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Low-wetting low-hydrophilicity polipropylene fiber has been treated by means of non-thermal dielectric barrier discharge plasma. The fiber has been characterized before and after the treatment by scanning electron microscopy (SEM), X-ray diffraction, atomic force microscopy (AFM) and industrial tests of submersion in water. The cold plasma was generated in a helium–air mixture at a 2 kHz frequency and 12–18 kV potential. The treatment periods ranged from 1 min up to 3 min. The results present an increase in the oxygen content which rose from 2.5% to 4.8%. SEM analysis reveals a surface change of the fiber with the formation of nodules, which is confirmed by AFM. Water submersion experiments show an enhancement of the hydrophilic capability of the samples.

Several theoretical and experimental studies have been carried out in recent years aimed at enhancing the mechanical resistance and osseo-integration of titanium based dental implants. The often inadequate mechanical properties of commercially pure titanium (CpTi) can lead to the clinical failure of dental materials. A plasma immersion ion implantation (PIII) process has been applied to CpTi samples in an optimized nitrogen/oxygen gas mixture at middle and high temperatures, improving considerably the properties of these. Studies of microhardness, corrosion, AFM, XRD and Raman spectroscopy have been applied in order to evaluate the treated samples whereby highly biocompatible TiO 2 (Rutile) and TiN x layers have been identified. A high corrosion tolerance was found for CpTi, indicating a typical passive behavior of titanium, which can be attributed to a highly stable film formed on the samples placed in Hank's solution. The hardness was improved nearly five times with respect to that of the control material.

Background and Aims The efficacy of a direct application of plasma needle to in vivo wound healing was experimentally studied in mice. This kind of plasma has achieved considerable success in blood coagulation and tissue restoration in mice. In the development of the present study, an argon plasma needle was chosen for coagulation purposes, whereas for healing purposes, a helium plasma needle was used. Methods Treatment was applied with a plasma needle produced by argon and helium to a wound induced in laboratory mice. Tissue regeneration was carried out by three argon plasma treatments with 0.5 SLPM flow for 1 min and three treatments of helium with 1.5 SLPM flow. Intervals between each treatment were 5 min and 60 min for argon and helium plasmas, respectively, thus completing a total treatment time of 180 min. Histological sections were performed to corroborate the internal bleeding and tissue regeneration. Results After three treatments with argon plasma, the blood produced in the wound was coagulated and protein material appeared. By means of treatment with helium plasma, an approach of the wound edges was produced until the conclusion thereof. These results were corroborated histologically. Conclusions This type of acceleration during the skin wound healing process can be attributed to the formation of reactive species such as NO, which were increased in the helium plasma needle with respect to the argon plasma needle.

This paper presents an experimental study of the inactivation in water of two representative classes of bacteria, Gram-negative Escherichia coli and Gram-positive Bacillus subtilis, using pulsed dielectric barrier discharges (PDBDs) in a coaxial arrangement. To this purpose, an adjustable plasma source supplies 25-kV/500-Hz pulses, 30 μs long, at atmospheric pressure, with total energy consumption estimated at about 100 mJ/pulse. The inactivation effect of a PDBD on these types of microorganisms has been previously studied in dependence on an oxygen gas flow mode (null, continuous, and modulate). The results have shown a significant bacterial reduction rate from 108 to 103 cells/mL with E. coli and from 107 to 103 cells/mL with B. subtilis. The inactivation effectiveness is substantially similar in both kinds of bacteria, although some data suggest a greater susceptibility of the Gram-negative E. coli to plasma exposure. Plasma diagnostics was carried out using optical emission spectroscopy whereby the OH radical and reactive oxygen species formation rates in solution were found and the level of ozone produced by the discharge was monitored. Finally, a kinetics model was developed to characterize the chemical species taking place in nonthermal plasma inactivation processes in water.

Using as target a CpTi disk in an atmosphere of argon/oxygen and by rf plasma. First titanium dioxide (TiO 2 ) films were obtained on silicon substrates, and subsequently, these films were doped with nitrogen (N-TiO 2 ). In both processes, along four hours at 390°C of temperature. X-Ray diffraction and Raman spectroscopy confirmed the presence of the nanostructured anatase phase. X-ray photoelectron spectroscopy analyzes indicate that the nitrogen atoms were incorporated into the TiO 2 film with ~33.9 at%. The films reach a thickness of 1.25 μm and 40 nm the average uniformity determined by using an atomic force microscope. Finally, UV-Vis diffuse reflectance spectroscopy outcome evaluated ones an energy band gap reduction from 3.17 eV to 2.95 eV corresponding to TiO 2 films and N-TiO 2 films respectively.

