Institute of Fundamental Technological Research

The article presents research on finishing treatment applied to components made of Inconel through 3D printing by Laser Powder Bed Fusion method. Vibration-abrasive machining was carried out using a supporting fluid and various shapes of abrasive. The effects of the processing conditions were analysed based on the surface roughness of the samples and mass loss. The obtained collective results were subjected to comparative analysis with the effects of vibratory-abrasive processing without the use of a processing fluid, as presented in the article. The research has shown that using vibration-abrasive processing, it is possible to reduce the height of surface irregularities by more than three times after four hours of treatment. The intensity of processing was the highest in the first hour of the process. The lowest roughness heights Ra = 1.8 μm were obtained using ceramic balls in the presence of a supporting fluid.

vibration-abrasive processing, IN939, roughness, additive manufacturing, 3D printing post-processing

We present the deposition and characterization of tungsten-tantalum diboride (W,Ta)B2 coatings prepared by the high-power impulse magnetron sputtering technique. We evaluated the influence of pulse duration and substrate bias on the properties of (W,Ta)B2 films. A high hardness of up to 35 GPa measured by nanoindentation was simultaneously obtained with good elastic properties. Changing the pulse duration greatly affected the B/(W+Ta) atomic ratio, which influenced the properties of the coatings. The deposited films are thermally stable at up to 1000 ◦C in vacuum and are able to withstand oxidation at 500 ◦C.

tungsten diboride, high power impulse magnetron sputtering (HiPIMS), hardness, thermal stability, oxidation resistance

In this work, significant strength and ductility variations are reported for AlSi10Mg parts fabricated at different orientations using laser powder bed fusion (LPBF). Hardness and surface roughness of the specimens at different orientations were measured. Tensile testing together with digital image correlation technique were conducted on the specimens. XY specimens showed the highest yield stress and ultimate tensile strength while XZ specimens showed the highest ductility. Hardness measurements for different specimens were in accordance with the tensile test results, following the same order as the UTS values, XY specimens being the highest and XY-45° (out-of-plane) specimens being the lowest. Fractography of the broken surfaces of the specimens under tensile testing revealed the microstructural features and various defects in the tensile fracture. The anisotropy in mechanical properties is attributed to the microstructural anisotropy as well as presence of various types of defects induced by the AM process, which affects the deformation and failure mechanism of the parts. Linear relationships between experimental Vickers hardness versus yield stress and UTS measurements were developed. In case of material selection for different applications, these relationships can be used as a simple tool for converting hardness and yield stress (or UTS) values to each other. An equivalent strain-hardness relationship was also proposed which can be used for health monitoring of parts subject to tensile loading.

Laser powder bed fusion, Hardness, Mechanical properties, Defects, Microstructure

The article presents theoretical and experimental study of shock waves induced by a nanosecond laser pulse. Generation of surface plasma pressure by ablation of the graphite absorption layer in water medium and shock wave formation were analyzed theoretically and experimentally. The amplitude and temporal variation of the shock wave pressure was determined basing on a proposed hydrodynamic model of nanosecond laser ablation and experimentally verified with use of a polyvinylidene fluoride (PVDF) piezoelectric-film sensor. The determined pressure wave was used for examination of adhesive strength of tungsten–zirconium–boride coatings on steel substrate. The magnetron sputtered (MS) W–Zr–B coatings show good adhesion to the steel substrate. The obtained experimental results prove the correctness of the proposed model as well as the suitability of the procedure for assessment of adhesive strength.

laser pulse, shock wave, MS coatings, ternary borides, laser adhesion test

To enhance the properties of tungsten diboride, we have synthesized and characterized solid solutions of this material with chromium, molybdenum, rhenium and zirconium. The obtained materials were subsequently deposited as coatings. Various concentrations of these transition metal elements, ranging from 0.0 to 24.0 at.%, on a metals basis, were made. Spark plasma sintering was used to synthesize these refractory compounds from the pure elements. Elemental and phase purity of both samples (sintered compacts and coatings) were examined using energy dispersive X-ray spectroscopy and X-ray diffraction. Microindentation was utilized to measure the Vickers hardness. X-ray diffraction results indicate that the solubility limit is below 8 at.% for Mo, Re and Zr and below 16 at.% for Cr. Above this limit both diborides (W,TM)B2 are created. Addition of transition metals caused decrease of density and increase of hardness and electrical conductivity of sintered compacts. Deposited coatings W1−xTMxBy (TM = Cr, Mo, Re, Zr; x = 0.2; y = 1.7–2) are homogenous, smooth and hard. The maximal hardness was measured for W-Cr-B films and under the load of 10 g was 50.4 ± 4.7 GPa. Deposited films possess relatively high fracture toughness and for WB2 coatings alloyed with zirconium it is K1c = 2.11 MPa m^1/2.

