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EN
The article presents research on solid particle erosive wear resistance of ductile cast iron after laser surface melting. This surface treatment technology enables improvement of wear resistance of ductile cast iron surface. For the test ductile cast iron EN GJS-350-22 surface was processed by high power diode laser HPDL Rofin Sinar DL020. For the research single pass and multi pass laser melted surface layers were made. The macrostructure and microstructure of multi pass surface layers were analysed. The Vickers microhardness tests were proceeded for single pass and multi pass surface layers. The solid particle erosive test according to standard ASTM G76 – 04 with 30°, 60° and 90° impact angle was made for each multi pass surface layer. As a reference material in erosive test, base material EN GJS-350-22 was used. After the erosive test, worn surfaces observations were carried out on the Scanning Electron Microscope. Laser surface melting process of tested ductile cast iron resulted in maximum 3.7 times hardness increase caused by microstructure change. This caused the increase of erosive resistance in comparison to the base material.
2
Content available remote The role of powder layer thickness on the quality of SLM printed parts
EN
Achieving good mechanical properties as well as the dimensional accuracy and the smooth surface quality of selective laser melting printed parts with minimal post treatments are essential in additive manufacturing. In the present study, Inconel 718 samples with different powder layer thickness (20, 30, 40 and 50 μm) were additively fabricated using 3D Systems ProX-300 machine. The results reveal that the lower the layer thickness, the denser and good dimensional accuracy were achieved. Marginally higher mechanical properties and microhardness were also obtained at the lower thickness while the failure strain was still high. This can be explained through significant change in the microstructure due to different cooling rate and thermal cycles. In addition, the formation of ɤ′ and ɤ″ intermetallic phases, which were well distributed in the matrix and grain boundaries, during heating/cooling, gave rise in the strengths. Fractography shows the plastic deformation band due to work hardening and the crack initiation sites at sub-micro/micro pores, lack of fusion areas and the boundary of unmelted particles. The study would guide engineers balance their options between the production rate and the building parts’ quality.
3
Content available remote Development of WC-Inconel composites using selective laser melting
EN
In the present study, selective laser melting (SLM) was used to successfully fabricate Inconel 718–tungsten carbide (WC) composites. The processing parameter optimization results reveal that nearly non-porous composites (99.54%) were achieved with the laser power of 220 W, scanning speed of 850 mm s−1, and the hatch spacing of 150 μm. The microstructural characterization unveils that elongated grain structure in the heat flow direction was observed in the case of pure IN718 while WC particles served as obstacles to hinder the grain growth in the composites. The formation of in situ intermediate layer and the strong interfacial bonding between WC super-hard particles and the matrix acted as load bearing and significantly contribute to the overall properties of composites. Mechanical tests indicate significant improvements of microhardness and tensile strengths, although a drop in strength was observed when the amount of WC reached 15 wt.%. In addition, the thermal experiment shows that the composites are dimensionally stable at higher temperature compared to their monolithic counterpart. The findings suggest that the developed IN718-WC composites can be utilized in many critical engineering applications in nuclear sector.
EN
The fabrication of the prosthetic foundations and bridges from the Ti-13Zr-13Nb alloy is described. The process was started from CAD/CAM design of 3D models of the foundations based on scanning of patient’s mouth. Next, 3D models were transformed into *.stl files for the manufacturing stage and then the manufacturing process by means of the selective laser melting with the SLM Realizer 100 equipment was made. The intrinsic structure of the obtained parts was investigated with X-ray microtomography. The observed imperfections in the foundation's internal structure can be eliminated by a proper setting of the laser melting process. The thermal stresses, which resulted of the temperature change during melting and caused the bending of titanium made bridges, were eliminated at a design stage.
EN
Industrial tomography (XCT) is a nondestructive test method that provides information about spatial distribution of X-ray absorption in the analyzed structures. The aim of this paper was to examine the possibility and accuracy of application of XCT method for discontinuity and porosity detection in parts made of 316L stainless steel powder produced by Selective Laser Melting technology. Analysis conducted on three produced test samples showed that the application of XCT as a method of quality control of specimens produced with an additive manufacturing technology offers a wide range of possibilities to detect porosity within materials. Parameters such as the amount of porosity, pore size and pore shape are presented. Accuracy of XCT method strongly depends on the size of the samples analyzed, but the possibility of obtaining information in 3D nondestructively shows considerable advantages of XCT method over traditional metallographic cross-sectional analysis.
6
Content available remote Structure and properties of the laser alloyed 32CrMoV12-28 with ceramic powder
EN
Purpose: The work was performed for the reason to determine the laser treatment parameters, particularly the laser power, to achieve a high value of layer hardness for protection of this hot work tool steel from losing their work stability and to make the tool surface more resistant for work. The purpose of this work was also to determine technological and technical conditions for remelting the surface layer with HPDL. Design/methodology/approach: The main methodology results of new laser treatment techniques applied in metal surface technology are presented and discussed. There is presented laser treatment with remelting of hot work tool steel 32CrMoV12-28 with ceramic powders especially carbide - TaC, as well as results of laser remelting influence on structure and properties of the surface of the hot work steel, carried out using the high power diode laser (HPDL). Special attention was devoted to monitoring of the layer morphology of the investigated material and on the particle occurred. Optical and scanning electron microscopy was used to characterize the microstructure and intermetallic phases occurred. Findings: There was achieved a layer without cracks and defects as well as has a considerably higher hardness value compared to the non remelted material. The hardness value increases according to the laser power used so that the highest power applied gives to highest hardness value in the remelted layer. Research limitations/implications: There were four choused laser powers used and implicated by one process speed rate. Also one powder in form of TaC was used for alloying with the particle size of 10 ěm. Practical implications: This work helps to use the laser treatment technique for alloying and remelting of hot work tool steel. Originality/value: The originality of this work is based on applying of High Power Diode Laser for improvement of steel mechanical properties.
