrosion resistance [email protected]

scholarly journals Model of Fracture, Friction, and Wear Phenomena of Porous Iron

2011 ◽  
Vol 2011 ◽  
pp. 1-16 ◽  
Author(s):  
A. A. Shatsov ◽  
I. V. Ryaposov ◽  
D. M. Larinin
Keyword(s):  
Pore Volume ◽  
Friction And Wear ◽  
Diffusion Processes ◽  
Porous Iron ◽  
Nonmonotonic Dependence ◽  
Iron Powders ◽  
Porosity Reduction ◽  
Concentration Inhomogeneity ◽  
Fracture Character ◽  
Undercooled Austenite

Mechanical and tribotechnical features of powdered materials are strongly influenced by pore volume, fracture character, impurities, alloying, concentration inhomogeneity, friction conditions, and other factors. Pores also have influence on acceleration of diffusion processes and reduce undercooled austenite resistance. Annealed in hydrogen, ultra pure iron powder was used to study porous iron features. Toughness fracture and tribotechnical features had nonmonotonic dependence from porosity different from all known dependences got from technical iron powders. Researches brought out the fact that in process of porosity reduction by pressing and annealing cycles, the average dimension of porous is changed. According to the analysis of porous structure were created models of friction, wear, and fracture of pure porous iron.

The Influence of the Sintering Temperature on the Wear Testing for Some Steels Samples Obtained by Powder Metallurgy

2014 ◽  
Vol 216 ◽  
pp. 216-221 ◽  
Author(s):  
Bebe Adrian Olei ◽  
Iulian Ştefan ◽  
Nicoleta Popescu
Keyword(s):  
Powder Metallurgy ◽  
Ball Mill ◽  
Sintering Temperature ◽  
Wear Behavior ◽  
High Energy ◽  
Wear Testing ◽  
Iron Powders ◽  
High Energy Ball Mill ◽  
Energy Ball

The objective of this research is to observe the influence of the sintering temperature on the wear testing for some steel samples elaborated by powder metallurgy technology. For obtaining the steels there were used iron powders and graphite powders. The powders were homogenized in a high energy ball mill Pulverisette 6, cold compacted and then sintered in a furnace. The sintering parameters are: the sintering temperature, T = (1050, 1100, 1150)°C and the maintaining time, t = 60 minutes. The influence of the sintering parameters on the samples wear behavior is studied using both a tribometer and a profilometer.

scholarly journals On Increasing Powder Carbon Steels Properties Using Activating Additives

2020 ◽  
Vol 25 (2) ◽  
pp. 192-201
Author(s):  
L. Dyachkova
Keyword(s):  
Mechanical Properties ◽  
Sodium Bicarbonate ◽  
Diffusion Rate ◽  
Sintering Temperature ◽  
Carbon Diffusion ◽  
Carbon Steels ◽  
Sintering Process ◽  
Activating Additives ◽  
Homogeneous Structures ◽  
Powder Carbon Steels

AbstractIn this paper, the possibility of increasing powder carbon steels properties by activation of carbon diffusion into the iron base during sintering process due to the introduction of the thermally split graphite (TSG), macromolecular compounds (MC) and sodium bicarbonate was investigated. It was found that the introduction of these additives allows obtaining homogeneous structures at a sintering temperature of 100–200 °C lower than that traditionally used for sintering of powder carbon steels. Such structures provide increased mechanical properties of powder carbon steels. The addition of sodium bicarbonate increases the diffusion rate of carbon into iron at a temperature of 950 C by 1.8 times, at 1000 °C by 1.5 times, and at 1100 °C by 1.2 times.

The Microstructure and Characteristic of 410L Stainless Honeycombs Fabricated by Extruding and Sintering

2012 ◽  
Vol 535-537 ◽  
pp. 597-600 ◽  
Author(s):  
Yun Zhou ◽  
Yu Jie Du ◽  
Xiao Qing Zuo
Keyword(s):  
Heat Capacity ◽  
Cross Section ◽  
Sintering Temperature ◽  
Cell Number ◽  
Complex Compounds ◽  
Structure Parameters ◽  
Small Particles ◽  
Silicon Iron ◽  
Eds Analysis ◽  
Powder Particles

Pure 410L powder is used to mix with an additive to prepare a powder mixed paste. 410L honeycombs are fabricated by extruding the powder mixed paste, then dried and sintered. With sintering temperature increasing from 1120°C to1150°C, the density of sintered honeycombs increasing, powder particles bind together and become grains. The structure parameters and properties of sintered honeycombs were obtained by measuring and calculating. Results show that wall thickness 0.13~0.18mm, cell number (1/in2) 350~385, clear cross section (%) 73~80, specific surface Sv(sq m/cu dm）2.68~2.85； specific heat capacity Cp(J/g.K) 0.50~0.56, heat conductivity κ(W/m.K) 11.2~12.5. SEM/EDS analysis shows that the structure of sintered honeycombs consists of matrix phase α-Fe(Cr) and small particles which are complex compounds of silicon, iron and inclusion elements distributed in matrix. Chromium oxide is formed on surface of sintered honeycombs.