ternary tungsten boride, spark plasma sintering, magnetron sputtering, electrical conductivity

The article presents a study of shock waves induced by a nanosecond laser pulse in samples in the form of steel plates. Its contents include a description of the measurement system, methods of calculations and some characteristics of the measuring instruments and materials used. The quoted formulas enabled the processing of recorded measurement signals. The influence of material used as a confining layer (glass, PMMA - Plexiglass, water) and substrate (PMMA, aluminium, steel) on the amplitude and shape of recorded pressure waves was studied. Pressure behind the shock wave measurements were conducted using piezoelectric polymer PVDF (polivinylidene fluoride) sensors. Verifications of PVDF results were conducted by the measurements of velocity of back sample surface by VISAR (Velocity Interferometer System for Any Reflector). A qualitative compliance between the PVDF's pressure and VISAR's velocity rescaled to pressure was achieved. The strains (about 0.3%) and strain rates (about 3 × 10^5 1/sec) were evaluated. The obtained results will allow for a better selection of test conditions for studying material properties by using a shock wave induced by the laser pulse.

laser pulse, shock wave, PVDF sensor, VISAR

In this work, α-WB2 and (W,Ti)B2 borides were applied as wear-resistant coatings to commercial WC–Co cutting inserts. Properties of coatings deposited by magnetron sputtering on WC–Co tools were studied. The crystal structure and chemical composition were analyzed. Vickers hardness and surface roughness were determined and wear test in semi-dry conditions was performed. The W–B and W–Ti–B coatings deposited on WC–Co substrate were smooth and very hard. However, titanium alloy W-B films with Vickers hardness of 3630 ± 260 HV0.02 were characterized by lower adhesion to the substrate, influencing the wear mechanism. Turning tests carried out on 304 stainless steel showed that the W–B film caused less wear compared to uncoated insert. Moreover, when W–B coating was applied, flank wear was reduced by 30% compared to uncoated WC–Co insert. Additionally, coating prevented chipping of the edge during cutting under test conditions. The research shows that W–B film deposited by magnetron sputtering has great potential as a coating for cutting tools for difficult-to-cut materials.

PVD coatings, wear resistance, transition metal borides, cutting tools

Experimental and numerical tests of surface plastic deformation generated under different strain rates were performed. Deformations were introduced by both classical Brinell and laser pulse hardness tests. An Nd:YAG laser with a wavelength of 1064 nm and a laser pulse time length of 10 ns was used to generated a shock wave to induce local plastic deformation on the material surface. The laser pulse induces a repeatable plastic deformation of a surface without thermal effects on the surfaces. Based on imprint geometry, the dynamic hardness of materials was evaluated at a strain rate of the order 107 s-1. Numerical analyses carried out included quasi-static and dynamic Brinell hardness tests and laser pulse interactions with materials. The Rusinek-Klepaczko constitutive model applied in the calculations allows the prediction of the mechanical characteristics at a strain range strain range from 10 to 4 s-1 to 107 s-1. Numerical and experimental results from the surface plastic deformations show close agreement.

laser pulse, dynamic hardness, plastic deformations, metals

The laser spallation technique was applied for measurement of residual stress and adhesion of thin films. Two films of different properties, ductile and soft Ti, and hard and brittle TiN, were studied. The films were produced on 304 steel substrate by PVD method. The residual stress value obtained by laser spallation technique LST were compared with stress value from X-ray diffraction method. Good agreement of stress values measured by both methods was attained. Additionally, the interface strength of the films was tested by laser adhesion spallation technique LASAT with use of VISAR system. It was shown that shock wave induced by a nanosecond laser pulse adequately determines properties of PVD thin films on metal substrate

Laser spallation technique, Residual stress, Adhesion, Thin layer, PVD, VISAR system

