scholarly journals THERMODYNAMIC MODEL OF AERODYNAMIC SOUND HARDENING METHOD

2020 ◽  
Vol 4 (53) ◽  
pp. 65-69
Author(s):  
Anatoliy N. JIGALOV ◽  
◽  
Valeriy K. SHELEG ◽  
Dmitriy D. BOGDAN ◽  
◽  
...  
Keyword(s):  
Impact Toughness ◽  
Hard Alloy ◽  
Thermodynamic Model ◽  
Thermodynamic System ◽  
Initial Structure ◽  
Hard Alloys ◽  
Resonant Amplitude ◽  
Aerodynamic Sound ◽  
Wave Effects ◽  
The Impact

As a result of scientific research, a method of aerodynamic sound hardening (ADH) has been developed and patented, which makes it possible to achieve improved properties of hard alloys by reducing their defectiveness, improving the homogeneity of the structure. The physics of the ADH process is that the hardened product is preheated to an acceptable temperature at which the hard alloy does not lose the plasticity and hardness acquired during manufacture. Then the product is exposed to sound frequency waves, reduced in the range of 140...160 Hz into a resonant state, in which the formation of a resonant amplitude increased by several hundred times occurs. The article gives a description of the essence of the created ADH method. The dependence for determining the action energy on a hardened solid by ADH is provided. A thermodynamic model of the ADH method is presented, based on energy thermal and wave effects on the hardened structure. On the basis of the thermodynamic explanation, the ADH method is reduced to a change in the initial structure of the hard alloy under the influence of temperature and wave resonant energy fluxes on it, through which activating and dissipative processes of energy outflow are excited in the hardening object in the mode of an open thermodynamic system. In addition, the quasi-static process of wave energy transfer, carried out in a non-equilibrium medium, significantly exceeds the relaxation time of the strengthening system. When hardening by ADH, the impact toughness increases by 19–23 % in hard alloys, while the values of impact toughness equal to 39.54–42.05 kJ/m2 are achieved, the hardness according to the HRC parameter increases by 3.0–5.2 %.

scholarly journals Laser Surface Hardening of Ni-hard White Cast Iron

Metals ◽  
2020 ◽  
Vol 10 (6) ◽  
pp. 795
Author(s):  
Samar Reda Al-Sayed ◽  
Ahmed Magdi Elshazli ◽  
Abdel Hamid Ahmed Hussein
Keyword(s):  
Wear Resistance ◽  
Cast Iron ◽  
Impact Toughness ◽  
Surface Hardening ◽  
White Cast Iron ◽  
Laser Surface ◽  
Hard Alloys ◽  
The Core ◽  
Laser Surface Hardening ◽  
The Impact

Laser surface treatment on two different types of nickel–chromium white cast iron (Ni-hard) alloys (Ni-hard 1 and Ni-hard 4) was investigated. Nd:YAG laser of 2.2-kw with continuous wave was used. Ni-hard alloys are promising engineering materials, which are extensively used in applications where good resistance to abrasion wear is essential. The conventional hardening of such alloys leads to high wear resistance nevertheless, the core of the alloy suffers from low toughness. Therefore, it would be beneficial to harden the surface via laser surface technology which keeps the core tough enough to resist high impact shocks. A laser power of different levels (600, 800 and 1000 Watts) corresponding to three different laser scanning speeds (3, 4 and 5 m·min−1) was adopted hoping to reach optimum conditions for wear resistance and impact toughness. The optimum condition for both properties was recorded at heat input of 16.78 J·mm−2. The present findings reflect that the microhardness values and wear resistance clearly increased after laser hardening by almost three times due to laser surface hardening, whereas, the impact toughness was increased from five joules obtained from conventionally heat-treated samples to 6.4 J as gained from laser-treated samples.

scholarly journals A Study of the Impact of Graphite on the Kinetics of SPS in Nano- and Submicron WC-10%Co Powder Compositions

Ceramics ◽  
2021 ◽  
Vol 4 (2) ◽  
pp. 331-363
Author(s):  
Eugeniy Lantcev ◽  
Aleksey Nokhrin ◽  
Nataliya Malekhonova ◽  
Maksim Boldin ◽  
Vladimir Chuvil'deev ◽  
...  
Keyword(s):  
Activation Energy ◽  
Solid Phase ◽  
Continuous Heating ◽  
Diffusion Creep ◽  
Hard Alloys ◽  
Fine Grained ◽  
Plasma Sintering ◽  
Spark Plasma ◽  
The Impact ◽  
Kinetics Of

