Browsing by Keyword "Hardness"
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Item Hardness, grainsize and porosity formation prediction on the Laser Metal Deposition of AISI 304 stainless steel(2018-12) Arrizubieta, Jon Iñaki; Lamikiz, Aitzol; Cortina, Magdalena; Ukar, Eneko; Alberdi, Amaia; FABRIC_INTELThe presented numerical model solves the heat and mass transfer equations in the Laser Metal Deposition process and based on the evolution of the thermal field predicts the grainsize, the resulting hardness and evaluates the pores formation probability in an AISI 304 stainless steel. For this purpose, in a first step, the model calculates the shape of the deposited material and the variations of the temperature field. In a second step, and based on the evolution of the thermal field, the model calculates the resulting hardness of the deposited material, the grainsize and the porosity formation probability after the deposition process. Numerical results are experimentally validated, and good agreement is obtained. Consequently, besides predicting the geometry of the resulting part and the evolution of the thermal field, the developed model enables to evaluate the quality of the deposited material. Therefore, the optimum process conditions and strategy when depositing AISI 304 stainless steel can be determined without initial trial-and-error tests.Item Magnetron sputtering of Cr(Al)N coatings: Mechanical and tribological study: Mechanical and tribological study(2005-10-01) Brizuela, Marta; García-Luis, A.; Braceras, I.; Onate, J.I.; Sánchez-López, J.C.; Martínez-Martínez, D.; López-Cortés, C.; Fernández, A.; López-Cartes, C.; INGENIERÍA DE SUPERFICIES; TECNOLOGÍAS DE HIDRÓGENO; Tecnalia Research & InnovationCrN coatings produced by magnetron sputtering are routinely deposited on tools and components for machining and forming applications. This paper reports on the effect of additions of aluminium (<15 at.%) on the mechanical and tribological properties of CrN coatings. Aluminium has been incorporated into CrN by co-sputtering of chromium and aluminium in a mixture of argon and nitrogen. Mechanical properties have been evaluated by ultramicroindentation techniques and scratch testing, while tribological tests have been carried out against ball bearing steel and titanium alloy balls by the pin-on-disc method. The thermal stability and oxidation resistance of the coatings have also been examined. A significant increase in hardness, reaching values up to 35 GPa, has been achieved for the CrAlN coatings when compared to CrN coatings. The improvement in tribological properties has also been remarkable, with a decrease in friction coefficient against bearing steel and also a non-adhesive wear mechanism against titanium alloy balls. In addition, the CrAlN coatings exhibited higher thermal stability than pure CrN coatings.Item Mechanical properties of nanocrystalline Ti–B–(N) coatings produced by DC magnetron sputtering(2005-10-01) García-Luis, A.; Brizuela, Marta; Onate, J.I.; Sánchez-López, J.C.; Martínez-Martínez, D.; López-Cartes, C.; Fernández, A.; TECNOLOGÍAS DE HIDRÓGENO; INGENIERÍA DE SUPERFICIES; Tecnalia Research & InnovationTi–B–(N) coatings have been deposited by DC magnetron sputtering using TiB2 targets in Ar/N2 gas mixtures. The influence of bias voltage and nitrogen flow on the mechanical and tribological properties of these coatings has been studied. Mechanical properties have been evaluated by ultra-microindentation techniques and scratch testing; tribology tests have been performed in a pin-on-disc apparatus with controlled humidity conditions. Microstructural characterization by X-ray diffraction (XRD) and Transmission Electron Microscopy (TEM) demonstrates the nanocrystalline structure of Ti–B–(N) coatings and allows the interpretation of their mechanical behaviour. Hardness values up to 58 GPa have been achieved, depending on deposition conditions. Increasing the bias voltage on the substrates improves the hardness of coatings, while the addition of nitrogen significantly decreases these values. Coating adhesion obtained on highspeed steel is very good in most cases, reaching values higher than 60 N of critical load. Tribotests performed on these coatings against a Steel contact (wear conditions: 0.98 N load, 10 cm/s, 50% RH, 10 mm bearing steel ball diameter) have yielded very low wear rates but friction coefficients in the range of 0.6–1.0.Item Microstructural Evolution as a Function of Increasing Aluminum Content in Novel Lightweight Cast Irons(2021-10-18) Obregon, Alejandro; Sanchez, Jon Mikel; Eguizabal, David; Garcia, Jose Carlos; Arruebarrena, Gurutze; Hurtado, Iñaki; Quintana, Ion; Rodriguez, Patxi; PROMETAL; CIRMETALIn the context of the development of new lightweight materials, Al-alloyed cast irons have a great potential for reducing the weight of the different part of the vehicles in the transport industry. The correlation of the amount of Al and its effect in the microstructure of cast irons is not completely well established as it is affected by many factors such as chemical composition, cooling rate, etc. In this work, four novel lightweight cast irons were developed with different amounts of Al (from 0 wt. % to 15 wt. %). The alloys were manufactured by an easily scalable and affordable gravity casting process in an induction furnace, and casted in a resin-bonded sand mold. The microstructural evolution as a function of increasing Al content by different microstructural characterization techniques was studied. The hardness of the cast irons was measured by the Vickers indentation test and correlated with the previously characterized microstructures. In general, the microstructural evolution shows that the perlite content decrease with the increment of wt. % of Al. The opposite occurs with the ferrite content. In the case of graphite, a slight increment occurs with 2 wt. % of Al, but a great decrease occurs until 15 wt. % of Al. The addition of Al promotes the stabilization of ferrite in the studied alloys. The hardness obtained varied from 235 HV and 363 HV in function of the Al content. The addition of Al increases the hardness of the studied cast irons, but not gradually. The alloy with the highest hardness is the alloy containing 7 wt. % Al, which is correlated with the formation of kappa-carbides and finer perlite.