A high power direct diode laser, emitting in the range of near infrared radiation at wavelength 808-940 nm, was applied to produce a titanium matrix composite on a surface layer of titanium alloy Ti6Al4V by laser surface gas nitriding. The nitrided surface layers were produced as single stringer beads at different heat inputs, different scanning speeds, and different powers of laser beam. The influence of laser nitriding parameters on the quality, shape, and morphology of the surface layers was investigated. It was found that the nitrided surface layers consist of titanium nitride precipitations mainly in the form of dendrites embedded in the titanium alloy matrix. The titanium nitrides are produced as a result of the reaction between molten Ti and gaseous nitrogen. Solidification and subsequent growth of the TiN dendrites takes place to a large extent at the interface of the molten Ti and the nitrogen gas atmosphere. The direction of TiN dendrites growth is perpendicular to the surface of molten Ti. The roughness of the surface layers depends strongly on the heat input of laser nitriding and can be precisely controlled. In spite of high microhardness up to 2400 HV0.2, the surface layers are crack free.
Abstract. The state of laser processing in surface materials modification in Poland is reported, based on own experience, coworkers and coauthors results, as well the literature review. The curriculum concerning historical development of lasers and laser technology in Poland, laser-matter interaction, as well basis of different laser techniques applied in materials surface engineering (solid state hardening, melting, alloying, cladding, ablation, shot peening, cleaning and texturing) are reviewed, and compared with results of coauthors, as well with a wide range of Polish authors papers. Finally, it is concluded that overall state of research on laser application in surface engineering in Poland is well developed and still growing industrial application is observed.
The autogenous laser welding of 2.5 mm thick butt joints of thermomechanically rolled fine-grain steel grade S420MC was investigated. Butt joints were laser welded by the Yb:YAG Disk laser, emitted a circular laser beam with spot diameter of 200 µm at 1.03 µm wavelength, and also by the high power direct diode laser, emitted a rectangular beam with dimension of 1.8×6.8 mm at 808 nm wavelength. Different welding modes were identified for the lasers applied. The conduction welding mode was observed in whole of the diode laser welding parameters. While high quality joints, without any internal defects and characterized with satisfactory mechanical performance were produced in a wide range of parameters. The butt joints produced by Disk laser were welded at keyhole mode. In this case a slight tendency to weld porosity was found.Keywords: laser, welding, keyhole, thermomechanically rolled, fine-grain steel W artykule przedstawiono wyniki badań procesu spawania laserowego bez materiału dodatkowego złączy doczołowych ze stali drobnoziarnistej walcowanej termomechanicznie S420MC. Złącza doczołowe spawano laserowe za pomocą lasera dyskowego Yb:YAG, który emituje wiązkę laserową o przekroju kołowym i średnicy ogniska 200 µm przy długości fali promieniowania laserowego 1.03 µm, jak również za pomocą lasera diodowego dużej mocy o prostokątnym kształcie ogniska i długości fali 808 nm. Badania wykazały, że mechanizmy i techniki spawania zastosowanymi laserami są odmienne. W przypadku lasera diodowego w całym zakresie parametrów spawanie odbywało się z utworzeniem jeziorka spoiny. Złącza próbne spawane w szerokim zakresie parametrów charakteryzowały się wysoką jakością, brakiem wad wewnętrznych i wysokimi właściwościami mechanicznymi. Z kolei zastosowanie lasera dyskowego spowodowało, że złącza doczołowe były spawane z utworzeniem kanału parowego, tzw. oczka spoiny. W tym przypadku stwierdzono jednak nieznaczną skłonność do porowatości spoin.