Effects of Sintering Temperature on Structure and Electronic Properties of Mg0.2Zn0.8O:Al Ceramics

2011 ◽  
Vol 320 ◽  
pp. 236-239
Author(s):  
Hong Yan ◽  
Hua Wang ◽  
Shang Ju Zhou
Keyword(s):  
Grain Size ◽  
Electronic Properties ◽  
Sintering Temperature ◽  
Raw Materials ◽  
High Density ◽  
Homogeneous Structure ◽  
Second Phase ◽  
Pressureless Sintering ◽  
Nano Scale ◽  
Phase Nucleation

Mg0.2Zn0.8O:Al ceramics with high density using nano scale ZnO, MgO and Al2O3 powders as raw materials were obtained by pressureless sintering. The influence of presintering powder and sintering temperature on microstructure of Mg0.2Zn0.8O:Al ceramics were studied. The experiment indicated that presintering powder might decrease produce of the second phase nucleation. The grain size became gradually larger and density of ceramic became obviously higher from 1100°C to 1300°C, but the rising-trend became slower after 1300°C. The Mg0.2Zn0.8O:Al ceramics with high density and homogeneous structure can be made at 1300°C for

316L Stainless Honeycombs Fabricated by Extruding and Sintering

2010 ◽  
Vol 146-147 ◽  
pp. 1921-1924 ◽  
Author(s):  
Yun Zhou ◽  
Xiao Qing Zuo ◽  
Ting Zhang
Keyword(s):  
Oxide Film ◽  
Apparent Density ◽  
Sintering Temperature ◽  
Complex Compounds ◽  
Matrix Phase ◽  
Volume Shrinkage ◽  
Film Forming ◽  
Silicon Oxygen

Pure 316L powder is used to mix with an additive to prepare a powder mixed paste. 316L honeycombs were fabricated by extruding the powder mixed paste, then dried and sintered. The volume shrinkage and the apparent density of extruded honeycombs after drying and sintering were measured. The effect of sintering temperature on the volume shrinkage, the apparent density and the structure of honeycombs had been studied. The results show that the volume shrinkage and the apparent density of sintered honeycombs increase with sintering temperature from 1120°C to 1200°C , the volume shrinkage varying from 42% to 57%, and the apparent density from 1.9 to 2.9g/cm3 for 80% solids fraction. The volume shrinkage decreases and the apparent density increases with solid fractions increasing. The structure of sintered honeycombs consists of matrix phase α-Fe(Cr,Ni) , complex compounds of silicon, oxygen and inclusion elements. There is oxide film forming on surface of sintered honeycombs.

Influence of the impact sintering temperature on the structure and properties of samples from the different iron powders

2017 ◽  
Vol 28 (2) ◽  
pp. 363-374 ◽  
Author(s):  
Anatolii Laptiev ◽  
Barbara Romelczyk ◽  
Oleksandr Tolochyn ◽  
Tomasz Brynk ◽  
Zbigniew Pakiela
Keyword(s):  
Sintering Temperature ◽  
Structure And Properties ◽  
Iron Powders ◽  
The Impact

scholarly journals The Tribological Behavior of some Steel Samples Prepared by Powder Metallurgy Sintered in Microwave Field

2015 ◽  
Vol 13 ◽  
pp. 114-117
Author(s):  
Adrian Olei ◽  
Sorin Savu ◽  
Iulian Stefan
Keyword(s):  
Powder Metallurgy ◽  
Microwave Field ◽  
Sintering Temperature ◽  
Wear Behavior ◽  
High Energy ◽  
Wear Testing ◽  
Iron Powders ◽  
Heating Installation ◽  
High Energy Ball Mill ◽  
Energy Ball

The objective of this research is to observe the influence of the sintering temperature on the wear testing for some steel samples elaborated by powder metallurgy technology. For obtaining the steels there were used iron powders and graphite powders. The powders were homogenized in a high energy ball mill Pulverisette 6, cold compacted and then sintered using a Muegge type microwave heating installation. The influence of the sintering technique on the samples’ wear behavior is studied using both a tribometer and a profilometer.

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