This study investigates the impact of carbon on the kinetics of the spark plasma sintering (SPS) of nano- and submicron powders WC-10wt.%Co. Carbon, in the form of graphite, was introduced into powders by mixing. The activation energy of solid-phase sintering was determined for the conditions of isothermal and continuous heating. It has been demonstrated that increasing the carbon content leads to a decrease in the fraction of η-phase particles and a shift of the shrinkage curve towards lower heating temperatures. It has been established that increasing the graphite content in nano- and submicron powders has no significant effect on the SPS activation energy for “mid-range” heating temperatures, QS(I). The value of QS(I) is close to the activation energy of grain-boundary diffusion in cobalt. It has been demonstrated that increasing the content of graphite leads to a significant decrease in the SPS activation energy, QS(II), for “higher-range” heating temperatures due to lower concentration of tungsten atoms in cobalt-based γ-phase. It has been established that the sintering kinetics of fine-grained WC-Co hard alloys is limited by the intensity of diffusion creep of cobalt (Coble creep).

scholarly journals Tempforming as an Advanced Processing Method for Carbon Steels

Metals ◽  
2020 ◽  
Vol 10 (12) ◽  
pp. 1566
Author(s):  
Anastasiya Dolzhenko ◽  
Rustam Kaibyshev ◽  
Andrey Belyakov
Keyword(s):  
Impact Toughness ◽  
Crack Propagation ◽  
Large Strain ◽  
High Strength ◽  
Close Relation ◽  
Carbon Steels ◽  
Processing Method ◽  
Propagation Mode ◽  
Displacement Curve ◽  
The Impact

The microstructural mechanisms providing delamination toughness in high-strength low-alloyed steels are briefly reviewed. Thermo-mechanical processing methods improving both the strength and impact toughness are described, with a close relation to the microstructures and textures developed. The effect of processing conditions on the microstructure evolution in steels with different carbon content is discussed. Particular attention is paid to tempforming treatment, which has been recently introduced as a promising processing method for high-strength low-alloyed steel semi-products with beneficial combination of strength and impact toughness. Tempforming consists of large strain warm rolling following tempering. In contrast to ausforming, the steels subjected to tempforming may exhibit an unusual increase in the impact toughness with a decrease in test temperature below room temperature. This phenomenon is attributed to the notch blunting owing to easy splitting (delamination) crosswise to the principle crack propagation. The relationships between the crack propagation mode, the delamination fracture, and the load-displacement curve are presented and discussed. Further perspectives of tempforming applications and promising research directions are outlined.

Mechanical Properties of Equal-Channel Angular Extrusion-Processed Al-20Zn Alloy

2012 ◽  
Vol 445 ◽  
pp. 195-200
Author(s):  
Murat Aydin ◽  
Yakup Heyal
Keyword(s):  
Mechanical Properties ◽  
Impact Toughness ◽  
Equal Channel Angular Extrusion ◽  
Considerable Change ◽  
Fatigue Properties ◽  
Dendritic Microstructure ◽  
Two Phase ◽  
Angular Extrusion ◽  
Alloy Increase ◽  
The Impact

The mechanical properties mainly tensile properties, impact toughness and high-cycle fatigue properties, of two-phase Al-20Zn alloy subjected to severe plastic deformation (SPD) via equal-channel angular extrusion (ECAE) using route A up to 2 passes were studied. The ECAE almost completely eliminated as-cast dendritic microstructure including casting defects such as micro porosities. A refined microstructure consisting of elongated micro constituents, α and α+η eutectic phases, formed after ECAE via route A. As a result of this microstructural change, mechanical properties mainly the impact toughness and fatigue performance of the as-cast Al-20Zn alloy increased significantly through the ECAE. The rates of increase in fatigue endurance limit are approximately 74 % after one pass and 89 % after two passes while the increase in impact toughness is 122 %. Also the yield and tensile strengths of the alloy increase with ECAE. However, no considerable change occurred in hardness and percentage elongation of the alloy. It was also observed that the ECAE changed the nature of the fatigue fracture characteristics of the as-cast Al-20Zn alloy.

