Mechanism of liquid stirring in the melt pool formed by a CW-CO₂-laser beam in the process of obtaining surface coating by laser surface alloying (LSA) and laser cladding (LC) has been studied.

It was been shown that in the case of direct injection method (DIM) the pressure exerted from the surface of the melt pool by the transporting gas flow and by injected particles by two order of magnitude higher than the forces of surface tension that govern the movement of liquid in the melt pool formed by laser melting of predeposited coatings. Velocities of liquid movement in the melt pool have been also evaluated. It has been shown that proposed mechanism of liquid movement results in multiple stirring of the melt that account for the observed chemical and structural uniformity of LSA and LC coatings.In the case of a deep melt pool, when its depth is equal to or higher its effective radius, liquid moves only in the plane of laser beam scanning. Metallographic and SEM observations well correlating with the proposed mechanism of LSA and LC coatings formation by DIM are presented.

The variation of reflectivity, index of refraction, real and imaginary part of dielectric function, absorption coefficient and CIE l*a*b* chromatic coordinates of TiN_x coatings due to variation of deposition parameters was investigated. The double and single balanced magnetron depostion system were used in experiments. Reflectivity and ellipsometry measurements, scratch test, calotest and microhardness measurements, as well as STM, SEM and XRD analyses were performed.

The coatings deposited in double magnetron configuration show significant changes of optical, mechanical and structural characteristics due to small variation in nitrogen flow at other parameters kept constant. The reflectance curve was found "sensitive" to small variation of nitrogen flow during deposition process. The position of reflectance minimum on the wavelength scale and its value, as well as the overall shape of reflectance curve of TiN coating depend on nitrogen flow during film growth.

In the case of single balanced magnetron, optical and structural characteristics of deposited TiN_x coatings depend on target to substrate distance. In this case the optical characteristics change during time, which was not the case with the double magnetron deposited samples. In all cases the mechanical characteristics of the coatings were stable during aging. The correlation that exists between some optical and mechanical characteristics of TiN_x coatings may be used to estimate mechanical and structural coating properties only during a limitted time period after deposition

Pulsed laser deposition (PLD) can be utilized to generate films with desired properties quite different from those of the starting material. Since diamond-like carbon (DLC) films grown by PLD using turbo pump are perpared without hydrogenated DLC films. In general, the degree of diamond-like character mainly estimated by the fraction of sp³ hybridized carbon bonding in a film varies considerably with the deposition parameters.

In this study, effects of the substrate temperature, laser energy density, and laser wavelength on the properties of DLC films have been studied by scanning electron microscopy (SEM), X-ray diffraction, Raman spectroscopy, electron energy loss spectroscopy (EELS), electrical conductivity and optical measurements. By varying the deposition temperatures and the laser energy densities from room temperature to 600°C and from 6 to 17 J/cm², respectively, the optimized deposition condition for DLC films has been obtained. The deposition condition of DLC films was optimized at the laser energy density of 12 J/cm² and at the substrate temperature of 300°C, while graphitic films were fabricated at the substrate temperature of 200°C. This optimized deposition condition will contribute the fabrication of high quality DLC films for the use of electron field emission cathodes.

Austenitic stainless steesl are widely used due to their advantageous combination of properties as ductility, strength and excellent corrosion resistance However, due to their moderate hardness they are not suited for abrasively stressed parts. Hence, the market potential of austenitic stainless steels could be greatly enhanced by a technique allowing surface hardening without adversely affecting the corrosion resistance. While techniques as heat treatment, carburizing and gas nitriding fail, plasma ion nitriding is a promising candidate. At moderate temperatures (about 400 °C) the formation of a layer which is characterised by a high content (about 20at.%) of nitrogen in solid solution is well established. Layer thickness up to some tens of μmm and significantly improved hardness and wear and excellent corrosion resistance have been observed.

Normally nitriding can be described in good approximation as diffusion into a semi-infinite solid during constant surface concentration. However, during plasma ion nitriding austenitic stainless steel at moderate temperatures fast nitrogen diffusion and unusual nitrogen concentration profiles have been observed. Additionally, a native surface oxide layer is supposed to act as a diffusion barrier. It has been reported that for constant temperatures the nitriding velocity increases with either current density and ion energy. This gives rise to assume that for high nitriding velocities the surface oxide layer has to be removed by sputtering or that the ion energy and the corresponding ballistic implantation depth has to be sufficient to overcome the barrier. paragarph Since the nitrogen retention is supposed to be affected by the surface oxide layer and therefore by ion implantation, sputtering and re-oxidation from the residual gas a dynamic in-situ ion beam analysis experiment using a crossed beam geometry was set up. Plasma ion nitriding is performed using a Kaufman-type broad-beam ion source. Dynamic depth resolved compositional analysis is performed by elastic recoil detection analysis using a 35MeV chlorine ion beam. Elastic recoil detection analysis is sensitive to light elements as carbon, nitrogen and oxygen and has been optimized regarding fast data acquisition here. Additionally the residual gas is controlled by a quadrupole mass analyzer and a variable gas inlet.

Preliminary results have shown that the nitrogen retention is strongly correlated with the reduction of the surface oxide layer. Quantitative time resolved measurements of the nitrogen concentration profiles will be presented for various oxygen partial pressures, nitrogen ion energies and current densities. The results will be compared with theoretical predictions of the adsorption rate from the residual gas, the ballistic implantation depth and the sputtering rate. The aim is to develop a quantitative transport scenery for plasma ion nitriding austenitic stainless steels at moderate temperatures with emphasis on the role of the surface oxide layer.

The influence of the chemical composition of TiBN compounds on their properties has been studied using reactive cathodic magnetron cosputtering from a Ti and a TiB₂ target. The wide explored zone (0 to 60% N and 0 to 60% B) has shown two ultra hard regions, one with high B and low N content and the other one with medium B and N content. Abrasive wear tests in water have also shown very high wear resistance for the coating with medium B and N content. From these results, a B containing Ti target has been elaborated in order to obtain the B/Ti ratio corresponding to the high abrasive wear resistant coating. Deposition rate has been studied as a function of N₂ flow. Variations of deposition rate have been correlated with cristalline structure transition which shows an unidentified phase for N₂ flow comprised between 0 and 5 sccm. The chemical composition indicates that this phase could be Ti₂B for N₂ flow comprised between 6 and 8 sccm, coatings have fcc structure which lattice parameter decreases when N₂ flow increases. Coatings obtained at N₂ flow over 8 sccm are constituted of a mixture of TiN and tBN. Scratch test measurements indicate good adhesion of the 10 μm thick coatings on the C35E steel. The hardness increases from 10 to 45 Gpa when N₂ flow increases from 0 to 5 sccm and then remains constant. The abrasive wear test has shown the maximum resistance of coatings for 6 sccm N₂ flow. The wear resistance of this TiBN coating is 3 times better than the one of TiN or CrN.

Results obtained from a single B containing target are in good agreement with those obtained using reactive magnetron cosputtering. The coating containing 55% Ti, 19% B and 26% N shows high hardness 45 Gpa) and excellent abrasive wear resistance.