Ferhat Bülbül

The effects of deposition parameters on surface morphology and crystallographic orientation of electroless Ni-B coatings

Electroless Ni-B coatings were deposited on AISI 304 stainless steels by electroless deposition method, which was performed for nine different test conditions at various levels of temperature, concentration of NaBH4, concentration of NiCl2, and time, using the Taguchi L9(34) experimental method. The effects of deposition parameters on the crystallographic orientation of electroless Ni-B coatings were investigated using SEM and XRD equipment. SEM analysis revealed that the Ni-B coatings developed six types (pea-like, maize-like, primary nodular, blackberry-like or grapes-like, broccoli-like, and cauliflower-like) of morphological structures depending on the deposition parameters. XRD results also showed that these structures exhibited different levels of amorphous character. The concentration of NaBH4 had the most dominant effect on the morphological and crystallographic development of electroless Ni-B coatings.

Investigation of structural and tribological properties of electroless Ni–B coated pure titanium

In the present study, the surface of commercial pure (Grade 2) titanium was coated with electroless Ni–B and, then, it was subjected to heat treatment for an hour at 400 ℃. The surface morphology, microstructure and phase identification were analysed by X-ray diffraction and scanning electron microscope. Wear behaviour characterisation was carried out using a ball-on-disc tribometer. The results of the analyses showed that the electroless Ni–B coating had a significantly amorphous structure in the as-deposited condition. It was also determined that the coating structure crystallised after the heat treatment and wear resistance of pure titanium increased after electroless Ni–B coating. Particularly, upon the heat treatment, it was observed that wear resistance and surface hardness of pure titanium considerably increased.

Preparation and characterization of electroless Ni–B/nano-SiO2, Al2O3, TiO2 and CuO composite coatings

Ni–B/SiO2, Al2O3, TiO2 and CuO composite coatings were successfully obtained by the electroless plating technique. Dispersible SiO2, Al2O3, TiO2 and CuO nanoparticles were co-deposited with electroless Ni–B coating onto AISI-304 steel substrates. Deposits were characterized for its structural properties by X-ray diffraction (XRD). XRD results showed a broad peak of Ni–B and low intensity composite nanoparticle peaks. The surface and cross-section morphology of samples were analysed using a scanning electron microscope (SEM). Surface analysis showed that the incorporation in Ni–B matrix of nano-SiO2, Al2O3, TiO2 and CuO particles increases the nodularity of composite coatings. The deposits are composed of a columnar structure grown along the vertical direction of the substrate surface. The results also show that electroless nanocomposite coatings tend to have greater microhardness compared with the coating without nanoparticles. The increase in the microhardness of the nanocomposite coatings reported in this study is attributed to an effect of dispersion strengthening of ceramic particles in the Ni–B matrix.

Investigation of structural, tribological and corrosion properties of electroless Ni–B coating deposited on 316L stainless steel

The AISI 316L type of stainless steel is a popular steel material, as it has excellent corrosion resistance in aqueous solutions at ambient temperatures. However, the application of the AISI 316L stainless steel is limited by its relatively low hardness and low wear resistance. In this study, the electroless Ni–B coating was deposited on the AISI 316L stainless steel, and its structural, tribological and corrosion properties were characterised. Microstructural analysis showed that the electroless Ni–B coating deposited on the AISI 316L steel substrate exhibited a typical cauliflower-like structure exhibits an amorphous growth. From this study, it may be concluded that this process cannot only improve the hardness and wear resistance of the 316L stainless steel, but can also provide cathodic protection without losing or sacrificing the original properties of the 316L stainless steel.