The plasma induced during underwater pulsed laser ablation of graphite is studied both experimentally and theoretically. The results of the experiment show that the maximum plasma temperature of 25000 K is reached 20 ns from the beginning of the laser pulse and decreases to 6500 K after 1000 ns. The observed OH absorption band shows that the plasma plume is surrounded by the thin layer of dissociated water vapour at a temperature around 5500 K. The hydrodynamic model applied shows similar maximum plasma temperature at delay times between 14 ns and 30 ns. The calculations show also that already at 14th ns, the plasma electron density reaches 0.97·1027 m−3, which is the critical density for 1064 nm radiation. At the same time the plasma pressure is 2 GPa, which is consisted with earlier measurements of the peak pressure exerted on a target in similar conditions.

underwater laser processing, pulsed laser ablation in liquid, laser induced plasma, numerical modelling

The paper presents result of experimental and numerical tests of plastic deformation of austenitic steel generated by a nanosecond laser pulse. The shock wave generated by the laser pulse was used to induce local plastic deformation of the material. The study examined the possibility of using the process to develop a laser forming of materials under ultra-high strain rate. It has been shown that the laser pulse with intensity 2.5 GW/cm2 induces a repeatable plastic deformation of commercially available 304 steel without thermal effects on the surface

Laser pulse, Plastic deformations, Microstructure, Numerical simulations

Fatigue loading induces a microstructure evolution leading to the change of macroscopically observed mechanical behavior of a dual phase DP500 steel. It was assumed that stress–strain characteristic of a pre-fatigued material may be determined using constitutive equation taking into account damage parameter. To estimate development of the fatigue damage in specimen a variation of the inelastic strain component was applied.

The flat „dog-bone” specimens were initially loaded using stress controlled cycles. When the strain reached a given value the fatigue process was stopped. Subsequently, the specimens with introduced fatigue damage were subjected to tensile tests. Next, the Johnson-Cook's constitutive equation was calibrated separately for each pre-fatigue case. Finally, a new constitutive relationship, based on the Johnson-Cook's model was proposed. It reflects the hardening and softening effects by taking into account both a change in the dislocation structure and development of fatigue microdamage. Proposed model shows a very good agreement with experimental data.

Constitutive model, Dual-phase steel, Fatigue, Stress–strain curve, Fatigue damage, Inelastic strain

W pracy przedstawiono analizę stanu warstwy wierzchniej po laserowym stopowaniu stali Stellitem 6 oraz obróbce hybrydowej łączącej laserowe stopowaniem z obróbką nagniataniem. Obróbka hybrydowa prowadzona była na stanowisku laserowym. Do realizacji procesu nagniatania powierzchni wykorzystano głowicę do nagniatania ślizgowego umożliwiającą obróbkę w podwyższonych temperaturach jak i na zimno. Ocenę efektów obróbki hybrydowej przeprowadzono na podstawie badań chropowatości, mikrostruktury, mikrotwardości oraz badań naprężeń własnych.

stopowanie laserowe, nagniatanie, obróbka hybrydowa

Obok wielu różnych zastosowań, promieniowanie laserowe jest stosowane również szeroko w przemyśle do powierzchniowej obróbki różnych materiałów z wykorzystaniem procesów ablacji laserowej. Tematyka ta jest bardzo szeroka. Zespół autorów prowadzi od wielu lat badania nad zastosowaniem powierzchniowej obróbki laserowej w tak różnych obszarach jak konserwacja zabytków (czyszczenie laserowe) czy bioinżynieria (kształtowanie powierzchni implantów). W niniejszym artykule przedstawiono pewien wycinek prac zespołu, związany z opracowaniem laserowej metody badań adhezji cienkich warstw i laserową obróbką materiałów do zastosowań w mikro-przepływach i separacji komórek krwi. W pierwszym przypadku, padające na powierzchnię intensywne promieniowanie laserowe wytwarza silną falę uderzeniową w badanych materiale, pozwalającą określić progowe wartości uszkodzenia warstw technologicznych. Badania uzupełnione są przez modelowanie teoretyczne towarzyszących zjawisk fizycznych. W drugim przypadku uwagę zwraca możliwość separacji krążących komórek nowotworowych na laserowo wykonanych mikrositach, zawierających setki tysięcy otworów o średnicach na poziomie 10 μm na obszarach o obwodzie kilkunastu mm. Wymiary mikro-sit pozwalają na ich umieszczenie w układach mikro-przepływowych.

mikro-obróbka laserowa, fale uderzeniowe, grawerowanie szkła, cięcie szafiru, wytwarzanie mikrosit

Reactive spark plasma sintering (SPS) of WB2/WB3 ceramics from elements is studied; the sintering pressure dependence of the ratio of WB3 to WB2 in samples produced by SPS is discussed. Regardless of the sintering pressure, the obtained samples are very hard ~20 GPa. WB3 superhard films prepared by pulsed laser deposition (PLD) from selected SPS targets are presented.

