scholarly journals Cavitation erosion damage of self-fluxing NiCrSiB hardfacings deposited by oxy-acetylene powder welding

2021 ◽  
Vol 2130 (1) ◽  
pp. 012033
Author(s):  
M Szala
Keyword(s):  
Cavitation Erosion ◽  
Physical And Mechanical Properties ◽  
Optical Microscope ◽  
General Idea ◽  
Testing Time ◽  
Damage Estimation ◽  
Material Microstructure ◽  
Material Loss ◽  
Erosion Damage ◽  
Multiphase Materials

Abstract This paper comparatively investigates the cavitation erosion damage of two self-fluxing NiCrSiB hardfacings deposited via the oxy-acetylene powder welding method. Examinations were conducted according to the procedure given by ASTM G32 standard. In order to research cavitation erosion (CE), the vibratory apparatus was employed. The cavitation damaged surfaces were inspected using a scanning electron microscope, optical microscope and surface profilometer. The hardness of the A-NiCrSiB hardfacing equals 908HV while that of C-NiCrSiB amounts to 399HV. The research showed that the CE resistance of C-NiCrSiB is higher than that of A-NiCrSiB. The results demonstrate that in the case of multiphase materials, like the NiCrSiB hardfacings, hardness cannot be the key factor for cavitation erosion damage estimation whereas it is strongly subjected to material microstructure. In order to qualitatively recognise the cavitation erosion damage of the NiCrSiB self-fluxing hardfacings at a given exposure time, the following factors should be respected: physical and mechanical properties, material microstructure and also material loss and eroded surface morphology, both stated at specific testing time. The general idea for the cavitation erosion damage estimation of the NiCrSiB oxy-acetylene welds was presented.

scholarly journals Vibrational Stresses of Damaged Steam Turbine Blades After Renovation Repair

2021 ◽  
Vol 24 (1) ◽  
pp. 42-52
Author(s):  
Mykola H. Shulzhenko ◽  
◽  
Anton S. Olkhovskyi ◽  
Keyword(s):  
Mechanical Properties ◽  
Strain State ◽  
Turbine Blades ◽  
Excitation Frequency ◽  
Physical And Mechanical Properties ◽  
Erosion Damage ◽  
Trailing Edges ◽  
Blade System ◽  
Last Stage ◽  
Maximum Stresses

The last-stage blades of K-1000-60/3000 steam turbines operate in a humid steam environment, which causes erosion damage in the blades and reduction in their residual life. The relevance of this work is related to the need to continue the safe operation of such turbine blades. A number of variants of the finite-element models of individual blades and last-stage blades in the disk-blade systems of the above turbines are considered. Results of the numerical study of the influence of blade part removals in erosion damage zones after renovation repair on the vibration characteristics of individual blades and blades in the disk-blade system are presented. An analysis of the stress-strain state under the conditional load from the steam flow during the forced oscillations of individual blades and blades in the disk-blade system is carried out. The loads are given as evenly distributed and linearly variable on blade surfaces. The dependence of the maximum equivalent vibration stresses on excitation frequency is determined. It is assumed that the physical and mechanical properties of the blade material are preserved (as for the original version) after the renovation repair of blades and processing of their surfaces. There is a significantly greater reduction in the vibration stresses of blades in the disk-blade system than in the stresses of individual blades. Graphs of the dependence of the maximum stresses on excitation frequency both for undamaged individual blades and blades in the disk-blade system after their renovation repair are given. Various variants of blade part removals in areas of blade leading and trailing edges are considered. It is shown that with decreasing chords of blades after renovation repair, frequency regions of increased vibration may appear in lower blade parts. In the lower parts of individual blades and blades in the disk-blade system, the maximum stresses increase in comparison with their values in undamaged blades. With the change in the stress-strain state of rotor blades in comparison with the original version of undamaged blades, the possibility of extending their safe lifetime in case of multi-cycle fatigue is assessed. The safe lifetime of the considered blades with a chord of at least 150 mm after their renovation repair can be extended according to their stresses, if the cyclic symmetry of the disk-blade system is not violated, and the physical and mechanical properties of the material are preserved after the processing of damage removal zones on blade trailing edges.

