Ilare Bordeasu - Academia.edu (original) (raw)

Papers by Ilare Bordeasu

Tribology Letters, Jun 24, 2015

The cavitation erosion of Ti–6Al–4V nitrided by Nd:YAG pulsed laser samples was investigated for ... more The cavitation erosion of Ti–6Al–4V nitrided by Nd:YAG pulsed laser samples was investigated for different pulse durations. Hardness in the range of 1045–900HV0.2, was obtained for pulse duration ranging from 10 to 4 ms, respectively. All the Ti–6Al–4V nitrided samples showed a better cavitation erosion behavior compared to only annealed sample. The best behavior was observed for the sample nitrided with a 4-ms pulse and the weakest one 10-ms pulse. The harder nitride layer showed a brittle behavior during the process, leading to a reduced resistance during the cavitational attack. The more ductile surface of the annealed samples suffered a plastic deformation and the incipient damage generated by the cavitation bubbles lead to plastically deformed surface craters. By contrast, the nitrided samples with high hardness, low ductility and internal stresses increase the cracking sensibility and reduce the resistance to plastic deformation, leading to exfoliations in the brittle areas containing cracks.

Journal of Materials Engineering and Performance, Apr 8, 2016

During processing or use, duplex steels can be subjected to heating at high temperatures that can... more During processing or use, duplex steels can be subjected to heating at high temperatures that can affect their behavior. This work aims to correlate the influence of the sensitization treatment on the ultrasonic cavitation erosion behavior of a UNS S31803 (X2CrNiMoN22-5-3) duplex stainless steel. Duplex stainless steels, formed as a result of rapid cooling after solution annealing, are sensitized at temperatures of 475 and 850 °C, respectively, leading to hardening and embrittlement due to the spinodal decomposition of the ferrite and the precipitation of secondary phases. The ultrasonic cavitation erosion experiments showed that the sensitization at 850 °C reduced the mean depth of erosion by about 11% and the mean depth of erosion rate by 28%. By contrast, the sensitization at 475 °C deteriorates the cavitation erosion resistance, increasing the erosion parameters by up to 22%, compared to the solution annealed state.

Materials Today: Proceedings, 2021

Abstract The results presented in this paper demonstrate the ability of the TIG welding process i... more Abstract The results presented in this paper demonstrate the ability of the TIG welding process in the pulsed current to produce layers with good functional properties for the engineering surfaces. The Stellite-21 alloy was deposited on a duplex stainless steel substrate, X2CrNiMoN22-5–3, in a range of process parameters that allow control of linear energy and cooling rate. The optimum welding conditions led to the formation of a coating free of pores and cracks, with a good adhesion to the substrate. The morphology and performance of the deposited layers were studied by optical microscopy and hardness measurements.

MP MATERIALPRUEFUNG - MP MATERIALS TESTING, Jul 1, 2022

Cobalt-based alloys, called Stellite, have a microstructure consisting of complex carbides disper... more Cobalt-based alloys, called Stellite, have a microstructure consisting of complex carbides dispersed in a Co-based solid solution matrix. These alloys are resistant to corrosion, erosion through cavitation, abrasive, and sliding wear. To increase the erosion resistance through cavitation, hardfacing of the stainless steel duplex X2CrNiMoN22-5-3 with Stellite 21 alloy was performed using the pulsed tungsten inert gas (TIG) process. The positive effects of the hardfacing process are the low heat input, reduced distortions, controlled volume of the weld, and reduced susceptibility to hot cracking. The effect of dilution is essential for the quality of the deposited layers and, in this sense, the TIG pulsed current welding process was performed to reduce the excess linear energy and implicitly the substrate melting. Iron dilution levels were in the range between 5.9 and 6.1. The higher Fe content in the first layer does not significantly reduce its hardness or wear resistance through erosion cavitation. Compared with the substrate material, the cavity erosion resistance increases 7 to 11 times even in the first layer hardened by the TIG pulsed current welding process.

International Journal of Materials Research, Apr 14, 2015

Ultrasonic cavitation experiments using a piezoceramic-based apparatus, according to ASTM G32-201... more Ultrasonic cavitation experiments using a piezoceramic-based apparatus, according to ASTM G32-2010, were performed on heat and thermochemically treated Cr – Mn low alloyed steel samples. The microstructure in annealed, carburized and tempered states as well as following a duplex treatment (carburized, surface induction hardening and tempering) was analyzed before and after the cavitation erosion tests. The results show the advantage of the duplex treatment, with a significant increase of up to 20 times of the cavitation erosion resistance compared to the annealed state and reveal that the main mechanism for surface deterioration is micro-cracking. The observations are important for the improvement of the behaviour for parts used in hydraulic equipment, for which the volume hardening following the carburization can be replaced by cost-efficient surface induction hardening treatments.

