J. Baszkiewicz

Effect of calcium-ion implantation on the corrosion resistance and biocompatibility of titanium

This work presents data on the structure and corrosion resistance of titanium after calcium-ion implantation with a dose of 10(17) Ca+/cm2. The ion energy was 25 keV. Transmission electron microscopy was used to investigate the microstructure of the implanted layer. The chemical composition of the surface layer was examined by XPS and SIMS. The corrosion resistance was examined by electrochemical methods in a simulated body fluid (SBF) at a temperature of 37 degrees C. Biocompatibility tests in vitro were performed in a culture of human derived bone cells (HDBC) in direct contact with the materials tested. Both, the viability of the cells determined by an XTT assay and activity of the cells evaluated by alkaline phosphatase activity measurements in contact with implanted and non-implanted titanium samples were detected. The morphology of the cells spread on the surface of the materials examined was also observed. The results confirmed the biocompatibility of both calcium-ion-implanted and non-implanted titanium under the conditions of the experiment. As shown by TEM results, the surface layer formed during calcium-ion implantation was amorphous. The results of electrochemical examinations indicate that calcium-ion implantation increases the corrosion resistance, but only under stationary conditions; during anodic polarization the calcium-ion-implanted samples undergo pitting corrosion. The breakdown potential is high (2.7-3 V).

Effect of phosphorus-ion implantation on the corrosion resistance and biocompatibility of titanium

This work presents data on the structure and corrosion resistance of titanium after phosphorus-ion implantation with a dose of 10(17)P/cm2. The ion energy was 25keV. Transmission electron microscopy was used to investigate the microstructure of the implanted layer. The chemical composition of the surface layer was examined by X-ray photoelectron spectroscopy and secondary ion mass spectrometry. The corrosion resistance was examined by electrochemical methods in a simulated body fluid at a temperature of 37 C. Biocompatibility tests in vitro were performed in a culture of human derived bone cells in direct contact with the materials tested. Both, the viability of the cells determined by an XTT assay and activity of the cells evaluated by alkaline phosphatase activity measurements in contact with implanted and non-implanted titanium samples were detected. The morphology of the cells spread on the surface of the materials examined was also observed. The results confirmed the biocompatibility of both phosphorus-ion-implanted and non-implanted titanium under the conditions of the experiment. As shown by transmission electron microscope results, the surface layer formed during phosphorus-ion implantation was amorphous. The results of electrochemical examinations indicate that phosphorus-ion implantation increases the corrosion resistance after short-term as well as long-term exposures.

Nitrogen transport mechanisms in low temperature ion nitriding

Abstract The aim of the study was to find whether the basic phenomena that occur during the glow discharge assisted nitriding of metal differ from those occurring during gaseous nitriding. To define the specificity of a glow discharge assistance a simple model system such as an iron cathode nitrided in d.c. glow discharge in nitrogen at a low temperature was examined. The Fe 4 N layer of thickness 0.8 μm and 1.5 μm was produced in 5 h at 275°C and 3 h at 350°C, respectively. The results were compared with experimental data of gaseous nitriding and computer aided simulations based on the Lehrer (NH 3 –H 2 ) 1.5 (Fe–N) equilibrium diagram. The thickness of the Fe 4 N layer produced in our experiment was greater than the thickness of the Fe 4 N layer produced in the gaseous process observed experimentally and as the estimated values from the model based on the equilibrium diagram, in spite of the fact that the total number of N atoms in the gaseous process was 40÷80 times greater than in the glow discharge assisted process. Based on the relation ΔN= k √ Dt we proposed that the difference between the gaseous nitriding process and the glow discharge assisted nitriding process results from the difference in the values of k , which in turn depend on the N level at the diffusion front. The higher N level can be explained in terms of a shallow ion implantation.

Effect of plasma electrolytic oxidation in the solutions containing Ca, P, Si, Na on the properties of titanium†

The surface layers were formed on titanium by plasma electrolytic oxidation (PEO) in the solutions which contain various amounts of Na(2)SiO(3)x5H(2)O, Na(3)PO(4) x12H(2)O and Ca(CH(3)COO)(2) xH(2)O. The layers were characterized using a scanning electron microscope (SEM) coupled with an energy dispersive spectrometer (EDS) and an X-ray diffractometer (XRD). The titanium/oxide surface layer interface was analyzed by X-ray photoelectron spectroscopy (XPS). The adhesive strength of the oxide layers was evaluated by the scratch-test. The bioactivity of the surface was determined by soaking in a simulated body fluid (SBF) for 7 and 30 days. The corrosion resistance was determined by electrochemical methods after 13, 181, and 733 h exposure in SBF at a temperature of 37°C. The oxide layers obtained were rough and porous and enriched with Ca, P, Si, and Na and their properties depended on the concentration of the components of the electrolyte. The results of the electrochemical examinations, after a 13 h exposure in SBF, show that the surface modification by PEO improves the corrosion resistance of titanium and it is not degraded after a long-term exposure in SBF. The electrochemical impedance spectroscopy (EIS) results indicate that the surface layers have a complex structure.

