Jolanta Baranowska

The Kinetics of Gas Nitrided Layer Growth on Austenitic Stainless Steel

This paper presents the results of investigations on gas nitrided austenitic stainless steel. The treatment was conducted at various temperatures (400-515°C), gas compositions of atmospheres used (20-100% NH3) and times (0.5-12h). The layers were investigated by X-ray diffraction, Light and Electron Microscopy and Glow Discharge Optical Spectrometry. The kinetics of layer growth has been analysed in terms of the process parameters and compared with the data presented for plasma treated steel. The specific nitrogen profiles of nitrided layers are discussed in the context of the layers’ microstructure and phase composition.

The Influence of Chemical Composition of Stainless Steel on the Formation of Low Temperature Nitrided Layer

This paper presents results of investigations on gas nitride layers of stainless steel. Steel with ferritic structure, containing different chromium and nickel content was used in the experiments in order to compare the influence of these two main alloying elements on layer growth kinetics and layer structure. Particular attention was paid to formation of Sphase and expanded martensite which usually are formed during lowtemperature nitriding of stainless steel. It was observed, that chromium and nickel content does not have a significant influence on layer growth kinetics but the treatment temperature does. It was also stated that Sphase formation is possible both in nickel alloyed and nickelfree steel depending on treatment parameters.

Influence of substrate temperature and gas pressure on aluminum oxynitride coatings obtained by pulsed laser deposition

Abstract The paper presents results of the investigation on the influence of deposition parameters, such as substrate temperature, total gas pressure and reactive gas composition on the structure, chemical composition and mechanical properties of aluminum oxynitride coatings obtained by pulsed laser deposition (PLD) method. Selection of process parameter ranges, which could be promising for aluminum oxynitride (ALON) coatings deposition, was the main objective of the work. Two series of experiments were carried out with varied pressure and temperature. It was found that from the chemical composition viewpoint, the most promising are atmospheres containing 20 % to 40 % oxygen. The nitrogen to oxygen ratios in the coatings can be controlled by increasing the total pressure or substrate temperature. However, increasing the pressure has a negative effect on the O + N:Al ratio, mechanical properties and quality of the coatings. The influence of temperature is much less drastic and more controllable. Increasing the deposition temperature is much more beneficial since it improves the mechanical properties and can compensate to some extent the negative effect of the total pressure. From the coating quality viewpoint, it is possible to establish an optimum temperature range for which the coatings are characterized by a compact structure and a limited number of droplets.

Influence of atmosphere composition on the structure and properties of aluminum oxynitride coatings deposited by PLD method

This work presents studies on the influence of oxygen content in reaction atmosphere during pulsed laser deposition on the structure and properties of aluminium oxynitride films. The coatings were grown on monocrystalline Si substrates. Aluminium nitride bulk disk was used as a target. The film deposition took place at room temperature and pressure of 0.5 Pa with varying content of oxygen and nitrogen. Thickness and roughness of the coatings were measured by profilometer. The X-ray diffractometer (XRD) was used for phase analysis of the coatings. Chemical composition was evaluated using X-ray microanalysis (EDS) by means of scanning electron microscopy (SEM). The surface topography was examined using an atomic force microscopy (AFM). Hardness of the coatings was measured by means of nanoindentation. Adhesion was evaluated in microscratch tests and the morphology of the residual scratch was characterized by AFM. Results showed that it was possible to obtain coatings composed of oxynitrides with different stoichiometry. Mechanical properties of the obtained coatings, however, were significantly different from those demonstrated by ALON ceramic. The content of oxygen in the coatings had an influence on the decreasing hardness and Young’s modulus and improved adhesion. There was no influence on thickness and roughness but the lowest number of droplets was noticed in the coatings obtained in pure oxygen.

Stresses in the Surface Layer and Hydrogen Absorption and Diffusion in Cavitation Condition

Cavitation attack in liquids generated a various states of stresses in surface layers of metals. Differences in stress state effects on hydrogen absorption activated by the cavitation implosion. Results of XRD investigation and FEM modeling shows on inhomogenity of process.

Ferromagnetic and spin wave resonances in thin layer of expanded austenite phase

Four samples of austenite coatings deposited by reactive magnetron sputtering on silicon substrate at four different temperatures and pressures were investigated by ferromagnetic resonance (FMR) method at room temperature. The expanded austenite phase S (γN) layers with thickness in the 160–273 nm range and concentration of magnetic atoms: 72 % Fe, 18 % Cr and 10 % Ni, were obtained. The coatings with nanometric size grains were strongly textured and grown mostly in [100] direction, perpendicular to the sample surface. Intense FMR spectra were recorded at various angles between the static magnetic field direction and the sample surface. A strong magnetic anisotropy of the main uniform FMR mode was observed and the effective magnetization 4πMeff determined. Spin wave resonance (SWR) modes were observed in all investigated samples in out-of-plane geometry of the magnetic field. The resonance fields of SWR modes in our samples varied linearly with the spin wave mode number. The value of the effective magnon stiffness constant was determined assuming a parabolic shape of the magnetization variation across the sample thickness.

Structure and Properties of Gas Nitrided Layers on Nanoflex Stainless Steel

The paper presents results of research on nitrided layers on Sandvik NanoflexTM precipitation hardened stainless steel. The influence of process parameters on nitriding kinetics and structure of the layers was investigated. The gas nitriding process was conducted in a mixture of ammonia 50% and products of its dissociation, as well as in 100% ammonia atmosphere at temperature range 400500°C and time between 2 and 8 h. The obtained diffusion layers were examined using the following methods: light and scanning electron microscopy, XRD phase analysis and EDS chemical analysis. Mechanical properties were tested with hardness measurements. It was found that kinetics depends on treatment temperature and nitrogen potential of the atmosphere. Moreover, treatment conditions affecting Sphase formation and expanded martensite in nitrided layers are discussed.

Gas Nitriding of Sintered Austenitic Stainless Steel

The results concerning gas nitriding of sintered stainless steel are presented in the paper. The samples made of 316L steel were gas nitrided at temperatures between 400-550°C. The microstructure of the layer was investigated by means of light and atomic force microscopy. The phase composition was identified using X-ray diffraction. Moreover, tribological and corrosion properties of the samples were evaluated. It was demonstrated that in case of gas nitriding it is possible to obtain nitrided layers also inside open pores, which can be beneficial for corrosion response of nitrided sintered austenitic stainless steel applied in corrosive environments.

Kinetics of Low Temperature Nitriding of Precipitation Hardened Stainless Steel

The paper presents results of research on nitrided layers on precipitation hardened stainless steel, known also as 1RK91 (Sandvik NanoflexTM). Samples were subjected to low temperature nitriding. The influence of nitriding parameters on nitriding kinetics was investigated. The nitriding process was carried out in a mixture of NH3 50% and products of its dissociation as well as in 100% ammonia atmosphere at temperature range 425-475°C. To investigate the kinetics of nitrided layer formation, the nitriding time changes between 2 and 8 h. The obtained diffusion layers were examined using the following methods: light and scanning electron microscopy, XRD phase analysis. The distribution profiles of selected chemical elements were acquired using optical spectrometry GDOES.