Tomasz Borowski

Effect of the heating temperature on the corrosion resistance of alkali-treated titanium.

The paper presents the results of examinations of the corrosion resistance of titanium after its being subjected to the surface modification by the alkali- and heat-treatments. The material examined was commercially pure titanium (grade 2). The samples were soaked in an aqueous 10M NaOH solution at 60 degrees C for 24 h and subsequently heated at 500, 600, or 700 degrees C for 1 h. The chemical composition of the surface layers was determined by X-ray photoelectron spectroscopy and secondary ion mass spectroscopy. The phases present in the layers were identified by XRD. The corrosion resistance was evaluated by electrochemical methods (Sterns method, potentiodynamic method, and impedance spectroscopy) at a temperature of 37 degrees C after short- and long-time exposures. The 13 h exposure was aimed to allow the corrosion potential to stabilize. The aim of the long-term exposures was to examine how the corrosion resistance of the modified samples changes during the exposure. Under the conditions prevailing during the experiments, the highest corrosion resistance was achieved with the samples heated at a temperature of 700 degrees C.

Thermal Stability of Athermal and Deformation Martensite in Ni27Ti2AlMoNb Steel

The study was devoted to the thermal stability of the phases present in chromium-less and practically carbon-less Ni27Ti2AlMoNb steel. Steel with an austenitic structure was subjected to martensitic transformations using a thermal treatment, namely cooling to below the temperature Ms (beginning of the martensitic transformation), or by plastic deformation using the TRIP effect. The cooling in liquid nitrogen gave a martensitic-austenitic structure with athermal martensite α’a. The martensite had a lenticular morphology, and its volumetric share was 51%, which is typical of duplex type steels. The 50% squeeze of the austenitic steel resulted in the formation of deformation martensite α’d with a lamellar structure (this transformation is only possible below a certain temperature Md). During the experiments, the thermal stability of the two phases, α’a and α’d, at temperatures of 450°C and 550°C was examined. The changes taking place in the steel structure when the athermal martensite and deformation martensite were annealed below and above the temperature As (beginning of the austenitic transformation) were observed using a vibrating sample magnetometer and an optical microscope.

Magnetic Force Microscopic Description of the Structure of Glow Discharge Nitrided Layers Produced on Ni27Ti2AlMoNb Steel

The paper analyzes the magnetic properties and stability of austenite, athermal martensite, and deformation martensite that form in Ni27Ti2AlMoNb steel subjected to glow discharge assisted nitriding, and also of nitrogen austenite (S phase with various lattice constants) which occurs when the nitriding process is conducted below the temperature As. The analysis of these structural components and their morphology was performed using a magnetic force microscope (MFM), whereas the phase composition of the nitrided layers produced on this steel was determined by X-ray diffraction.

Oxynitrided Surface Layer Produced On Ti6Al4V Titanium Alloy Under Low Temperature Glow Discharge Conditions For Medical Applications

In spite that titanium oxides increase biocompatibility of titanium implants but their functional life is limited due to the problems arising from brittles and metalosis. Therefore technology, that allow to produce composite surface layer with controlled microstructure, chemical and phase composition and surface morphology on titanium alloy and eliminates the oxides disadvantages has been existing till now is searched. The requirements of titanium and its alloys implants can be fulfill by the low—temperature glow discharge assisted oxynitriding.The paper describes the surface layer of TiO2+TiN+Ti2N+αTi(N) type produced at temperature 680° C that preserves mechanical properties of titanium alloy Ti6Al4V. Characteristics of produced diffusion multi‐phase surface layers in range of phase composition, microstructure (SEM, TEM, XRD) and its properties, such as frictional wear resistance are presented. The biological properties in dependency to the applied sterilization method are also analyzed.Properties of pr...