Monitoring basic plasma parameters such as temperature (T), density (n), floating potential (V f ) or Debye length (λ d ) provides vital knowledge during the ion implantation processing of materials immersed in plasmas (PIII or PSII) generated either by DC or (13.56 MHz) RF sources. Thus, a fully automated electromechanical system has been designed and constructed on the basis of guard double electric probes in order to prevent both probe erosion and plasma contamination. The electronic components of the system comprise a ± 150 V triangular and ramp wave form generator capable of supplying ± 50 μA to ± 100 mA currents at 1–2000 Hz frequencies and a DAQ PCI-6023E data acquisition board with a 12 bit resolution compatible with LabVIEW graphic language. A program has been specifically developed for the latter in order to control the probe position within the discharge vessel and to capture, filter, visualize, process and store the respective information. The system has been experimentally applied to DC and RF plasmas of helium, argon, nitrogen, oxygen, and multiple gas mixtures with great success, inside several PIII reactors. Results are presented free from RF interference from the process itself or other surrounding sources.

The design and construction of a 13.56-MHz RF power amplifier has been carried out on the basis of a modified resonant LC circuit in parallel regarding to the classic E-class amplifier LC series resonant circuit; this was done in order to take advantage of the operation characteristics of the resonant capacitor as a bidirectional voltage source. Therefore, the parallel LC circuit amplifies the voltage signals which can be applied to resistive or capacitive-resistive loads without the need for an impedance matching network, conventionally used with plasma generators. The main achievement of the described instrumentation lays in its constant response under a wide interval of load impedance. This facility has been applied to the generation of steady discharges in plasma needle appliances and both parallel plate and coaxial dielectric barrier discharge (DBD) reactors. Some relevant results of the DBD sterilization of four different kinds of microorganisms are included, showing the feasibility of the technique within reduced processing times, under 80 s in all the cases.

Films of titanium dioxide (TiO 2 ) in the rutile and anatase phases have been obtained in a cylindrical pyrex-like glass vessel inductively coupled to a 13.56 MHz radio frequency generator. Rutile films were developed from commercially pure (CpTi) titanium samples used as targets in an argon/oxygen plasma. Each CpTi target was biased at − 3000 V by means of a direct current supply. The plasma ion acceleration at such a potential leads to a kinetic energy transference to the target whose temperature rises to ∼ 670 °C, favourable to the rutile formation. The anatase films were obtained from sputtering the titanium targets over glass and silicon electrically floated substrates. The latter were placed 3 cm away from the target. The substrates attained a temperature resulting from the amount of heat transferred by the plasma particles, in turn, a function of the plasma parameters. Thus, under the prevailing experimental conditions, substrate temperatures lay in the ∼ 280 to 325 °C range. Atomic titanium is assumed to be sputtered out of the target and oxidised, evolving into the anatase phase on the surface of the glass or silicon. The obtained film phases did not require annealing after the plasma oxidation process. The characterisation of the film samples was conducted by means of X-ray diffraction (XRD), Raman spectroscopy and scanning electron microscopy (SEM).

The design, instrumentation and early operation results of a digitally controlled voltage source inverter (VSI) are described. This inverter has been structured from a three cell flying capacitor inverter (TCFCI). Two different inverter control modes – open-loop and closed-loop – are applied by a digital system based on a Texas Instrument TMS320C6713 digital signal processor (DSP) board. The VSI is able to generate AC voltage signals up to 120 V amplitudes at a maximal 6 A current, from ∼9 kHz to ∼60 kHz in ∼900 Hz steps in both controls by varying the signal period through the square-wave command strategy. The multi-cell structure of the inverter provides an output frequency nearly three times that of the TCFCI semiconductor commutation. The power output of the TCFCI can drive a high frequency step-up transformer which, in turn, is associated with a cylindrical reactor where dielectric barrier discharges (DBD) are conducted.