Tribological and corrosion behaviour of electroless Ni-B coating possessing a blackberry like structure

This study aims to evaluate the tribological and corrosion properties of the electroless Ni-B coating deposited on AISI 304 stainless steels. The microstructure of the coating was characterized using x-ray diffraction (XRD) and scanning electron microscopy-energy dispersive spectrometry (SEM-EDS). XRD analysis revealed that the prepared coating possessed an amorphous character. SEM-EDS investigation also indicated that a non-stoichiometric Ni-B coating was deposited with a columnar growth mechanism on the stainless steel substrate and the morphology of the growth surface was blackberry-like. The hardness and tribological properties were characterized by microhardness and a pin-on-disc wear test. The electroless Ni-B coated sample had a higher degree of hardness, a lower friction coefficient and a lower wear rate than the uncoated substrate. The electrochemical potentiodynamic polarization method was used to evaluate the corrosion resistance of the coating. The electroless Ni-B coating offered cathodic protection on the substrate by acting as a sacrificial anode although it was electrochemically more reactive than the stainless steel substrate.

MoS2-Ti composite films having (002) orientation and low Ti content

MoS2 is a solid lubricant exhibiting the properties like graphite as structure. The selection and control of deposition parameters should be attached importance very much since it exposes the properties desired from tribological and mechanical directions. Its usage is limited at atmospheric conditions because it is very sensitive to humidity. Therefore, both mechanical strength and resistant to oxidation can be provided by adding a suitable selected interleaving metal into MoS2 matrix and by using suitable deposition parameters. In this work, MoS2-Ti, composite films were grown on AISI 52100 steel by PMS (pulsed magnetron sputtering), and evaluated mechanically, structurally and tribologically. The produced film exhibited a low friction coefficient, low wear rate and significantly high wear life. This development was attributed to (002) basal plane orientation which is chemically inert, and low %Ti content and the use of pulsed-dc which is offers a stable deposition process, and also the accordance between the hardness values of substrate and film.

STRESS-RELIEF SOLUTIONS FOR BRITTLE TiB2 COATINGS

Engineering applications of TiB2 coatings are limited because of the brittle nature of interfacial bonds on the substrate surfaces, although they have many major properties such as high hardness, high wear and high temperature strength. To overcome this drawback, many researchers have studied over many years and their efforts have taken several forms such as the rotation of substrate, heating treatment during deposition or after deposition, application of positive bias voltage to the substrate, the introduction of transition elements as an interlayer, gradient or multilayer or composite strengthening, and the optimization studies performed by changing deposition process types and/or process parameters such as working gas and bias voltage. The purpose of this paper is to discuss these solutions proposed or developed by researchers against the limited use of TiB2 coatings due to its brittleness and low adhesion. From the results reported in literature, it is concluded that the best solution in order to produce non-brittle TiB2 based film well adherent to substrate is the use of pulsed-dc deposition technology provided that the process parameters are tuned to give an appropriate composition and/or a coating design. Furthermore, the TiB2 based coatings with multiphase layers seem to give better results respect to adherence.

Production of hard hydrophilic Ni-B coatings on hydrophobic Ni-Ti and Ti-6Al-4V alloys by electroless deposition

Abstract This paper is mainly focused on the wetting state of liquid droplets on Ni-Ti and Ti-6Al-4V hierarchical structured hydrophobic surfaces in micro/nanoscale. Electroless Ni-B deposition as a surface coating treatment has recently drawn considerable attention of researchers owing to remarkable advantages when compared with other techniques such as low price, conformal ability to coat substrates, good bath stability and relatively easier plating process control. The Ni-Ti and Ti-6Al-4V substrates were plated by electroless Ni-B plating process. The coated films were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), hardness testing and static contact angle measurement. Results obtained from the analyses show that electroless Ni-B deposition may improve the hardness and wettability of the Ni-Ti and Ti-6Al-4V alloy surfaces.

Synergistic effect of bias and target currents for magnetron sputtered MoS2-Ti composite films

Abstract In terms of modification of the properties of MoS2-Ti composite films, especially tribological properties, significant advances have recently been recorded. However, the commercially production of MoS2-Ti composite films is still limited, because the production of desirable MoS2-Ti composite coating is only possible by using closed field unbalanced magnetron systems and by the selection of convenient deposition parameters. This requirement has focused the researchers’ attention on optimization of deposition parameters. This study is concentrating on the effect of the bias voltage and the target currents for MoS2-Ti composite films deposited by pulsed magnetron sputtering (PMS). It is found that the bias and the target currents clearly affect the mechanical, structural and tribological properties of MoS2-Ti films.