The mechanical properties and surface topography of TiN/TiO2 coatings deposited by reactive magnetron sputtering on electron beam surface treated Ti5Al4V substrates were studied. The phase ...composition and crystallographic orientation were studied by X-ray diffraction. The hardness was investigated by nanoindentation test. The surface topography was evaluated using atomic force microscopy.
The results show that polycrystalline TiN and anatase - TiO2 phases are present in all cases. The electron beam treatment (EBT) leads to a more symmetrical distribution of the heights in comparison with the untreated substrates, as well as to increase in the surface roughness. The hardness of the Ti5Al4V substrates before and after the electron beam treatment process increases which is due to the transformation α+β to α′ martensitic microstructure occurring due to the fast cooling rate after the melting process. EBT leads to increase the surface roughness from 8 nm to 25 nm for the deposition of TiN/TiO2 coatings on Ti5Al4V. The treatment of Ti5Al4V substrates leads to decrease in the hardness of the coatings - from 7 GPa to 6 GPa. The scratch tests of the coated samples confirm the decrease of the friction coefficient as compared with the uncoated substrates.
•The mechanical properties and the topography of TiN/TiO2 coatings on Ti5Al4V substrates, deposited by reactive magnetron sputtering has been studied.•Polycrystalline TiN and anatase - TiO2 phases are present in all cases.•The electron beam treatment leads to an increase in the surface roughness.•The hardness of the Ti5Al4V substrates before and after the electron beam treatment process increase.•EBT of Ti5Al4V substrates leads to decrease in the hardness of the coatings - from 7 GPa to 6 GPa.
Abstract
In this study, we demonstrate a combined treatment technique of R18 high-speed tool steel comprising deposition of a WN coating followed by electron-beam surface treatment (EBT). In order to ...understand the influence of the deposited WN coating on the resultant structure and properties, an uncoated specimen was directly electron-beam treated under the same EBT technological conditions. The structure of the specimens was studied by X-ray diffraction, scanning electron microscopy, and energy-dispersive X-ray spectroscopy. The microhardness was also investigated. The phase composition consisted of a double phase structure of Fe and M
6
C carbides in both cases. The microstructure was significantly finer in the case of an EBT of the steel with WN coating, leading to a much higher microhardness in comparison with the case without WN.
Abstract
In the present study, TiN and VN surface coatings are applied on copper substrates, and their influence on the electrical contact resistance (ECR) of the primary material is studied. The ...coatings are deposited using reactive magnetron sputtering in an Ar/N
2
environment. The formed TiN and VN thin films have a thickness of 600 nm and 350 nm, respectively. The preferred crystallographic orientation of both coatings is in the (311) plane. This corresponds to a high crystallite size, high plastic deformations, and high mobility of any structural defects. The I(200)/I(111) ratios of the coatings indicate that the deposited TiN coating is perfectly stoichiometric, and the VN one is hyper stoichiometric, resulting in its’ slightly higher electrical contact resistance. The electrical contact resistance of both coatings is significantly lower compared to that of the pure copper substrate due to their excellent corrosion resistance.
We report electron-beam surface alloying of Ti substrates with Ta. The Ti substrates were covered by a Ta coating with a thickness of 2 μm. The samples were alloyed by a scanning electron beam, with ...the beam deflection geometry in the shape of the infinity symbol (∞). Two experiments were implemented, where the width of the infinity symbol was kept constant at 8 mm, while the height was 8 mm for the first experiment and 4 mm for the second one. The phase composition of the specimens produced was studied by X-ray diffraction (XRD). The microstructure and chemical composition were investigated by scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX), respectively. The results showed that the phase composition consisted of a double phase structure of α' martensitic and of beta phases. Some amount of pure Ta remained in the alloyed layer produced by the first experiment. Also, the distribution of the alloying element into the substrate was significantly more homogeneous in the case of the second one.
Three-component surface alloys of the Ti-Al-Nb and Ti-Al-V systems were formed by means of selective electron beam alloying; the procedure involved DC magnetron sputtering deposition of multilayer Al ...and Nb or Al and V films with a thickness of 1 μm of each layer on a commercially-pure Ti substrate. The samples prepared were then electron-beam surface-alloyed under identical technological conditions. The specimens were examined by scanning electron microscopy (SEM); their chemical composition was studied by energy dispersive X-ray spectroscopy (EDX). X-ray diffraction (XRD) was used to determine the crystallographic structure. Intermetallic alloys in the system of Ti-Al-V were successfully produced with an electron beam current of 15 mA. As the current was increased from 15 mA to 20 mA, only pure titanium was visible, probably due to the evaporation of the alloying materials. In the Ti-Al-N system, intermetallic alloys were formed when the electron beam current reached 25 mA.
The paper reports on the effect of the substrate temperature (350 °C, 380 °C and 420 °C) during reactive magnetron sputtering of a TiN film on the phase composition, texture and mechanical properties ...of TiN/TiO2 coatings on 304L stainless steel substrates. Pure Ti was used as a cathode source of Ti. The texture and unit cell parameters of both TiN and TiO2 phases of the coating are discussed in relation with the tribological properties and adhesion of the coating. The scratch tests performed showed that the nitride deposited at 380 °C, having the highest unit cell parameter and a predominant (111) texture, possessed the lowest friction coefficient (μ), tangential force and brittleness. The anatase-type TiO2 with predominant (101) pole density and increased c unit cell parameter showed the highest stability on the nitride deposited at 420 °C. The results indicated that the friction coefficient, tangential force and critical forces of fracture could be varied by controlling the coating deposition temperature.
