Papers by Keyword: Laser Beam

Abstract: Amorphous alloys are promising structural materials because of their high mechanical strength. Their drawbacks are low ductility and severe size restrictions for components obtained by casting. Additive manufacturing by selective laser melting (SLM) consists in successive fusion of small portions of material to add to a growing part. Each portion is subjected to a short thermal cycle favorable for amorphization. Thus, one can build an amorphous part as large as necessary. We study the microstructure of cast samples of a zirconium-based bulk metallic glass after laser processing with the parameters typical for SLM. Scanning electronic microscopy has shown partial crystallization in the heat affected zone of the laser beam. The spatial distribution and the volume fraction of the crystalline phase can be controlled by laser processing parameters. The obtained amorphous-crystalline structures are promising to increase the ductility of bulk metallic glasses.

Abstract: The article examines the hardness of the coating made of PG-CP4 powder. Plasma powder deposition was performed to samples made of 40H13 steel and then the samples treated with a laser beam. A multi-factor model was established that relates the hardness of the protective coating to the radiation power W, the longitudinal feed Spr of the laser beam, and the distance L from the protective casing of the laser head to the treated surface. Depending on the laser treatment modes, coating was in a state of complete, partial reflow or its absence. Full reflow is characterized by the adhesion of the filler material to the substrate, by maximum hardness of HRC 51.2–56.6 and no defects. In the absence of reflow, gas sinks, transverse microcracks, detachments, and other defects were found in the coating material, and the hardness decreased to HB 125–212. An increase in W and a decrease in Spr lead to increases the hardness of the treated coating, which is explained by an increase in the specific heat flux supplied to the coating per unit time, and a high rate of heat removal deep into the surface layer of 40H13 steel. The thickness of the surface layer with increased hardness ranged from 0.1 to 1.5 mm. Based on the multi-factor model, laser processing modes are controlled to ensure the required values of the protective coating hardness. The research results are recommended for use in enterprises that implement laser technologies and develop modern laser systems.

Abstract: Study of weld joints of nonferrous, Inconel 625 alloy sheets using a new generation disk laser as the green welding technology for the effective manufacturing were carried out, and the results are presented in this paper. Weld joints of the Inconel 625 alloy sheets 2,0 mm thick were welded by laser without an additional material at a flat position, using a high purity argon as the shielding gas. The influence of laser welding parameters on weld quality and mechanical properties of test joints was studied. The influence of welding speed and laser power to the joint quality was investigated. The study of quality and mechanical properties of the joints were determined by metallographic evaluation, tensile and hardness tests.

Abstract: The paper presents the investigation results of a metal plate re-melting process by a fiber laser beam using a high-speed video camera. The obtained video materials allow observing the transition process of molten metal to a solid state. The dependence of the molten metal transition to the solid state on the laser welding speed and on the focal distance (in the range of ± 20 mm) is analyzed. A quantitative analysis of the geometric dimensions of the microstructural components of the re-melted metal was carried out. When comparing the processed video material and microstructure elements of the molten pool, the similar trends are observed depending on the re-melting speed by a laser beam in a certain range of speeds from 20 to 45 mm/s. The obtained results can be used to develop a technique for estimating the presence of a key-hole depending on the laser focal distance.

Abstract: Steam turbine blades in the process of operation are subjects on which the high mechanical loads, erosion, corrosive and vibration effects. These factors significantly reduce their service life, which forces to costly repair work. The application of heat and wear-resistant coating on the turbine blades is a rational way to increase the service life of the turbine.