Regular paperEffect of nitrogen ion implantation on the structure and corrosion resistance of OT-4-0 titanium alloy

This work presents data on the properties of the surface layer of OT-4-0 titanium alloy after nitrogen implantation. Polished samples were implanted with nitrogen doses of 1 × 1017 and 6 × 1017 cm−2. The corrosion resistance was examined by the potentiodynamic method in 0.5 M NaCl and 15% H2SO4 solutions. Transmission electron microscopy was used to investigate the microstructure of the implanted layers formed on OT-4-0. It was found that the implanted layers consist of a dispersion of fine TiN particles in a deformed matrix of α-Ti. Nitrogen implantation increases the corrosion resistance and microhardness.

Implantation of silicon ions into a surface layer of the Ti6A14V titanium alloy and its effect upon the corrosion resistance and structure of this layer

The effect of silicon ion implantation upon the corrosion resistance and structure of the surface layers formed during the implantation in the Ti6A14V titanium alloy was examined. The silicon doses were 0.5, 1.5, 3.0 and 4.5 × 1017Si+/cm2, and the ion beam energy was 100 keV. The corrosion resistance of the samples exposed to a 0.9% NaCl solution at a temperature of 37 °C was measured using electrochemical methods. The structure of the surface layers formed during the implantation was examined by a transmission electron microscope (TEM). The results of the corrosion resistance examinations have shown that the unimplanted and 0.5 × 1017Si+/cm2 implanted samples undergo uniform corrosion. At higher silicon doses, the samples show pitting corrosion. The highest corrosion resistance was shown by the alloy implanted with 0.5 × 1017Si+/cm2. It has been found that, after a long-term (1200 h) exposure to a 0.9% NaCl solution, the corrosion resistance of the samples is greater than that observed after a short-term exposure. TEM examinations have shown that, beginning from a dose of 1.5 × 1017Si+/cm2, the surface of the Ti6A14V alloy samples becomes amorphous. Heating of the 1.5 × 1017Si+/cm2 implanted samples at 200 and 500 °C does not change their structure, whereas after heating at 650 °C, the amorphous phase vanishes.

Effect of oxygen implantation upon the corrosion resistance of the OT-4-0 titanium alloy

Abstract The properties of the surface layer on the OT-4-0 titanium alloy after oxygen implantation were examined. Polished samples were implanted with doses of 5 × 10 16 and 1 × 10 17 O + cm −2 . The O + ion energy was 50 keV. Transmission electron microscopy has been used to investigate the microstructure of the implanted layers formed on the OT-4-0. It was found that the implanted layers are nanocrystalline rutile (TiO 2 ). Depth profiles of oxygen and titanium were investigated by SIMS and corrosion resistance was analysed by electrochemical techniques. The results indicate that the oxygen implantation increases the corrosion resistance of the OT-4-0 titanium alloy.

Effect of silicon-ion implantation upon the corrosion properties of austenitic stainless steels

The structure of the surface layers and the corrosion resistance of austenitic stainless steels after silicon-ion implantation, were examined. The implanted silicon doses were 1.5×1017, 3×1017 and 4.5×1017 Si+ cm-2. Implantation with all these doses gave an amorphous surface layer. When samples implanted with 1.5×1017 Si+ cm-2 were annealed at temperatures of 300 and 500 °C, their surface structure remained unchanged. After annealing at 650 °C, the amorphous layer vanished. It was determined how, in terms of corrosion resistance, the amount of implanted silicon, subsequent heat treatment and long time exposure, affect highly corrosion-resistant austenitic stainless steel (18/17/8) in comparison to the 316L austenitic stainless steel subjected to the same treatment. Corrosion examinations were carried out in 0.9% NaCl at a temperature of 37 °C. After silicon-ion implantation the corrosion resistance of the 316L steel increased while that of highly resistant (18/17/8) did not. The corrosion resistance of the investigated steels, both implanted and non-implanted, increased with the exposure time of the samples in the test environment.

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.

Corrosion properties of silicon-on-steel ion beam mixed layers

Abstract Preliminary results of the study of corrosion properties of ion beam mixed Si layers on AISI 316L steel are presented. The basic mixing parameters such as mixing efficiency and the thickness of residual Si layers were determined by means of the RBS technique. The corrosion process was studied using the potentiodynamic method. The results show a substantial change in the corrosion mechanism of ion beam mixed layers. Pitting corrosion characteristic for virgin or Si implanted samples is replaced by a crevice corrosion in the case of ion beam mixed ones. This is very likely due to the formation of brittle, high Si concentration layer susceptible to crevice corrosion that leads to the scalling of surface layer. The results obtained for both, ion implanted and Si ion beam mixed samples, indicate that steel layers with relatively low (∼ 20 at%) Si content exhibit superior corrosion resistance.