Investigation Into Cavitation Erosion Pits

2009 ◽  
Vol 131 (3) ◽  
Author(s):  
A. Abouel-Kasem ◽  
A. Ezz El-Deen ◽  
K. M. Emara ◽  
S. M. Ahmed
Keyword(s):  
Stainless Steel ◽  
Cavitation Erosion ◽  
Pure Aluminum ◽  
The Other ◽  
304 Stainless Steel ◽  
Testing Time ◽  
Limited Effect ◽  
Fatigue Process

Cavitation erosion pits and their effects on erosion progression were investigated in detail for SUS 304 stainless steel, α+β brass (60/40), and pure aluminum (Al-99.999 and Al-99.92) by means of vibratory erosion. Two kinds of erosion pits were found on the specimen surfaces, one by microjet impact and the other by shockwave blow. Systematic observations of the feature of microjet-pits with the testing time showed that the sizes and shapes of microjet-pits did not change at all and such pits scarcely played an important role in developing the erosion. Moreover, the feature morphology of eroded surfaces, and dislodged particles and their large sizes revealed that microjet-pits had a limited effect on erosion and that the predominant failure was a fatigue process.

Production of cavitation erosion damage by means of an electromagnetic shock wave source.

2009 ◽  
Vol 125 (4) ◽  
pp. 2561-2561
Author(s):  
Qi Wang ◽  
Nicholas J. Manzi ◽  
R. Glynn Holt ◽  
Ronald A. Roy ◽  
Robin O. Cleveland
Keyword(s):  
Shock Wave ◽  
Cavitation Erosion ◽  
Wave Source ◽  
Erosion Damage ◽  
Electromagnetic Shock ◽  
Electromagnetic Shock Wave

Development of Epoxy Grout Containing Fine Waste from Production of Mineral Wool Board Insulation

2018 ◽  
Vol 878 ◽  
pp. 275-280 ◽  
Author(s):  
Jakub Hodul ◽  
Tomáš Žlebek ◽  
Rostislav Drochytka
Keyword(s):  
Thermal Resistance ◽  
Epoxy Resin ◽  
Filler Content ◽  
Physical And Mechanical Properties ◽  
Optical Microscope ◽  
Mechanical Analysis ◽  
Mineral Wool ◽  
Raw Material ◽  
Strength Increase ◽  
Economic Point

Within this work, it was experimentally verified that the waste from mineral wool board insulation production (WIRG) with high portion of glass recyclate (> 80%) and no organic material seems like ideal filler for polymer grouting materials. The main objective was to develop a progressive grout on epoxy basis with as high content of this secondary raw material as possible, while achieving physical and mechanical properties as e.g. very fast strength increase and high thermal resistance. With regard to the consistency of epoxy grout in the fresh state, three different filling were tested, namely 60%, 65% and 70%. The grout with lower filling is too fluid, and it is also disadvantageous from an economic point of view because a large amount of epoxy resin is used. On the other hand, at higher filing, it is not possible to mix the filler into epoxy resin properly. Setting of an optimal filler content in the mixture was performed mostly on the basis of the results of compressive and three-point flexural strength test. It was found out that the optimal amount of the filler is 65%. In case of the best formulation with optimal filler content (65% WIRG), the thermal resistance was monitored by determination of the glass transition temperature (Tg) by the dynamic mechanical analysis (DMA) method. Furthermore, the optical microscope with high resolution was used to monitor filler distribution and homogeneity of the hardened developed epoxy grout.

An Experimental Study on Effect of T-Joint’s Root Gap on Welding Properties

2017 ◽  
Vol 863 ◽  
pp. 323-327 ◽  
Author(s):  
Yustiasih Purwaningrum ◽  
Panji Lukman Tirta Kusuma ◽  
Dwi Darmawan
Keyword(s):  
Mechanical Properties ◽  
Base Metal ◽  
Testing Machine ◽  
Low Carbon Steel ◽  
Physical And Mechanical Properties ◽  
Optical Microscope ◽  
Low Carbon ◽  
Weld Metals ◽  
A Value ◽  
Welding Properties

The aimed of this research is to investigate the effect of T-Joint’s root gap on physical and mechanical properties of weld metal. Low carbon steel were joined in T-joint types using MIG (Metal Inert Gas) with variation of root gap. The root gap used were 0 mm, 3 mm and 6 mm. The physical properties examined with chemical composition, microstructure and corrosion using optical microscope. The mechanical properties were measured with respect to the strength and hardness using Universal testing machine and Vickers Microhardness. The results show that the highest value found in welds with a gap of 3 mm with a value of 163.57 MPa. Hardness value is directly proportional to the tensile strength of the material. The highest value found in welds with root gap of 3 mm, followed by root gap of 6 mm, and 0 mm Hardness values in the welding area is higher than the parent metal and HAZ because the number of Si, Mn and Cu elements in the welding metals are bigger than base metal. Weld with all variation of root gap have a good corrosion resistance because the corrosion rate in welds with various root gap have a value below 0.02 mmpy. Microstructure of weld metals were Accicular ferrite, Widmanstatten ferrite, and grain boundary ferrite, while microstructure of base metal and HAZ were ferrite and perlite.

