Metallurgical and tribological aspects for squat formation in the aluminothermic weld HAZ edges of rails welded using aluminothermy

2020 ◽  
Vol 72 (9) ◽  
pp. 1123-1131
Author(s):  
Luiz Henrique Dias Alves ◽  
Tiago Carvalho Tepedino ◽  
Mohammad Masoumi ◽  
Gustavo Tressia ◽  
Helio Goldenstein
Keyword(s):  
Weld Metal ◽  
Peer Review ◽  
Microstructural Characterization ◽  
Tensile Tests ◽  
Hardness Profile ◽  
Content Type ◽  
Heavy Haul ◽  
Pin On Disk ◽  
Tribological Characterization

Purpose The purpose of this paper is to present the results of a metallurgical, mechanical and tribological characterization of the weld and heat-affected zone (HAZ) of aluminothermic welding of premium rails used in heavy haul, looking into the origins of the squat defects associated with rail wear. Design/methodology/approach A full factorial design of experiment was carried out for 24 welds of premium and super premium rails. The factors studied were chemical composition, welding gap and preheating time. The welds were inspected visually and by ultrasound to detect superficial and internal defects and characterized by macrographic analysis, hardness profile, tensile tests and microstructural characterization in scanning electronic microscopy. Pin-on-disk test were carried out to compare the tribological behavior of the different regions of the weld rail. Findings Squat formation was shown to be associated with spheroidized pearlite regions formed on the HAZ of the welds, presenting near half the hardness of the weld metal. Thermal analysis showed that spheroidized pearlite is a result of partial austenitization at these positions. Tribological tests showed that low hardness regions presented smaller wear resistance than both the weld metal and the parent rail. Tensile test of the whole region resulted in brittle fracture along the weld metal. Originality/value The results showed that it is essential to reduce the dimensions of the HAZ and the width of the hardness drop area to mitigate squat formation in the HAZ edges. Peer review The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-01-2020-0020/

Comparison of tribological performances of sulfur based and boron succuminide containing antiwear additive with ZDDP by engine bench tests

2016 ◽  
Vol 68 (4) ◽  
pp. 482-496 ◽  
Author(s):  
Doğuş Özkan ◽  
M. Barış Yağci ◽  
Özgür Birer ◽  
Hakan Kaleli
Keyword(s):  
Antiwear Additive ◽  
Lubricating Oil ◽  
Free Products ◽  
Environment Friendly ◽  
Content Type ◽  
Bench Tests ◽  
Lubrication Oil ◽  
Lubrication Oils ◽  
Tribological Characterization

Purpose This study aims to evaluate and compare by 100 hours engine bench tests the tribological performances of two types of lubrication oils, which were sulfur-based, boron succinimide-containing antiwear package (NP-3) oil and conventional zinc dialkyldithiophosphate (ZDDP)-containing (R-1) oil. Design/methodology/approach The tribological performances of the oils were evaluated in three main contexts, including engine tests, physical/chemical changes and surface analysis. Findings Results showed that NP-3 lubrication oil, which was environment- and catalyst-friendly, can be an alternative lubrication oil with its tribological performance due to similar antiwear characteristics with the ZDDP. Originality/value Attempts to develop catalysis- and environment-friendly antiwear additive packages have not presented popular or commonly used ZDDP-free products for the vehicle industry. This study presents tribological characterization of a newly developed ZDDP-free lubricating oil by engine bench tests.

Deformation mechanism and tribological behavior of hydrogen-free carburized layer on Ti-6Al-4V alloy

2020 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Tian Tian ◽  
Ruibo Zhao ◽  
Dongbo Wei ◽  
Kai Yang ◽  
Pingze Zhang
Keyword(s):  
Peer Review ◽  
Deformation Mechanism ◽  
Tribological Behavior ◽  
Scratch Test ◽  
Hardness Profile ◽  
Cross Sectional ◽  
Content Type ◽  
Elastic Plastic ◽  
The Coefficient Of Friction ◽  
Carburized Layer

