Structural, hardness and tribological behavior of TiAlNO coatings prepared by sputtering
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of the experimental values to obtain a unique hardness value, eliminating the contribution of 316 steel and obtaining only the real value of the hardness of the coatings. In order to model the 316 steel -coating behavior we used the equation: 𝐻𝑇 = 𝐻𝑠 +
𝐻𝐹 −𝐻𝑠 1+𝑘𝛽 2
(1)
where HF corresponds to the hardness of the coating, Hs.- the hardness of the 316 steel substrate, HT.- total hardness of the steel – coating system, .- the relative indentation depth k.- is a dimensionless material parameter Using a tribometer Pin on disc (ASTM G-99), we then proceeded to assess wear resistance of the TiAlNO coatings. The method constitutes mounting a pin in a perpendicular manner pin a disc. The pin is pressed onto the disc, which moves according to a specific load and as a result, a track is formed on the disk. The amount of wear is established by weighing the pin and the disc with a microbalance before and after the test. Induced mass loss by wear can be converted into volume loss using appropriate density values. Thus, reports of wear are made in terms of volume loss in cubic millimeters. Two types of procedures are used for performing these assays: coated circular discs with a diameter of 29.15 mm and thickness of 3.32 mm and uncoated cylindrical pins with diameter of 6.28 mm and length of 35 mm. The conditions for the tests were Pair tribological Pin-Disc, load average 30 N, velocity 300 rpm and time of 10 min. There were four replicas for each coating, in order to evaluate the influence of the variation in nitrogen flow with respect to wear resistance. RESULTS AND DISCUSSION Structural properties Figure 1 a) illustrates the X-ray diffractograms of all coatings fabricated by the sputtering technique. In these diffraction peaks we can identify three crystalline phases using the PDF (Powder Diffraction File) of ICDD (International Centre Diffraction Data) titanium nitride (Ti2N) with ICDD: 01-077-1893, titanium oxide (TiO2) with rutile structure with ICDD: 00003-1122 and aluminum oxide (Al2O3) with ICDD: 00-023-1009. The Ti2N phase has identified peaks in 2θ=36.808°, 43.591° y 74.276°, with a crystalline structure body-centered tetragonal with an orientation in plane (112) for coating TiAlNO1 and crystallographic preferred orientation to the other three coatings on the plane (200); the Al2O3 phase has identified peaks at 2θ = 50.680° y 62.339°, with a monoclinic base-centered structure and changing crystallographic orientation for the first two coatings of (113) to (510) for TiAlNO3 and TiAlNO4 and finally the TiO2 phase has a tetragonal structure at 2=44.142° with crystallographic orientation in the plane 210 Subsequently, the presence of a diffraction peak in 2=81.986° is related to the 316 stainless steel. The increasing the nitrogen flow tend to move to the right with respect to the reference lines of the phases Ti2N and TiO2, indicating the existence of compressive stresses due to an increase in the interatomic space material growth in the direction (200). In the case of phase Al2O3, shift is not observed in the
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