E. Restrepo

Study of W/WC Coatings Varying the Substrate Temperature

Tungsten carbide is considered a very important material used for industrial applications due to their high hardness. In this work the production of W/WC coatings used a repetitive pulsed arc system is employed. During the grown process, the substrate temperature is varied in order to identify the influence of this parameter in the structure, composition and morphology of the coatings. The layer of W is grown to improve the adherence of the WC material on the stainless steel 304. To grown the coatings, it was used a W target in the cathode. The gas of work is methane and as it is knew, to use a gas as precursor for WC production causes the apparition of different phases as WC and W2C. The power supply allows varying the active and passive time of pulses, which in this case have a value of 1 s. the coatings produced are characterized by X‐ray diffraction (XRD), X‐photoelectron spectroscopy (XPS) and scanning probe microscopy (SPM). All of these techniques allow determining properties such as chemical compo...

Structural and Morphological Difference Between Ti/TiN/TiCN Coatings Grown in Multilayer and Graded Form

Thin films can be grown in super‐lattice, multilayers and graded form, having each one advantages and disadvantages. The difference between multilayer and graded coatings is the interface. In multilayers the interface is abrupt and in graded coatings it is diffuse. The interface influences many chemical and physical properties of the materials, and its choice depends on the application. Graded coatings have the advantage of having gradual properties such as thermal expansion coefficient and lattice parameter, avoiding adherence problems due to good match between their component materials. In this work the comparison between some properties of coatings grown as multilayer and graded is performed. The materials are produced using the sputtering DC technique because of its facility to control the deposition parameters and generate a slow growth. The target is a disc of titanium and the samples are made of stainless steel 304. The working gases are argon, nitrogen and methane, which are mixed according to the...

Temperature and density measurements for pulsed plasmas using spectroscopy methods

In this work we show an experimental study of plasmas generated by a pulsed discharge in order to produce hard coatings of TiN. Optical spectroscopy techniques were used to study the emission characteristics of the plasma. A methodology as been applied that relates the intensity of different emission lines, to calculate the excitation temperature. In both cases one must obtain integral over each line profile. The Stark broadening was measured by determining the FWMH of the line profile and subtracting the instrumental broadening, the line shapes obtained show a mostly Lorentzian profile and thus, Doppler broadening may be neglected.

Automated system for identification of atomic elements and calculation of lines profiles in emission spectra

A database was designed starting from the Kurucz cd-rom N0 23 of the Smithsonian Astrophysical Observatory. In this database the different atomic elements are ordered by wavelength with their ionization levels. Also, there are other data like statistic weight, Einstein’s coefficient, information about energy levels, constant of damping, among others. The spectra of the discharge are processed using a digital filtrate technique, with the purpose of reducing the noise present in the data to locate the points where the maximum amplitudes are presented. Starting from these results, consultations dynamic SQL are made, these obtain the elements present in these regions from the database. Finally, by means of the use of statistical methods it is determined which are the elements that have the highest probability of conform with the plasma.

Variation of Plasma Parameters as Function of the Pressure

This work presents measurements of temperature and density of a plasma as function of pressure. The plasma was produced by a pulsed discharge used to obtain TiN coatings. The system is composed by a chamber, which is filled with nitrogen at pressures that vary between 0.2 to 3.0 mb. Optical emission spectra were taken in different regions, and then, twenty lines were used to calculate the temperature using the relation line ‐line method. Moreover, the method of relation between lines of same species and consecutive ionization state is utilized to calculate the density of the plasma.