Journal of physics, Jul 1, 2023

Aluminium-based alloy type 7075 is known for its good ductility, high mechanical strength, toughn... more Aluminium-based alloy type 7075 is known for its good ductility, high mechanical strength, toughness and high fatigue strength, which is why it is mainly used in the construction of dynamically stressed parts in the structure of airplanes, vehicles and ships. Although it has these qualities, at present its behavior has not been studied at the hydrodynamic stresses that allow it to be used in parts that work in cavitation conditions, such as pump rotors and boat propeller blades. Therefore, the research in this paper highlights the behavior of laminated semi-finished structures and obtained by heat treatment of artificial aging at 180°C, with a maintenance time of one hour. Of the 7075 alloy at the demands generated by the vibrating cavity, created by the standard vibrating device with piezoceramic crystals (frequency of 20 kHz, amplitude of 50 µm and electrical power of 500 W). Analysis based on the curves MDE (t) and MDER (t), of the specific parameters of cavitation erosion MDEmax and MDERs as well as of the macro and microscopic images of the eroded structures of cavitation show that, compared to the delivered state (semi-finished), by the heat treatment applied the microstructure does not change cavitation

Revista De Chimie, Jan 15, 2018

IOP conference series, Oct 26, 2018

Advanced Materials Research, Jul 1, 2015

Duplex stainless steels are processed by a process of hot or cold plastic deformation and welding... more Duplex stainless steels are processed by a process of hot or cold plastic deformation and welding operations. Their properties of the use depend on the type of product (deformed, welded) and to the final heat treatment. The proportion of the basic structural constituents (austenite and ferrite) essentially depends on the chemical composition and cooling rate from high temperatures. This paper shows the that slow cooling in the furnace at the high temperature (1060 ° C) lead to a predominantly austenitic microstructure (cca.75%) while that cooling in the water sudden limited the transformation austenite → ferrite, so that the microstructure will be composed of cca.52% F + 48% A.These modifications by structure justify the changes the occurring with respec ultrasonic erosion cavitation behavior.

Applied Mechanics and Materials, Oct 1, 2015

One of the most harmful effects of cavitation, with strong influence on the life of the hydraulic... more One of the most harmful effects of cavitation, with strong influence on the life of the hydraulic machines is the destruction caused by erosion Since its discovery, over 150 years ago, evaluating the degradation is achieved by mass of material removed by erosion in a given time, which in the case of rotors and blades of hydraulic machines and marine propeller blades are equivalent by amount of electrode consumption for filling the voids left by the removal of material. Laboratory research on cavitation, from the beginning until now, evaluates the intensity of cavitation erosion rate, defined as a mass of material removed by erosion at a certain time of attack.The purpose of this paper is to develop and validate a technique based on vibroacoustic signal analysis of corroded samples, and that through their natural frequencies deviations to emphasize mass loss.The experimental measurement of the vibroacustic response of corroded specimens is carried out by using a condenser microphone. The vibration responses, in free-free conditions of the specimens, are analyzed using algorithm based on Fast Fourier Transform (FFT). The results are compared with other indicators of cavitation corrosion, such as lost mass and mass loss rate.

Metallurgical and Materials Transactions, May 30, 2019

Advanced Materials Research

Among other parts made of brass there are also the blades and the rotors of the hydraulic machine... more Among other parts made of brass there are also the blades and the rotors of the hydraulic machines, respectively ship propellers, which during operation are degraded by cavitation erosion. As a result, most of the researches, including the most recent ones, are focused on the morphological analysis of structures eroded under the impact of micro-jets and shock waves, produced by cavitation hydrodynamics. The goal is to create new materials, but also to use new treatment technologies to increase cavitation resistance. As the literature is quite poor in studies related to the materials resistance to cavitation erosion, respectively treatments and technological procedures of it’s improvement, this paper presents the research results on the behavior of vibration cavitation erosion, carried out on three sets of CuZn39Pb3 brass samples, subjected to volumetric heat treatments of hardening for putting in solution at 800°C, followed by tempering at 250°C, 400°C and 600°C. The characterizatio...

METAL 2021 Conference Proeedings, 2021

Key Engineering Materials, 2021

The paper presents the results of the behavior and resistance to the erosion by vibrating cavitat... more The paper presents the results of the behavior and resistance to the erosion by vibrating cavitation of the CuZn39Pb3 brass, obtained by quenching the volume heat treatment from 800°C with water cooling, followed by the stress-relief to 250°C, with air cooling. Comparison with both the delivery status and the naval brass (used for ship propellers), based on the characteristic parameters values, recommended by the ASTM G32 standards and used in the Cavitation Laboratory of the Polytechnic University of Timisoara, shows that the hardness increase resulted from the heat treatment led to a significant increase of resistance to vibrating cavitation.

METAL 2019 Conference Proeedings, 2019

Journal of Physics: Conference Series, 2020

Among the materials, often used in manufacturing details subjected to cavitation erosion, such as... more Among the materials, often used in manufacturing details subjected to cavitation erosion, such as pump impellers, propellers, fittings, valves body, etc. there are also CuZnPb brasses. Their use in molded or laminated condition, for pieces subjected to cavitation, is of short duration due to degradation through the erosion. For this reason, any method of increasing the extension of life, is beneficial. In this direction are enrolled also the results obtained in this paper, obtained by the cavitation tests made on CuZn39Pb3 brass, subjected to three the volumetric heat treatment regimes. Appreciation of cavitation resistance, of each treatment regime, is based on the evolution of average durability δ ¯ c a v defined by K.Steller. The research program, conducted on the standard vibration device with piezo ceramic crystals, in the Cavitation Laboratory of the Polytechnic University of Timisoara, shows that the best results are offered by hardening treatment.