The paper provides an analysis of the reasons for excessive wear of the camshafts system components based on models developed to describe the impact of selected material, technological and operational factors. The subject of the research was wear of camshaft cams studied in accordance with results of operation tests. Based on the said tests, the dependence of wear intensity of cams from their angular position was established. The respective calculation results enabled the function of cam fallibility to be determined.Keywords: metallographic structure, wearing, friction W artykule przedstawiono analizę przyczyn nadmiernego zużycia elementów układu rozrządu w oparciu o modele opracowane w celu opisania wpływu wybranego materiału, czynników technologicznych i operacyjnych. Przedmiotem badań było zużycie krzywek wałka rozrządu badanych zgodnie z wynikami badań eksploatacyjnych. Na podstawie tych prób ustalono zależność intensywności zużywania krzywki od ich położenia kątowego. Wyniki obliczeń pozwoliły wyznaczyć funkcję zużycia krzywki.
The article presents results of investigations on autogenous laser welding of new grade STRENX 1100 MC steel. The modern Disk laser was applied for of 5.0 mm thick butt joints welding. The influence of laser welding parameters, mainly the energy input of laser welding on the penetration shape, weld quality, structure and mechanical performance was investigated. It was found that the investigated steel has surprisingly low carbon equivalent CET just 0.328, and also relatively high temperature of martensitic transformation M s at 430.6°C. Despite very rapid cooling times t 8/5 in a range from 0.6 to 1.3 s, thus rapid solidification there was no tendency to cracking of weld metal or HAZ. Significant drop of microhardness in the HAZ resulted in a decrease of tensile strength of joints, compared to the base metal. Impact toughness of test joints was at only 50÷60% of the base metal.
The article presents the results of investigations on autogenous laser welding of the new-generation advanced high-strength steels (AHSS) Domex 960, classified as thermomechanically rolled steel by the manufacturer. There is little information about welding this steel grade, relating only to arc-welding methods. Therefore, a modern disk laser was used for the butt-joint welding of 5.0 mm steel sheets. The results of a microstructure study, tensile tests, technological bending tests, impact-toughness tests and also microhardness measurements showed that a low heat input during the laser welding of the new Domex 960 grade steel is advantageous. A low heat input and thus a high cooling rate of the weld metal and the heat-affected zone (HAZ) led to the formation of a favourable fine-grained microstructure, providing also high mechanical properties of butt joints, comparable to the properties of the base metal. Despite the high cooling rates, there was no significant increase in the microhardness measured across the butt joints. Moreover, a slight decrease in the microhardness was observed in the HAZ. Keywords: laserlaser welding, disk laser, thermomechanically rolled steel, advanced high-strength steel, fine-grained steel, properties of welded jointŝ lanek predstavlja rezultate preiskav avtogenega laserskega varjenja nove generacije naprednih visokotrdnostnih jekel (AHSS), jekla Domex 960, ki so ga proizvajalci opredeljujejo kot termomehansko valjano jeklo. Malo je informacij o varjenju te vrste jekla, nekaj le za metode oblo~nega varjenja. Za sole`no varjenje 5 mm debelih plo~evin je bil uporabljen modern diskasti laser. Rezultati {tudija mikrostrukture, nateznih preizkusov, tehnolo{kih upogibnih preizkusov, preizkusov udarne`ilavosti in tudi meritev mikrotrdote, so pokazali, da je ugoden majhen vnos toplote med laserskim varjenjem nove vrste jekla Domex 960. Majhen vnos toplote in zato velika hitrost ohlajanja kovine v zvaru in v toplotno vplivani coni (HAZ), povzro~i nastanek`eljene drobno zrnate mikrostrukture in tudi zagotavlja visoke mehanske lastnosti sole`nega zvara, v primerjavi z lastnostmi osnovne kovine. Kljub velikim hitrostim ohlajanja, ni bilo ob~utnega pove~anja mikrotrdote, izmerjene preko sole`nega zvara. Poleg tega je bilo v HAZ opa`eno rahlo zmanj{anje mikrotrdote. Klju~ne besede: lasersko varjenje, diskasti laser, termomehansko valjano jeklo, napredna visokotrdnostna jekla, drobno zrnato jeklo, lastnosti zvarjenih spojev
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