WB3 coatings were prepared on Si (100) substrates using a nanosecond, Nd:YAG laser operating at a 355 nm wavelength. The phase analysis, crystallography, and orientations have been studied using X-ray diffraction (XRD). A WB2 to WB3 phase transformation from 8.2% WB3 in a sintered target to 93.3% WB3 in a deposited film was observed. Additionally, the surface of a SPS sintered WBx target after the ablation process was examined. XRD studies show that already during the laser ablation there is a significant WB2 to WB3 phase transformation. Vickers hardness of sintered samples was measured in macro- and micro-scale, and PLD films in the nanoscale.

Films, Tungsten borides, SPS – sintering, Pulsed laser ablation/deposition

Taylor impact tests in the classic and symmetric configurations were applied to analyse the development of plastic deformation and damage in Al-6082-T6 rods. Deformation histories during impact were recorded using high-speed photography, while internal axial damage was identified using metallography. The axial damage observed during the symmetric test were initiated during stress triaxiality peaks under tensile loading conditions. Variations of the stress state are the result of superimposed lateral mechanical waves reflected from the perimeter of the specimen. The fracture strain decreases with the increase of the stress triaxiality; it is thus possible to initiate damage at relatively low strain values under high-stress triaxiality values. During classic Taylor test because of the deflection of the elastic steel anvil in the rod on anvil test, the oscillations are smaller and quickly damped in comparison to the rod on rod experiment. Therefore, the initiation of axial damage is impossible. The cracks on the specimen edge are due to tensile loadings. For both the symmetric and classic Taylor tests, the damage conditions are comparable, i.e., a stable increase of strain combined with tensile loadings.

Taylor impact, Numerical modelling, High-speed photography, Damage initiation, Constitutive relation

The analysis involved subjecting DP 500 steel to pre-fatigue loads, and then tension at high strain rates using Hopkinson bar. Digital image correlation method was used to investigate how the pre-fatigue loads change the strains’ distribution on the surface of the sample subjected to tension. The analysis involved both films recorded at low rates of deformation (1.0 × 10−2 s−1) using ARAMIS system and the images captured with a high-speed camera during dynamic deformations with a Hopkinson bar (6.0 × 102 s−1). It was noted, based on the micro-structural analysis, that pre-fatigue loads cause the formation of micro-damages in the examined material. Thus, macroscopically observed stress–strain characteristic as well as Huber–Mises substitute strains’ distribution determined locally by the image correlation method is also subject to changes. The observed effects include the following: reduction of deformation corresponding to the tensile strength, decrease in elongation at break, and increase in yield limit and tensile strength. The observed effects are intensified with an increased stress value and pre-fatigue cycles’ number. Furthermore, these phenomena are more intensive in the conditions of dynamic deformation.

Hopkinson bar, fatigue, viscoplastic response, damage, stress–strain, tensile, high strain rate

Przedstawiono wyniki badań eksperymentalnych procesu hartowania laserowego stali 45. Do badań wykorzystano laser Nd:YAG pracujący w trybie ciągłym. Przeprowadzono analizę wpływu strategii obróbki na jej efektywność. Energochłonność procesu analizowano na podstawie wielkości strefy zahartowaniej uzyskanej w wyniku zastosowania pojedynczego przejścia wiązki laserowej, skanowania powierzchni i obróbki z oscylacyjnym ruchem wiązki względem materiału. Stwierdzono znaczące zwiększenie efektywności procesu w warunkach nagrzewania oscylacyjnego.

obróbka laserowa, hartowanie powierzchniowe, oscylacje

This letter describes modelling and experimental results of low and high pressure shock waves (of the order of 100 and 1000 bar, respectively) induced by pulse laser radiation. Measurements were performed using piezoelectric polymer PVDF sensors. The results of numerical calculations and their comparison with an experiment have been posted. Measured and calculated results have been used in estimation of the temporary course of signals from a fibre VISAR interferometer which measured the movement velocity of a steel plate driven by the analysed shock waves. The description is supplemented with the results of magnitude measurements of surface plastic deformation and material microstructure of samples.