Purpose The purpose of this paper is to expound the relationship among microstructure, mechanical property, tribological behavior and deformation mechanism of carburized layer deposited on Ti-6Al-4V alloy by double-glow plasma hydrogen-free carburizing surface technology. Design/methodology/approach Morphologies and phase compositions of the carburized layer were observed by scanning electron microscope and X-ray diffraction. The micro-hardness tests were used to evaluate the surface and cross-sectional hardness of carburized layer. The reciprocating friction and wear experiments under various load conditions were implemented to investigate the tribological behavior of carburized layer. Moreover, scratch test with ramped loading pattern was carried out to illuminate the deformation mechanism of carburized layer. Findings Compared to substrate, the hardness of surface improved to ∼1,100 HV0.1, while the hardness profile of carburized layer presented gradual decrease from ∼1,100 to ∼300 HV0.1 within the distance of the total carburizing-affected region about 30 µm. The coefficient of friction, wear rate and wear morphology of carburized layer were analyzed. Scratch test indicated that the deformation process of carburized layer could be classified into three mechanisms (elastic, changing elastic–plastic and stable elastic–plastic mechanisms), and the deformation transition of the carburizing-affected region was from changing elastic–plastic to elastic mechanisms. Both the elastic and changing elastic–plastic mechanisms are conducive to the wearing course. Originality/value Using this technology, hydrogen embrittlement was avoided and wear resistance property of titanium alloy was greatly improved. Simultaneously, the constitutive relation during the whole loading process was deduced in terms of scratch approach, and the deformation mechanism of carburized layer was discussed from a novel viewpoint. Peer review The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-11-2019-0489/

Microstructural Characterization of Dual and Multiphase Steels Applied to Automotive Industry

2014 ◽  
Vol 775-776 ◽  
pp. 146-150 ◽  
Author(s):  
Cristina Sayuri Fukugauchi ◽  
Antonio dos Reis Faria Neto ◽  
Rosinei Batista Ribeiro ◽  
Marcelo dos Santos Pereira
Keyword(s):  
Mechanical Properties ◽  
Microstructural Characterization ◽  
Tensile Tests ◽  
Ferrite Matrix ◽  
Microstructure Characterization ◽  
Second Phase ◽  
Dual Phase ◽  
Dual Phase Steels ◽  
Trip Steels

TRIP (Transformation Induced Plasticity) and DP (Dual-Phase) steels are written in a new series of steels which present excellent mechanical properties. As for microstructure aspect, TRIP steels consist on a ferrite matrix with a second phase dispersion of other constituents, such as bainite, martensite and retained austenite, while dual-phase steels consist on martensite dispersion in a ferrite matrix. In order to identify the different microconstituents present in these materials, microstructure characterization techniques by optical microscopy (using different etchants: LePera, Heat-Tinting and Nital) and scanning electron microscopy were carried out. This being so, microstructures were correlated with mechanical properties of materials, determined by means of tensile tests. It is concluded that steels assisted by TRIP effect have a strength and elongation relation higher than the dual-phase one. With microstructure characterization, it was observed phases present in these materials microstructure.

Failure Analysis of a Damaged Helicopter Rescue Hoist Cable

2012 ◽  
Vol 730-732 ◽  
pp. 325-330
Author(s):  
Teresa L.M. Morgado ◽  
Armando Sousa Brito ◽  
Carlos M. Branco
Keyword(s):  
Steel Wire ◽  
Microstructural Characterization ◽  
Tensile Tests ◽  
Work Conditions ◽  
Fractographic Analysis ◽  
Ductile Mode ◽  
Cause Of Failure ◽  
Rescue Hoist

This paper presents the results and main conclusions of a study made to analyze the cause of failure occurred with an austenitic 304 class stainless steel wire rope of a helicopter rescue hoist. The cable is made up of 19 strands, 12 outside and 7 inside. As each strand contains 7 wires, the whole cable is made up of 133 wires. The study includes the chemical and microstructural characterization of the material, as well as the determination of its hardness, mechanical properties and the fractographic analysis by scanning electron microscopy (SEM). Tensile tests were performed for three velocities simulating different work conditions: 250mm/min, 50mm/min and 5mm/min. The fractographic analysis shows that the cable suffered lateral loss of material due to friction and leading to the failure of the remaining material by ductile mode.

High Cycle Fatigue Behavior and Microstructural Characterization of 6013-T4 Aluminum Alloy Laser Welded Joints

2014 ◽  
Vol 891-892 ◽  
pp. 1767-1772
Author(s):  
Rafael Humberto Mota de Siqueira ◽  
Aline C. de Oliveira ◽  
Rudimar Riva ◽  
Antonio Jorge Abdalla ◽  
Carlos Antonio Reis Pereira Baptista ◽  
...  
Keyword(s):  
Thermal Treatment ◽  
Fatigue Behavior ◽  
Laser Beam Welding ◽  
Average Power ◽  
Microstructural Characterization ◽  
Tensile Tests ◽  
Fatigue Properties ◽  
Riveting Process ◽  
Number Of Cycles

