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Povzetek: AISI H13 is commonly used for tooling, where higher wear resistance, thermal fatigue resistance, or hot toughness is required. Such examples include forging dies, plastic molds, hot shear blades, high-pressure die casting, and extrusion dies. Thus, thermal conductivity is one of the most important factors for hot work tools. Typically, the work cycle of a hot work tool designed for forging consists of four main phases: the forging stroke, with which the die imparts its shape onto the part, a brief pause while the die is reset to its original position, a lubrication phase, and a post lubrication dwell phase. During the forging phase, a significant amount of heat is transferred to the die while it is in contact with the part. This heat must then be dispelled for the part to return to a working temperature. While somewhat different, other hot work processes mentioned above are similar in that the hot work tool gets heated to a high temperature due to the contact with the object of deformation. The process of additive manufacturing (AM) promises better, more efficient tool production with features like conforming cooling channels, which would reduce the thermal fatigue of tools, prolonging tool life. However, the powder bed fusion (PBF) method creates a columnar microstructure, which has a detrimental effect on the thermal conductivity of H13 tool steel. Our investigation focused on the beneficial effect of heat treatment, specifically annealing at different temperatures, on the thermal conductivity of AM-produced H13 parts.
Ključne besede: SLM, thermal conductivity, tool steel, heat treatment
Objavljeno v DiRROS: 28.02.2024; Ogledov: 202; Prenosov: 86
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Ključne besede: aluminium alloy, heat treatment, microstructure, dispersoids, dilatometry, DSC, hardness
Objavljeno v DiRROS: 02.02.2024; Ogledov: 305; Prenosov: 116
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Ključne besede: low density steels, heat treatment, tensile test
Objavljeno v DiRROS: 02.02.2024; Ogledov: 236; Prenosov: 98
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Povzetek: In the field of surface treatment, laser colour marking can be used to produce coloured marks on the surfaces of metals. Laser colour markings can be applied to various materials, but on titanium alloys a wide spectra of vivid colours can be achieved. This study presents an analysis of the corrosion properties of laser treated surfaces that were exposed to aggressive environments. Different samples were prepared with laser light of various power intensities and processing speeds. The samples were prepared on low alloyed Ti. Electrochemical, spectroscopic and microstructural analyses were conducted in order to study the properties of the laser treated surfaces. Corrosion testing showed different effects of laser power and production speed on the properties of the laser treated surfaces. It was shown that a high intensity and slow processing rate affect the surfaces by forming oxides that are relatively stable in a corrosive environment of 0.1 M NaCl. Spectroscopic investigations including scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) analyses showed the differences in chemical structure of the surface layer formed after laser treatment. Similarly, microstructural investigations showed different effects on the surface and sub-surface layer of the laser treated samples.
Ključne besede: Ti alloy, laser treatment, XPS, corrosion
Objavljeno v DiRROS: 25.10.2023; Ogledov: 451; Prenosov: 178
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Povzetek: TiO2+Pt plasmonic solids with 1 wt% Pt and different TiO2 supports (anatase nanoparticles (TNP), polycrystalline nanorods (a-TNR) and single-crystal anatase nanorods (TNR)) were synthesized using the wet impregnation technique and tested as photo, thermal and photothermal catalysts in gas-solid and gas-liquid-solid reactions. Due to the different charges of the TiO2 support surfaces, Pt particles with different sizes, crystallinities and degrees of interaction with the TiO2 supports were formed during the synthesis. The heights of the Schottky barrier (SBH) were 0.38 eV for the a-TNR+Pt, 0.41 eV for the TNP+Pt, and 0.50 eV for the TNR+Pt samples, respectively. The low visible-light-triggered photocatalytic activity of the TNR+Pt catalyst toward the oxidation of water-dissolved bisphenol A (BPA) is attributed to its high SBH and active site deactivation due to the adsorption of BPA and/or BPA oxidation products. The highest photothermal catalytic H2-assisted NO2 reduction rate was expressed by the TNR+Pt catalyst. This can be ascribed to the presence of a narrow particle size distribution of small Pt particles, the absence of the Pt catalysed reduction of the TNR support at higher temperatures, and the lower rate of re-injection of “hot electrons” from the TNR support to the Pt particles.
Ključne besede: heterogeneous photocatalysis, titanium dioxide, plasmonic noble metal, platinum particles, visible light illumination, Schottky barrier height, bisphenol A, wastewater treatment, NOx abatement, air cleaning, microreactor, thermal catalysis, photothermal catalysis
Objavljeno v DiRROS: 23.06.2023; Ogledov: 435; Prenosov: 239
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