Damaging effect of salt crystallization on highly porous limestone from Hungary

2020 ◽  
Author(s):  
Nikoletta Rozgonyi-Boissinot ◽  
Mohammad Ali Khodabandeh
Keyword(s):  
Tensile Strength ◽  
Sea Water ◽  
Water Saturation ◽  
Salt Content ◽  
Physical And Mechanical Properties ◽  
Optical Microscope ◽  
Sodium Sulphate ◽  
Capital City ◽  
Salt Crystallization ◽  
Petrophysical Properties

<p>One of the most important weathering processes on stone-built monuments is the crystallization of salts. Since the transport material of these substances is water, the porous rock types are particularly affected. In Hungary many monuments and historic buildings have been constructed from oolithic Miocene limestone. So in this study, the effect of salt crystallization on the physical and mechanical properties of high porous limestone has been investigated. Samples were obtained from Sóskút (near to Budapest, the capital city of Hungary).</p><p>At first the petrophysical properties of the stone were determined. The porosity of the investigated stone type was 26-34 V/V%, the uniaxial compressive strength (4-5 MPa) and the Brazilian tensile strength (0,4-0,5 MPa) were very low. A special proper of this rock type is the large-pore system (2-3mm) between the ooid fragments.</p><p>Sodium chloride (NaCl) and sodium sulphate (Na<sub>2</sub>SO<sub>4</sub>) were used to investigate the effect of salt crystallization. Cylindrical rock samples were exposed to salt solutions of 14 m/m% Na<sub>2</sub>SO<sub>4</sub> (MSZ EN 12370) and 5% NaCl solution (sea water salt content). After 15 salted water saturation- drying cycles the changes of mineralogical and petrophysical properties and indirect tensile strength of the samples were investigated. The damages on the pore walls were determined with scanning electron microscope (SEM) and the building of scaling layers on the stone surfaces were investigated with optical microscope.</p>

Modeling the Material Microstructure Effects on the Surface Generation Process in Microendmilling of Dual-Phase Materials

2012 ◽  
Vol 134 (4) ◽  
Author(s):  
A. M. Abdelrahman Elkaseer ◽  
S. S. Dimov ◽  
K. B. Popov ◽  
M. Negm ◽  
R. Minev
Keyword(s):  
Chip Thickness ◽  
Machining Process ◽  
Surface Generation ◽  
Dual Phase ◽  
Generation Process ◽  
Phase Boundaries ◽  
Material Microstructure ◽  
Workpiece Material ◽  
Multiphase Materials ◽  
Proposed Model

The anisotropic behavior of the material microstructure when processing multiphase materials at microscale becomes an important factor that has to be considered throughout the machining process. This is especially the case when chip-loads and machined features are comparable in size to the cutting edge radius of the tool, and also similar in scale to the grain sizes of the phases present within the material microstructure. Therefore, there is a real need for reliable models, which can be used to simulate the surface generation process during microendmilling of multiphase materials.This paper presents a model to simulate the surface generation process during microendmilling of multiphase materials. The proposed model considers the effects of the following factors: the geometry of the cutting tool, the feed rate, and the workpiece material microstructure. Especially, variations of the minimum chip thickness at phase boundaries are considered by feeding maps of the material microstructure into the model. Thus, the model takes into account these variations that alter the machining mechanism from a proper cutting to ploughing and vice versa, and are the main cause of microburr formation. By applying the proposed model, it is possible to estimate more accurately the resulting roughness because the microburr formation dominates the surface generation process during microendmilling of multiphase materials. The proposed model was experimentally validated by machining two different samples of dual-phase steel under a range of chip-loads. The roughness of the resulting surfaces was measured and compared to the predictions of the proposed model under the same cutting conditions. The results show that the proposed model accurately predicts the roughness of the machined surfaces by taking into account the effects of material multiphase microstructure. Also, the developed model successfully elucidates the mechanism of microburr formation at the phase boundaries, and quantitatively describes its contributions to the resulting surface roughness after microendmilling.

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