Physical Simulation of Weldability of Weldox 1300 Steel

2013 ◽  
Vol 762 ◽  
pp. 551-555 ◽  
Author(s):  
Marek Stanislaw Węglowski ◽  
Marian Zeman ◽  
Miroslaw Lomozik
Keyword(s):  
Mechanical Properties ◽  
Impact Toughness ◽  
Physical Simulation ◽  
High Strength ◽  
Parent Material ◽  
Cooling Time ◽  
Electron Microscopies ◽  
Transmission Electron ◽  
Transformation Diagrams ◽  
The Impact

In the present study, the investigation of weldability of new ultra-high strength - Weldox 1300 steel has been presented. The thermal simulated samples were used to investigate the effect of welding cooling time t8/5 on the microstructure and mechanical properties of the heat affected zone (HAZ). In the frame of these investigation the microstructure was studied by the light (LM) and transmission electron microscopies (TEM). It has been shown that the microstructure of the Weldox 1300 steel is composed of tempered martensite, and inside the laths the minor precipitations mainly V(CN) and molybdenum carbide Mo2C were observed. Mechanical properties of parent material were analysed by the tensile, impact and hardness tests. In details the influence of cooling time in the range of 2,5 - 300 s. on hardness, impact toughness and microstructure of simulated HAZ was studied by using welding thermal simulation test. The results show that the impact toughness and hardness decrease with the increase of t8/5 under the condition of a single thermal cycle in simulated HAZ. The continuous cooling transformation diagrams (CCT-W for welding conditions) of Weldox 1300 steel for welding purposes was also elaborated. The steel Weldox 1300 for cooling time in the range of 2,5 - 4 s showed martensite microstructure, for time from 4 s to 60 s mixture of martensite and bainite, and for longer cooling time mixture of ferrite, bainite and martensite. The results indicated that the weldability of Weldox 1300 steel is limited and to avoid the cold cracking the preheating procedure or medium net linear heat input should be used.

Effects of oxygen content on microstructure and impact toughness of high heat input flux-cored wire weld metals

2018 ◽  
Vol 115 (4) ◽  
pp. 410
Author(s):  
Fengyu Song ◽  
Yanmei Li ◽  
Ping Wang ◽  
Fuxian Zhu
Keyword(s):  
Grain Size ◽  
Impact Toughness ◽  
Weld Metal ◽  
Oxygen Content ◽  
Heat Input ◽  
High Heat ◽  
Cored Wire ◽  
Weld Metals ◽  
High Heat Input ◽  
The Impact

Three weld metals with different oxygen contents were developed. The influence of oxygen contents on the microstructure and impact toughness of weld metal was investigated through high heat input welding tests. The results showed that a large number of fine inclusions were formed and distributed randomly in the weld metal with oxygen content of 500 ppm under the heat input condition of 341 kJ/cm. Substantial cross interlocked acicular ferritic grains were induced to generate in the vicinity of the inclusions, primarily leading to the high impact toughness at low temperature for the weld metal. With the increase of oxygen content, the number of fine inclusions distributed in the weld metal increased and the grain size of intragranular acicular ferrites decreased, which enhanced the impact toughness of the weld metal. Nevertheless, a further increase of oxygen content would contribute to a great diminution of the austenitic grain size. Following that the fraction of grain boundary and the start temperature of transformation increased, which facilitated the abundant formation of pro-eutectoid ferrites and resulted in a deteriorative impact toughness of the weld metal.

Effect of powder oxidation on the impact toughness of electron beam melting Ti-6Al-4V

2017 ◽  
Vol 17 ◽  
pp. 123-134 ◽  
Author(s):  
W.A. Grell ◽  
E. Solis-Ramos ◽  
E. Clark ◽  
E. Lucon ◽  
E.J. Garboczi ◽  
...  
Keyword(s):  
Electron Beam ◽  
Impact Toughness ◽  
Electron Beam Melting ◽  
The Impact

Effect of β-Al5FeSi and π-Al8Mg3FeSi6 Phases on the Impact Toughness and Fractography of Al–Si–Mg-Based Alloys

2017 ◽  
Vol 12 (1) ◽  
pp. 148-163 ◽  
Author(s):  
E. A. Elsharkawi ◽  
M. H. Abdelaziz ◽  
H. W. Doty ◽  
S. Valtierra ◽  
F. H. Samuel
Keyword(s):  
Impact Toughness ◽  
The Impact
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