Abstract: Selective Laser Sintering (SLS) is an HYPERLINK "https://en.wikipedia.org/wiki/Additive_manufacturing" \o "Additive manufacturing" additive manufacturing (AM) technique that uses a HYPERLINK "https://en.wikipedia.org/wiki/Laser" \o "Laser" Laser as the power source to HYPERLINK "https://en.wikipedia.org/wiki/Sintering" \o "Sintering" sinter powdered material, typically HYPERLINK "https://en.wikipedia.org/wiki/Nylon" \o "Nylon" nylon/ HYPERLINK "https://en.wikipedia.org/wiki/Polyamide" \o "Polyamide" polyamide HYPERLINK "https://en.wikipedia.org/wiki/Selective_laser_sintering" \l "cite_note-1" [7], HYPERLINK "https://en.wikipedia.org/wiki/Selective_laser_sintering" \l "cite_note-2" [8]. A Laser beam HYPERLINK "https://en.wikipedia.org/wiki/Automation" \o "Automation" automatically aims at points in space defined by a HYPERLINK "https://en.wikipedia.org/wiki/3D_modeling" \o "3D modeling" 3D model, binding the material together to create a solid structure. In the SLS rapid prototype machine, a high power CO₂ Laser sources is applied for sintering the powder material to its melting point temperature. The ability of application of a Laser radiation for sintering the material depends on the power of energy source and the time of interaction of radiation with the material of the product. Otherwise, the design of Laser beam for sintering powder material depends on the technical parameters such as power Laser source, Laser point size, type and focus of lenses.... This article presents a study on the design of our own Laser beam sintering in the SLS rapid prototype that satisfies the technical requirements. The results of testing show that the designed and manufactured Laser beam instrument in SLS rapid prototype machine in our laboratory can be approved because it satisfies all the technological requirements of the medium range of SLS rapid prototyping machine.

Abstract: Electron beam (EBAM) and laser beam (LBAM) additive manufacturing processes with a deposited material in the form of a wire are an efficient methods enabling the making of component parts. The scope of the presented work was to investigate the influence of technological process on microstructure and mechanical properties such as tensile strength, microhardness and elongation of the fabricated components. The achieved results and gained knowledge will enable the production of a whole structure from stainless steel in the future. The metallographic examination revealed that the microstructure is not fully homogenies, the cell-dendritic areas occurred. Moreover, the microhardness profiles indicated that some fluctuation in the microstructure as well as mechanical properties can be observed on the cross section of deposited components. However, the mechanical tests showed that the tensile strength as well as elongation fulfil the requirement of producer of deposited wire.

Abstract: It is well-known that a series of cracks sometimes gets initiated perpendicular to the cutting edges on the rake faces of brittle cutting tools made of materials such as cemented carbide, ceramics, and cermet under high-speed intermittent cutting. The tools used in intermittent cutting processes are exposed to elevated temperatures during cutting and then cool quickly during the noncutting time. Previous studies have suggested that such repeated thermal shocks generate thermal stress in the tool and that the thermal cracks are then propagated by thermal fatigue. Recently, high-speed machining techniques have attracted the attention of researchers. To apply new cutting tool materials to this machining process, it is important to evaluate their thermal shock fatigue resistances. During high-speed intermittent cutting, the frequency of thermal shocks becomes high and the action area of the thermal shocks is limited to the rake face of the tool. Therefore, conventional thermal shock resistance evaluation methods are unsuitable for this case. Consequently, the authors have developed a new experimental evaluation method using a CO₂ laser beam. In this study, we irradiated cemented carbide and TiN cermet cutting tools with the CO₂ pulse laser beam and gauged the effectiveness of the proposed thermal shock fatigue resistance evaluation method. The results show a correlation between the thermal shock due to the CO₂ pulse laser beam and those due to the intermittent cutting experiments.

Abstract: During of aluminum alloy materials, it is possible to find three surface types which can be distinguish as primary, secondary and tertiary sections. In practice this is a big problem in case of finding the basic parameters of roughness and waviness as described by ISO 4288. According to our research, it is possible to use optical microscopy in the first step and subsequently to scan the surface in 3D in order to distinguish the type of. Another problem is how to determine the boundaries between the individual structures. The article describes methods to distinguish the boundaries in a more precise way by the cumulative functions, leading to more accurate determination of the surface quality parameters.

Abstract: When laser beam is effected on the material, the surface properties of material can be damaged, and the damage effect is different for the different laser beams. Nevertheless, the distribution of laser intensity is influenced by the proportion of high-frequency phase in wavefront. By researching the propagation character of wavefront phase, the relation of high-frequency phase and laser intensity is given in this paper. The results show that the focal spot increases gradually with the increase of the proportion of high-frequency phase, the peak value of intensity decreases obviously, and the number of side lobe increases observably.