It is not easy, in general, to improve the mechanical properties of aluminium alloys by traditional nitriding methods. By contrast, plasma immersion ion implantation (PIII) has been successfully used for hardening and in wear resistance improvement. The present work sets out to investigate the formation of AlN on 6061T6 aluminium samples by the PIII process at low energy (2–6 keV) with ion doses in the order of 1018 ions/cm2 and from nitrogen–argon mixtures at different concentrations (N70–Ar30, N50–Ar50 and N30–Ar70) maintained at ∼400 °C sample temperatures. The outcome was evaluated by X-ray diffractometry, scanning electron microscopy, Vickers microhardness tests and profilometry.

Samples of pure titanium have been treated by means a plasma immersed ion implantation (PIII) process in a DC glow discharge in pure oxygen and in different nitrogen-oxygen mixtures. In contrast with conventional voltage supply based glow PIII, the present study has been conducted with a novel specifically designed high current supply which allows a high electron density to be kept constant, regardless of gas pressure variations, within the operational ranks. Thus, the acquired sample characteristics can be more clearly ascribed to the chemical composition of the mixture. One stratified TiO2 (rutile) and TiN0.26 layer was identified from XRD and Raman spectroscopy, both of these compounds reputedly being highly biocompatible. The superficial hardness of the samples was improved up to more than five times that of the untreated reference sample, namely, ∼1600 Vickers microhardness (10 g load) thanks to a 2–6 μm deep implanted layer. These optimal results have been obtained from an 80% nitrogen 20% oxygen mixture at 1×10-2 torr. Furthermore, with this gas proportion, the best roughness finishing of the sample set was accomplished, which can be relevant for biocompatible applications.

A study of the plasma ion implantation (PIII) of commercially pure titanium (CpTi) at a low voltage (

This paper presents a model of the typical dielectric barrier plasma discharge at atmospheric pressure, structured as an equivalent electric circuit whose elements are identified with, and deducted from, the main influential variables of the process, namely, the applied gas, the geometry of the reactor, the breakdown parameters, as well as the power supply associated to the dielectric barrier discharge cell. Considering a parallel-plate reactor and a high-voltage sinusoidal power supply, an electrical comprehensive Simulink/MATLAB model has been developed in order to reveal the interaction between these two elements. The main components of this discharge model are as follows: (1) a double dielectric capacitance; (2) a voltage-controlled current source; and (3) a gas capacitance associated to the ionized gas. A sinusoidal voltage of up to 15 kV peak to peak at frequencies of 12.5 and 47 kHz has been applied to the discharge electrodes. The electrical model is based on the power law proposed by Roth, which defines the V-I behavior during the discharge startup. A series of simulations has been carried out in order to estimate the total current and voltage consumed during each discharge and to identify those parameters which are not measurable during the process. Finally, both the experimental and simulated voltage and current results in helium, argon, and nitrogen, as well as their Q-V graphics, are shown, and a comparison between them is discussed.

A new RF power supply intended for low-power plasma torches is presented. It is based on a class-E amplifier, modified on the principle of a parallel LC resonant circuit, and is used here to supply the so-called 'plasma needle'. The latter is matched with a shunt inductor, and both are connected in parallel to the resonant capacitor C. This configuration is particularly useful for the control of stable discharge characteristics, for example, to resist naturally occurring variations in the load impedance, by providing the high voltage necessary to ignite and maintain the plasma. The overall system has been tested at atmospheric pressure by producing glow discharges in flows of helium and argon. We present early results that describe the device's characteristics.

We present some results obtained from nitriding of AISI 304 stainless steel substrates. The process take place in an inductively coupled plasma discharge supplied by a ∼300 W source at 13.56 MHz in a 85% hydrogen and 15% nitrogen gas mixture. The samples, placed into a pyrex glass discharge chamber (3.5 cm diameter and 60 cm long) were biased by DC power from 0 to −300 V with respect to ground. The resulting hardness is a function of the increasing nitrogen concentration in the substrate and this, in turn, of the temperature which varied from 200 to 470 °C. After nitriding at −300 V, hardness values of 1790 HV under 10 g loads and of 632 HV for 300 g were measured. X-ray diffraction indicates that the expanded phase amplitude (γN) depends on the substrate temperature.