EN
Purpose: In this work are presented the performed investigation for the reason to determine the laser treatment parameters, for example the laser power to achieve a high value of layer hardness for protection of this hot work tool steel from losing their work stability and to make the tool surface more resistant for work. The purpose of this work was also to determine technological conditions for remelting the surface layer with HPDL. Design/methodology/approach: The research way results of new laser treatment methodology applied in metal surface technology are presented and discussed. There is presented laser treatment with remelting of hot work tool steel 32CrMoV 12-28 with ceramic powders especially titanium carbide - TiC, as well as results of laser remelting influence on structure and properties of the surface of the hot work steel, carried out using the high power diode laser (HPDL). Special attention was devoted to monitoring of the layer morphology of the investigated material and on the particle occurred. Optical and scanning electron microscopy was used to characterize the microstructure and intermetallic phases occurred. Findings: A surface layer was comming into existence without cracks and defects as well as has a considerably higher hardness value compared to the non remelted material. The hardness value increases according to the laser power used so that the highest power applied gives to highest hardness value in the remelted layer. Research limitations/implications: Four laser powers were choused and implicated by one process speed rate. Also one powder in form of TiC was used for alloying with the particle size of 10 micrometres. Practical implications: The investigation helps to use the laser treatment technique for alloying of hot work tool steel with different ceramic particles. Originality/value: The scientific reason of this work is the applying of High Power Diode Laser (HPDL) for improvement of steel mechanical properties, especially the surface.
PL
Laserowa obróbka impulsowa jest przeznaczona dla obróbki lokalnych miejsc części, które przenoszą znaczne naprężenia kontaktowe. Obszar obróbki ma złożoną budowę zarówno w głębi, jak i na samej powierzchni. Metodą różnic skończonych opracowano model procesu nagrzewania i topienia impulsem laserowym. Wyznaczono parametry geometryczne przestrzeni topienia i wpływu ciepła, gradienty temperaturowe w fazie stałej i płynnej w okresie nagrzewania oraz naturalnego ochładzania. Przeprowadzono próby porównawcze zużycia podczas frettingu różnych fragmentów przestrzeni obróbki stali konstrukcyjnej z dodatkami stopowymi Cr, Mo, W, Nb w czasie działania jednorazowego impulsu.
9
Content available remote Laserowe utwardzanie powierzchni tytanu z wykorzystaniem syntezy TiC.
PL
W pracy przedstawiono metodę utwardzania powierzchni tytanu wytwarzając węglik TiC w warstwie wierzchniej metalu. Węglik wytworzono stapiając warstwę wierzchnią tytanu wiązką laserową w obecności wcześniej osadzonej warstwy koloidalnego grafitu. Badania dotyczyły morfologii powierzchni, składu chemicznego i fazowego powstałych przetopów oraz ich mikrostruktury i mikrotwardości. Morfologia powierzchni po obróbce laserowej była różna w zależności od użytej gęstości mocy wiązki oraz stopnia nakładania się sąsiednich przetopów. Częściowo zachodzące na siebie lokalne przetopy tworzyły ścieżki, w których stwierdzono metodą rentgenograficzną obecność krystalitów faz alfa-Ti oraz delta-TiC. Twardą fazę węglikową o wyraźnej strukturze dendrytycznej obserwowano w całym przetopie. Kierunki dendrytów w pobliżu powierzchni są do niej prostopadłe, co wynika z nierównowagowej, szybkiej krystalizacji fazy delta-TiC w warunkach występującego jednokierunkowego gradientu temperatury. Ilość fazy węglikowej zależała od gęstości mocy promieniowania oraz stopnia nakładania sąsiednich ścieżek i lokalnych przetopów. Na zgładach poprzecznych oprócz tytanu i węgla stwierdzono również obecność tlenu. Mikrotwardości zmierzone na przekrojach poprzecznych zawierały się w granicach 150 HV0.01-1000 HV0.01. Rozkłady mikrotwardości charakteryzują się dużą niejednorodnością, która wynika z intensywnego mieszania i szybkiego stygnięcia cieczy.
EN
A method of titanium surface hardening is presented in the paper in which a hard carbide delta-TiC phase is being created in the vicinity of the titanium surface. The creation of the carbide phase is due to laser melting of the titanium surface previously coated with a thin layer of a colloidal graphite. The experimental conditions as well as the parameters of the pulse laser beam are given. The morphology of the laser treated titanium surface, chemical and phase composition of the melted zone beneath the titanium surface as well as the microstructure and microhardness of the zone have been analysed. The titanium surface after laser treatment has been observed with use of optical microscopy. Surface morphology was changing with power density of the laser beam and with superposition of the adjacent melted zones. The zones were forming long path in which two phases alpha-Ti and delta-TiC have been disclosed by means of X-ray diffractometry. The chemical composition of the melted zones has been performed on the cross sections by means of the electron probe microanalysis. The zones were composed mostly of titanium and carbon atoms, however some amounts of oxygen from the surrounding atmosphere has been detected as well. The hard carbide phase with a dendritic morphology has been observed in far and wide of the melted zones. The directions of the dendrites' axes in the vicinity of the titanium surface are nearly perpendicular to the surface. That phenomenon is due to the solidification of the molten pool under the circumstances of an unidirectional thermal gradient created in result of the laser treatment of the surface. The volume fraction of the carbide phase in the melted zone was changing depending on the superposition of the adjacent zones or paths. The microhardness on the cross sections was changing very irregularly. Its values measured on the section along two straight lines perpendicular to the titanium surface are given. That irregularity is due to a rather intensive stirring in the molten pool succeeded by a very rapid solidification.
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