This paper aims an investigation of the microstructure and crystallographic structure as well as the thermal stability of Al–Ti–Nb formed by selective electron beam surface alloying. The fabrication ...of the samples has been carried out using circular sweep mode, as two velocities of the sample movement have been chosen:
V
1
= 1 cm/s and
V
2
= 0.5 cm/s. The studied microstructure and crystallographic structure have been investigated by X-ray diffraction (XRD) and Scanning electron microscopy (SEM) respectively. The thermal behavior of the obtained surface alloys are evaluated by the coefficient of thermal expansion (CTE) which has been evaluated by neutron diffraction measurements at high temperature. The results show that in the earlier stages of formation, the microstructure of the intermetallic phase is mainly in the form of coarse fractions, but at the following moments they dissolve, forming separated alloyed zone and base Al substrate as the alloyed zone consists of fine (Ti,Nb)Al
3
particles dispersed in the Al matrix with small amount of undissolved intermetallic fractions. Formation of preferred crystallographic orientation as a function of the speed of specimen motion has not been observed. The performed neutron diffraction measurements show that the lattice parameters of the obtained intermetallic (Ti,Nb)Al
3
are less upshifted in comparison to pure Al. It has been found that the aluminium lattice is much more unstable at high temperatures than that of the intermetallic phase. The CTE for the intermetallic phase is 8.70 ppm/K for
a
axis and 7.75 ppm/K for
c
axis respectively while considering Al it is 12.95 ppm/K.
The effect of the deposition technology of gradient TiN/TiO2 coatings, applied on Ti5Al4V substrate, on the phase composition and mechanical properties has been studied. The films have been applied ...by reactive magnetron sputtering and cathodic arc and glow-discharge techniques. The coatings' properties have been studied by X-ray diffraction (XRD) and nanoindentation tests. The results in the present study show that the application of both methods are capable to form polycrystalline TiN and TiO2. The coatings deposited by magnetron sputtering are monophasic and polycrystalline as TiO2 is in the form of anatase. Those, applied by cathodic arc and glow-discharge technique, TiO2 layer is in the form of double-phase structure of rutile and anatase. The measured hardness is similar for the coatings deposited via both methods. The hardness of magnetron sputtered coatings is 6.3±1.1 GPa. The values for coatings obtained by glow-discharge is 6.1±1.4 GPa.
We present a detailed investigation of the synthesis and mechanical properties of Ti-Al-Nb coatings, formed by alloying of Ti substrates with Al and Nb films by selective electron-beam melting (SEBM) ...via continuous electron beam. A cycling mixing of pre-deposited bilayer Al/Nb films with a Ti substrate is realized, where the maximum number of the cycles is 3. The first one is a SEBM of a bilayer Al/Nb coating deposited on pure Ti substrate. The obtained after the first cycle specimen is further coated with the same bilayer coating and then subjected to a second SEBM cycle; the same procedure is repeated for the third cycle. The alloyed layers are characterized using Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Spectroscopy (EDX), and X-ray Diffraction (XRD). The microhardness is also studied. The thickness of the coatings obtained after each cycle is in the range from 20 μm to 24 μm. The specimen obtained after the first cycle exhibits an alloyed zone consisting of pure Ti with a small content of Al and Nb, while those manufactured by the following cycles represent Ti2AlNb based phases. The microhardness increases from 180 HV0.03 for the pure Ti substrate to 570 HV0.03 after the third cycle.
•Ti-Al-Nb alloys were obtained by additive electron beam cycling mixing technique, as the number of the cycles is 3.•The 1st cycle is electron beam melting (EBM) of Ti substrate with a bilayer Al/Nb coating.•The 2nd and 3rd cycles are EBM of the samples obtained by the 1st and 2nd processes with the same bilayer Al/Nb coating.•Ti2AlNb based surface alloy was obtained after the third cycle.•The hardness increases from 180 HV for the pure Ti to about 570 H V after the third cycle.
•Al–Ti–Nb surface alloys have been successfully obtained by electron-beam surface alloying technology.•The alloys consist of (Ti,Nb)Al3 fractions, distributed in the biphasic structure of (Ti,Nb)Al3 ...particles dispersed in α-Al.•The alloying speed does not affect the lattice parameters of (Ti,Nb)Al3 and, does not form additional stresses, strains etc.•It was found that lower velocity of the specimen motion during the alloying process develops more homogeneous structures.•The measured hardness of (Ti,Nb)Al3 compound reaches 775HVkg/cm2 which is much greater than the values of NbAl3.
The combination of attractive mechanical properties, light weight and resistance to corrosion makes Ti-Al based alloys applicable in many industrial branches, like aircraft and automotive industries etc. It is known that the incorporation of Nb improves the high temperature performance and mechanical properties. In the present study on Al substrate Ti and Nb layers were deposited by DC (Direct Current) magnetron sputtering, followed by electron-beam alloying with scanning electron beam. It was chosen two speeds of the specimen motion during the alloying process: V1=0.5cm/s and V2=1cm/s. The alloying process was realized in circular sweep mode in order to maintain the melt pool further. The obtained results demonstrate a formation of (Ti,Nb)Al3 fractions randomly distributed in biphasic structure of intermetallic (Ti,Nb)Al3 particles, dispersed in α-Al solid solution. The evaluated (Ti,Nb)Al3 lattice parameters are independent of the speed of the specimen motion and therefore the alloying speed does not affect the lattice parameters and thus, does not form additional residual stresses, strains etc. It was found that lower velocity of the specimen motion during the alloying process develops more homogeneous structures. The metallographic analyses demonstrate a formation of surface alloys with very high hardness. Our results demonstrate maximal values of 775HV kg/cm2 and average hardness of 673HV kg/cm2.
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