Titanium surface oxidation deserves a growing interest in biomedical engineering due to its biocompatibility enhancement and mechanical performance. In this work we report on the Ti surface modification, conducted into a toroidal vacuum vessel, by a DC plasma formed by an oxygen-argon (20/80) mixture. By varying the gas pressure within the 2.5 to 5×10–3 mbar interval at the sample bias voltage –3000 V, we have gained control over the sample temperature up to the order of 650°C. In turn, the composition of the modified surface has been controlled by adjusting the flow rates of the gas mixture and the above mentioned temperature. The samples were characterised by microhardness tests, SEM, XRD and Raman spectroscopy. The diagnostics revealed a rutile TiO2 and TiO1.04 phase content in the modified layer. The remarkable effects of Ti sample temperature and treatment time on the morphology of the surface structure were explored. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

In this paper, we present a model (which is structured as an equivalent electric circuit whose elements are identified and deducted from the nature of the medium, the ionization and expansion process of the streamers that convey the prebreakdown current, and the energy associated to the electric breakdown in water) and a simulation of a pulsed corona discharge (PCD). Considering this, a coaxial reactor and an inexpensive and compact high-voltage pulsed-power supply (PPS) system were designed and constructed with the purpose of carrying out the PCD experimentally. The simulation results enable the prediction of the behavior of the discharge. The coaxial reactor is constituted by a cylindrical chamber and a straight central rod. The PPS operates within the 100-2000-Hz repetition rate and 0-30-kV amplitude ranges. All the system has been tested, and the first electrical results, voltage, and current waveforms, are presented.

We present in this work some experimental results obtained from nitriding AISI 304 stainless steel at different temperatures by means of RF/DC generated 10 15 m −3 density plasmas in the 1–4 eV electron temperature range. The samples were biased up to −400 V. Substrate temperatures have proved to be an influential factor in the diffusion of the ions impinging onto the material under treatment. In turn, the γ N shift expansion observed by XRD during this temperature increase is a function of the amount of nitrogen introduced to the sample and is related to the bias, the nitrided layer depth and the plasma characteristics. Thus, we have identified the substrate temperature as a global control variable in order to analyse the evolution of the nitrogen enrichment process through its influence on the X-ray diffraction imaging of the γ N shift in the samples. The optimization of the temperature is explored along with its limits in terms of the Cr precipitation threshold.

Better protective and functional coatings on dental drills are increasingly demanded for their desired mechanical, tribological or chemical properties. We have studied the surface modification of steel dental drills, with an aim to increasing both their cutting life and corrosion resistance in dentistry using low-energy plasma-immersion nitrogen implantation over different temperature ranges. The temperature of the drills was controlled by varying the implantation voltage. Following implantation, tests showed that the microhardness of the nitrided drill surfaces was approximately one order higher than that of untreated drills and the corrosion tolerance was found to increase with growing temperature of the plasma-immersion process.

Dielectric barrier discharge cells (DBDCs) have proved their efficiency in the generation of cold plasmas for hazardous organic compound degradation. Here, we describe the design and construction of a dual thermal packed-bed reactor and DBDC-based system to carry out the degradation of hazardous organic compounds in both liquid and gas phases. The main components of this system are: (i) the thermal treatment system, (ii) DBDC and (iii) resonant inverters of low (3.3 kHz) and high (100 kHz) calculated frequencies. The definition of the cell physical parameters considers: (a) a first-order degradation ratio of the compound and (b) the air breakdown at atmospheric pressure as a function of the transport carrier gas. The power consumed by the cells during the discharges was computed theoretically and experimentally. Using the dual system along with a gas chromatography diagnostic system, highly efficient degradations of a test compound (benzene) have been obtained, reaching 99.950% in the case of a cell experimentally operated at 3.3 kHz and up to 99.996% in another one at 94.3 kHz. An additional 3.7 times reduction in the latter case residence time with respect to the low frequency cell has been found.

In this paper, the design and construction of a high-voltage high-frequency serial resonant bridge inverter endowed with a fast resonant frequency following capability, using the digital phase locked loop (DPLL) technique, is described. The main characteristics of this inverter are: high voltage (10 kV), high frequency (94.3 kHz), and low losses in the commutation devices. This inverter is used for the excitation of a dielectric barrier discharge cell (DBDC) for cold plasma generation. The system has been applied in hazardous organic compound degradation. In particular, benzene has been degraded to the order of 99.85%, according to measurements obtained by gas chromatography.

