Papers by Keyword: Quenching

Abstract: The present work is a contribution in investigating the effect of heat treatment on microstructure, hardness and friction wear of A105N steel. Samples of 25x25 mm2 cross-section and 15mm thickness have been prepared from the as-received material and then heat-treated. The samples were austenitized at 1050°C for 60 minutes followed by water quenching, then tempered at 500 and 700°C for 120 minutes. Microstructural changes and their effect on the wear resistance and hardness were investigated according to the applied heat treatments. The main results show that after quenching the structure is mostly composed of quenched martensite, which confers high hardness and friction resistance to the steel. While the tempered structure is composed of tempered martensite and ferrite. As the temperature rises to 700°C, the tempered martensite decreases and is fully transformed to ferrite and cementite. A good wear resistance expressed by a low friction coefficient and a low wear rate is achieved by tempering at 500°C.

Abstract: The aim of this work was to study the influence of quenching and partitioning temperatures combined with various levels of Mn and Ni contents on the austenite stabilization along the quenching and partitioning (Q&P) cycle. Three steels with 2 wt.%, 4 wt.% and 6 wt.% manganese and one steel with 2 wt.% nickel content were investigated. Phase transformation temperatures and critical cooling rates were obtained experimentally using dilatometer for each alloy. Q&P cycles with different quenching and partitioning temperatures were also done in dilatometer, thus, allowing monitoring of the expansion/contraction during the whole Q&P cycle. Microstructure characterization was performed by means of a Scanning Electron Microscope and X-Ray Diffraction to measure retained austenite content. It was found that, strongly depending on the Q&P conditions, austenite stabilization or decomposition occurs during partitioning and final cooling. In case of high partitioning temperature cycles, austenite reverse transformation was observed. Certain cycles resulted in a very effective austenite stabilization and interesting microstructure.

Abstract: We have been investigating the series of P doped Ca₂SiO₄ (C₂S) using Eu²⁺ or Eu³⁺ as activator with various colors. The crystal structure of C₂S is particularly easily controlled by heating because the established polymorphs of C₂S are, in the order of increasing temperature, γ, β, α’_L, α’_H, and α. In order to control the crystal structure, the phosphors were synthesized and then annealed at temperatures 1473 K-1773 K. The crystal structures and PL properties were compared between slow cooling and quenching (cooled in water). We found unique phenomena when the phosphors were treated by quenching process. In the case of (Ba_1-xCa_x)₂(Si_0.94P_0.06)O₄:Eu³⁺ ( 0.25 ≤ x ≤ 1), color emission changed from red to blue-white for the phosphor with a high concentration of Ba and quenched at 1773 K. In general, Eu³⁺ doped phosphors showed the red emission color in any host materials. However, Ba-included and quenched-treatment phosphors emitted a bright white color. The mechanism and relationship between the PL property and crystal structure were characterized carefully using X-ray diffraction, electron microscope and X-ray absorption fine structure.

Abstract: During the operation of porcelain stoneware sometimes there is a type of defects associated with crumbling from the edge of tile. In addition, cracks occur when a small object is fallen and during transportation of the products. Compared to conventional ceramic floor tiles, porcelain stoneware has increased strength, which explains its high price. The brittle failure is most likely, due to the hardening of glassy phase of tiles during cooling stage of the firing process. As a rule, the quenching temperature depends on the chemical composition of the glassy phase formed during firing. Both the phase and chemical composition of porcelain stoneware, and the chemical composition of the glassy phase are determined.

Abstract: The structure of martensite obtained by quenching steel under the action of a constant magnetic field was studied. The kinetic changes of the martensitic transformation, caused by the action of a magnetic field, are expressed in the structure by an increase in the dispersity of the transformation products. Samples of steels C45, 100CrMn6 and 30HGSA were investigated. Dispersity was evaluated statistically in images obtained on light and electron microscopes. The specific surface area was measured and the parameters of the surface relief caused by martensitic transformation were studied. Experimental data show that after quenching in a magnetic field, a decrease in the volumetric strain of the transformation, an increase in the dispersity of packets of martensitic crystals and components of the packets are observed. It is concluded that an increase in dispersion and a fragmentation of the structure of martensite are mainly the result of multiplicative nucleation.