Laser beam welding (LBW) may be used in the place of the traditional riveting process for the welding of the stringers to the skin in aircrafts. This work intends to investigate the mechanical behavior of laser welded aluminum AA6013, subjected to post-welding heating treatments (PWHT). A fiber laser with an average power of 1.5 kW was used to weld two 1.6mm thick sheets in T-joint configuration. After welding, the samples were separated in three groups: the first just welded, the second subjected to a PWHT during 4 hours at 190°C and the third during 2 hours at 205°C. Hoop tensile tests showed that the thermal treatment at 190 oC for four hours increased the tensile strength in 76 MPa, but the strain had decreased 4%; the thermal treatment at 205 oC for two hours increased maximum strength in 65MPa, with a decrease in strain of 5%. In T-pull tensile tests, the tensile properties of as-welded and PWHT samples remained the same. Standard S-N curve showed that the welding reduce the number of cycles to failure for the tested stairs. PWHT did not affect fatigue properties.

scholarly journals Mechanical Properties and Microstructural Characterization of Aged Nickel-based Alloy 625 Weld Metal

2018 ◽  
Vol 49 (5) ◽  
pp. 1653-1673 ◽  
Author(s):  
Cleiton Carvalho Silva ◽  
Victor Hugo C. de Albuquerque ◽  
Emerson Mendonça Miná ◽  
Elineudo P. Moura ◽  
João Manuel R. S. Tavares
Keyword(s):  
Mechanical Properties ◽  
Weld Metal ◽  
Microstructural Characterization ◽  
Alloy 625 ◽  
Nickel Based Alloy

Evaluation and Development of Electrodes for Wet Welding of Structural Ship Steels

2010 ◽  
Author(s):  
Valter R. Santos ◽  
Mauri´cio J. Monteiro ◽  
Fernando C. R. Assunc¸a¯o ◽  
Alexandre Q. Bracarense ◽  
Ezequiel C. P. Pessoa ◽  
...  
Keyword(s):  
Weld Metal ◽  
Water Depth ◽  
Microstructural Characterization ◽  
Tensile Tests ◽  
Limiting Factor ◽  
Diffusible Hydrogen ◽  
Class A ◽  
Structural Parts ◽  
In Situ Repair

To better understand the behavior of some commercial wet welding electrodes down to 20 m equivalent water depth as well as to develop a new electrode, a research program was initiated in 2007. This depth is considered the maximum expected in the in situ repair of structural parts of floating production units. The weld metal evaluation was done by microstructural characterization, Vickers hardness, Charpy and tensile tests, chemical analysis, and diffusible hydrogen measurement. The influences of pressure on the mechanical properties of the weld metal are presented and discussed on the basis of chemical composition, microstructure and porosity. The electrode under development showed promising results concerning the possibility to broaden the range of qualified welding procedures. This expectation is based on the good results of diffusible hydrogen, porosity, impact toughness and ductility down to 20 m equivalent water depth. The susceptibility of hydrogen cracking in weld metal and in heat affected zone was estimated comparatively. The presence of hydrogen cracks is discussed as an important limiting factor for the qualification of welding procedures in the class A of the AWS D3.6M:1999 specification.

Corrosion and wear analysis of HVOLF sprayed WC-10CO-4Cr coating on geothermal turbine blade

2019 ◽  
Vol 16 (6) ◽  
pp. 768-774
Author(s):  
Manoj Kumar ◽  
Rohit Upadhyaya
Keyword(s):  
Microstructural Characterization ◽  
X Ray Diffraction ◽  
Spectroscopy Analysis ◽  
Content Type ◽  
Simulated Environments ◽  
Wear And Corrosion ◽  
High Microhardness ◽  
Turbine Steel ◽  
Dip Test

Purpose The purpose of this paper is to develop the high pressure high-velocity oxy-liquid fuel sprayed WC-10Co-4Cr coatings on geothermal turbine 9Cr-1Mo steel for protection against wear and corrosion. Design/methodology/approach The microstructural characterization of as-deposited and corroded coating was done and presented using X-ray diffraction and scanning electron microscope/energy dispersive spectroscopy analysis. Findings The developed coating offered 50 per cent enhanced microhardness (1,200 HV) and 100 per cent enhanced wear resistance, in comparison to bare geothermal turbine steel, respectively. The coating has shown enhanced life in the simulated working conditions (fog test and dip test). This may be because of the high microhardness of the developed coating as per the proven tribological theories. Originality/value Coating offered excellent corrosion resistance in the harsher simulated environments to geothermal turbines.

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