A study is reported of the influence of both temperature and nitrogen gas pressure on the microhardness and corrosion resistance of AISI 304 stainless steel, PIII treated in a DC plasma discharge in a toroidal chamber. The sample temperatures were stabilised at various gas pressures within the range 1×10 −3 to 2×10 −1 mbar by adjusting the pulse duration (50–75 μs) while maintaining constant the bias voltage (−5 kV) and pulse frequency 1 kHz. It was found that treatment below ∼520 °C substantially enhances the microhardness as well as the corrosion resistance of the samples. The experiments also showed that treating the samples at temperatures above ∼520 °C adversely modifies the properties associated with corrosion resistance.

The annealed low alloy 4140 steel samples have been nitrided for di erent treatment periods (1 6 h) in an RF inductive plasma discharge with very low bias voltage (≈ 400 V). The resulting nitrided layer has been observed by means of an optical microscope whereas the nitride phases have been characterised by X-ray analysis. The corrosion response, assessed by the potentiodynamic tests in the 3.5% NaCl solution, presents both higher noble potential values and lower corrosion rates when compared with the untreated sample. The Vickers microhardness tests values show an appreciable increment compared to that of the untreated sample. The process is characterized by a high overall e ciency because similar average Vickers tests values were obtained, no matter for how long the treatment was extended. Likewise, the scanning electron micrographs con rmed no appreciable size evolution of the compound layer microstructure at di erent times of treatment.

One alternative application in the decomposition and destruction of volatile organic compounds (VOCs) by a silent plasma dielectric barrier discharge (DBD) has been successfully accomplished. For this purpose, we have designed and constructed two pairs of cells, of rectangular and circular geometries, 333.96 cm³ each cell, and a similar second pair of 62.25 cm³ each one. Resonant inverters for low (3.3 kHz) and high (100 kHz) frequencies were also designed and applied to these cells. The specification of the main physical parameters of each cell contemplates: i) a first order degradation ratio of the compound, and ii) air breakdown at atmospheric pressure as a function of the carrying gas. The power consumed by the cells during the discharges was computed both theoretically and experimentally by Manley's method. The equipment was applied to the degradation of toluene, which has been degraded by an oxidation process in air-oxygen and argon-oxygen gas mixtures at atmospheric pressure within the cells. The destruction efficiency was measured as a function of the initial concentration. When air is used as an oxidant, a clear formation of solid products on the walls of dielectric glass plates has been observed, such deposits being polymeric in nature. These deposits seem to be responsible for a decline in the degradation efficiency of the treated compounds.

Optimal surface nitriding is closely related to plasma chemical composition. The effects of Plasma-Immersion Ion Implantation (PIII) nitriding with 15% N 2 +85% H 2 type mixtures have been studied. A simplified PIII facility was assembled around an evacuated Pyrex cylindrical 500 mm long reactor with a 190 mm inner diameter, over which a 3.2 mm wide antenna was coaxially wound with a 240 mm inner diameter. The system was supplied by a 13.56 MHz RF generator whose electric component developed the plasma discharge. After the admission of the gas mixture to the reactor vessel the breakdown took place within 5–15 Pa work pressure and 450–500W RF power. The main plasma parameters were characterized including a 1.8 × 10 18 to 3.1 × 10 18 m −3 density by means of double Langmuir probes. An additional DC power supply was selected in order to bias AISI 304 stainless steel samples with a view to improving the steel hardness properties without compromising its corrosion resistance. The samples treated at different temperatures and for several periods, were evaluated by means of X-ray diffraction (XRD), which indicated the formation of nitrides, identified as Fe 3 NiN and FeNiN and can be associated with the enhanced austenitic phase of the stainless steel. Scanning electron microscopy (SEM) assessed the atomic percentages of nitrogen both on the sample surface and through their cross-section. Vickers microhardness (HV) tests exhibited up to a 6–7 times increase at a 500g load. Finally, Raman spectroscopy studies established four active modes at 215, 267, 385 and 490 cm −1 with temperatures between 400 and 500 °C.