Abstract: Development of an optimal technology of heat treatment for blanks of the casing pipe made of steel 40H (GOST 4543) is used in the oil and gas industry for casing. It is accompanied by quenching in various environments to ensure guaranteed obtainment of the required mechanical characteristics. These characteristics are specified in GOST 632-80 and met in order to improve the properties of the 40H steel.

Abstract: Quenching process is the most important step in steel heat treatment as this process will determine the properties of the steel such as strength and hardness. Different cooling rate and thermal conductivity provided by the quench medium affect strongly to the mentioned steel properties. Recently, studies for nanoparticle added in the quench medium are developing rapidly. This nanoparticle added fluid is known as nanofluid and could affect the thermal property of the quench medium which ultimately changes the properties of the steel. The nanoparticle composition in nanofluid will affect its thermal property. In this research, carbon was used as the nanoparticle. The composition variations were 0.1, 0.3, and 0.5 weight percent in 100 ml distilled water. Pure distilled water was also used as a comparison control. Planetary ball-mill were utilized for 15 hours at 500 rpm to produce nanosized carbon particle. Field-Emission Scanning Microscope (FE-SEM) and Energy Dispersive X-Ray (EDX) were used to check the particle size, shape and purity of the carbon nanoparticles. These nanofluids were then used to quench S45C carbon steels samples annealed at 1000°C for 1 hour. Samples were attached with a thermocouple which connected to temperature data logger to observe the cooling rate of the quench medium. The quenched samples were be tested to get the information of hardness and metallography analysis for supporting data.

Abstract: In this article the experimental data of the hardness and wear resistance of chrome-manganese steels 35H3G2F and 35HGF, which are cemented in a highly active paste-like carburizer and hardened at various temperatures, are presented. Cementation and high temperature carbonitriding of these steels leads to a high content of the carbide phase in the diffuse layers and an increase of hardness and wear resistance. The effect of carbides on the hardenability of diffuse layers are investigated. The hardening temperature ranges of these steels and the effect of alloying elements on hardness are established. The mechanism of the phase formation of the highest hardness structures is described. The carbides influence on the wear mechanism of cemented in various modes steels is studied.

Abstract: High-carbon high-strength JIS-SUJ2 bearing steel is one of the alloys used as rolling contact applications which need high wear resistance. This high hardness material is broken from non-metallic inclusions under fatigue stress. In this work, we developed a new observation method “fracture surface etching (FSE)” in order to observe the material microstructure on the fracture surface. We succeeded to draw clear grain boundaries on the fracture surfaces and closely observed the material microstructure around the crack origins by the FSE method. We concluded that the crack initiation area boundary is not formed by only the grain boundary, and the grain size around the Al2O3 inclusion on the fracture surface was similar to that of the flat surface which does not have inclusions before fatigue testing.

Abstract: The relationship between the phase composition and the Young’s modulus in quenched PT-7M, Ti-6Al-7Nb, BT16 titanium alloys has been studied using the structural analysis, thermodynamic calculations in the Thermo-Calc software and micro-indentation. It is found that the nature of the change in the Young’s modulus in the investigated titanium alloys after quenching from the two-phase α+β-region depends on the chemical composition of the alloy, which determines the nature of the observed metastable phases (α', α", ω, β). The correlation between the extreme change in the Young’s modulus from the quenching temperature and the so-called interatomic bonding force (F_b) calculated from the electronic structure parameters of the α, α', β phases was shown for the Ti-6Al-7Nb alloy. The relationship between the limits of the Young’s modulus of the investigated alloys during quenching with the level of their alloying with α-and β-stabilizers is shown.