In this paper the simultaneous laser melting and burnishing of a stainless steel is studied both experimentally and theoretically. A continuous CO2 laser beam is moving either along a straight line or criss-crossing it. It has been shown that the oscillatory movement of the laser source together with the burnishing results in a better surface topography comparing to the non-oscillatory process. A theoretical modelling is applied to calculate the temperature field during the process. Theresults oftheoretical analysis are verifiedbyanalyzing microstructure changes of the material in laser heated zone. It has been found that a very good agreement between theoretical and experimental results is achieved when the change of the absorptivity of the laser beam with the temperature of the melted zone is taken into account.

laser treatment, hybridtreatment, surface structure, mathematical modelling

W pracy przedstawiono wyniki badań mikrostruktury materiału i odporności na zużycie ścierne warstw Stellitu wytworzonych metodą: natrysku plazmowego, stopowania laserowego oraz poprzez obróbkę hybrydowa łączącą proces stopowania laserowego z nagniataniem powierzchniowym. Obróbkę laserowo – mechaniczną przeprowadzono dla przypadku laserowego stopowania stali 0N18N9 Stellitem 6. Do procesu stopowania wykorzystano ciągłą wiązkę laserową CO2 o mocy 2 kW, nagniatanie powierzchniowe – mikro-młoteczkowanie prowadzono jednocześnie z modyfikacją laserową w podwyższonej temperaturze. Mikrostrukturę materiału analizowano na mikroskopie optycznym oraz na SEM. Określono wielkość strefy przetopionej, stopień zgniotu powierzchniowego. Do badań odporności na zużycie ścierne wykorzystano tester tribologiczny T - 01M typu trzpień - tarcza. Stwierdzono dobrą odporność na zużycie warstw po obróbce hybrydowej

The experimental identification of fatigue damage mechanisms and evaluation of their development rate, based on changes in material respond on cycle loading, has been presented in the work. The research has been conducted on hyper-eutectic cast alloy AlSi8Cu3. The microstructure and fracture analyses were performed. The high cycle fatigue tests were conducted with frequency of 20 Hz under constant nominal stress amplitude with monitoring the strain response of material during the test. The ratcheting was found as the main mechanism of the fatigue damage. It was established that the linear fatigue accumulation law should not be used for fatigue life prediction in case of the tested cast aluminum alloy

Cast aluminum alloy, Fatigue test, Fatigue damage

The paper will present results of the research on the surface layer condition/integrity after ultrasound treatments supported by the electrodischarge coating (EDC). Features determiningthe product quality like geometric structure of the surface, microhardness or metallographic microstructure will be evaluated. The assumption of ultrasonic treatment introduction during EDC is stabilization of the alloying process reveals in the improvement of the useful properties of object after electrodischarge alloying.

The paper presents the experimental results on the application laser pulses for evaluation of the surface layer integrity of materials and thin films. Short10 ns, strong 0.5-1.2 J pulses have been used to induce a stress wave in the tested materials. The stress wave induced plastic deformation of the surface of the tested materials and delamination of thin films. The hardness test was elaborated at a strain rate of 107 s-1. The method was used to evaluate dynamic hardness of typical materials. The achieved results showed good repeatability of the measured values, and the developed method proved to be sensitive to even small changes in the properties of the tested materials. The residual stresses of thin films using the LST (Laser Spallation Technique) method were also analyzed at work. The tests were carried out for PVD films on steel substrate. Based on the geometry of the separated film, the residual stresses in films can be determined with high accuracy. The residual stress value obtained by the LST method was consisted with XRD method.

The interaction of laser beam with dissimilar metals during welding process was studied theoretically. A finite element based three-dimensional transient heat transfer and fluid flow model was applied for prediction temperature distribution and material mixing field as well as weld dimensions. The model was used for study and optimization process parameters of welding of Ni – Pt spark plug for bio-fuel engine. The laser pulse duration and energy, and the angle of incidence of the laser beam to thesurface were analyzed. The shape of the melting pool obtained from the theoretical model was close to experimental results.

Inexpensive Tungsten Tetraboride super hard coatings prepared by pulsed laser deposition (PLD) method are investigated. WB4 coatings were prepared on Si (100), by PLD technique using nanosecond, Nd:YAG laser operating at 355 nm wavelenght. Additionally the surface of SPS sintered WBx target before and after ablation process was examined. Phase change of WB2 to WB4 at the surface of target is observed. The phase analysis, crystallography and orientations have been studied using X-ray diffractometry. The surface layer of target after ablation and deposited films are found to be mostly WB4 phase with hardness HV>28 GPa.

laser mikro/nano engineering, thin films, pulsed laser ablation/deposition, tungsten tetraboride WB4