We present a study on the surface modification of dental tools by nitrogen PIII with a view to increasing both their cutting life and corrosion resistance. The treatment temperature was selected between 350 and 500 °C, every 50 °C, being controlled by varying the pulse duration in order to determine the improvement of the material performance after implantation. The tools were additionally characterized by Knoop microhardness measurements, SEM, XDR and electrochemical corrosion tests which, in all, pointed to an abundance of the supersaturated iron phase accompanied by considerable increases in microhardness and yet, with a slightly enhanced corrosion resistance. Furthermore, the formation of the associated expanded austenitic phase appears to enhance the corrosion resistance of the untreated drills.

The aim of this study is to determine the toxic and genotoxic damages produced by a helium plasma needle upon HeLa and E. coli (OG100 and PQ30) cell cultures. For HeLa cells survival (MTT) and microelectrophoresis comet) assays were performed; meanwhile in E. coli, viable count and genotoxicity by the chromotest were evaluated. The outcomes indicate that the plasma exposures on HeLa cells undergo more toxicity and genotoxicity as treatment time increases. With respect to E. coli, plasma exposure generated toxicity, but no genotoxicity could be detected with this system. In the strain OG100, defective in a protection mechanism to oxidizing agents, there was a reduction in the survival of one order of magnitude compared to the wild type strain PQ30. It suggests that such reduction is due to the plasma by means of the reactive oxygen and nitrogen species (RONS) generated during atmospheric air interaction.

An experimental study of ATCC (American Type Culture Collection) 8739 Escherichia coli bacteria inactivation in water by means of pulsed dielectric barrier discharge (PDBD) atmospheric pressure plasmas is presented. Plasma is generated by an adjustable power source capable of supplying high voltage 25 kV pulses, ∼30 μs long and at a 500 Hz frequency. The process was conducted in a ∼152 cm 3 cylindrical stainless steel coaxial reactor, endowed with a straight central electrode and a gas inlet. The bacterial concentration in water was varied from 10 3 up to 10 8 E. coli cells per millilitre. The inactivation was achieved without gas flow in the order of 82% at 10 8 colony-forming units per millilitre (CFU mL –1 ) concentrations in 600 s. In addition, oxygen was added to the gas supply in order to increase the ozone content in the process, raising the inactivation percentage to the order of 90% in the same treatment time. In order to reach a higher efficiency however, oxygen injection modulation is applied, leading to inactivation percentages above 99.99%. These results are similarly valid for lower bacterial concentrations. A. N. Hernandez-Arias B. G. Rodriguez-Mendez (corresponding author) R. Lopez-Callejas D. Alcantara-Diaz R. Valencia-Alvarado A. Mercado-Cabrera R. Pena-Eguiluz A. E. Munoz-Castro

Aluminium is the third more abundant element in the Earth crust. The metal exhibits useful properties such as low density, high strength, good formability and a high resistance to corrosion. Aluminium can gain significant mechanical strength by means of alloying, whereby it is the most used metal after steel. In this sense, aluminium properties depend on its purity and its crystalline structure is face centred cubic [Wang et al, 1999]. Aluminium is, among other characteristics, malleable, easily machined and very ductile. Its high sensitivity to oxidation endows it with a waterproof passivation layer, typically 5-20μm thick according to the prevailing humidity, considerably adherent, which contributes to corrosion tolerance and general durability. The passivation layer consists of the amphoteric aluminium oxide Al2O3, often known as alumina or aloxite in mining and materials science. As corrosion is a major source of failure in Materials Engineering, aluminium is an obvious choice to face aggressive environments, including the atmospheric one. Aluminium as a pure element has a low mechanical resistance which prevents its application under deformation and fracture conditions. Thus, low density combined with good resistance make aluminium alloys very attractive in design considerations. The properties of these alloys depend on a complex interaction among chemical composition, microstructural failures in solidification, thermal treatments, etc. although an increase in the alloy content tends, in general, to diminish the tolerance to corrosion. That is why quenching processes have been developed to improve the response to corrosion of highly alloyed materials. It is essential to select the precise alloy to match the resistance, ductibility, formability, solubility, corrosion tolerance, etc., required by an application. Modifying aluminium composition by the adding nitrogen in an ion implantation process provides the treated samples with surface hardness and improved tribological properties by heating them in a nitrogen rich atmosphere. In this way, at low doses, aluminium nitride (AlN) becomes structured in the shape of clusters, the nitride content clearly increasing with the dose. Ion implantation is applied to pieces subjected to major friction and load forces such as rolling tracks, cylinder sleeves, etc., which require some core plasticity enabling