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Abstract: Several theoretical and experimental studies have been carried out in recent years aimed at enhancing the mechanical resistance and osseo-integration of titanium based dental implants. The often inadequate mechanical properties of commercially pure titanium (CpTi) can lead to the clinical failure of dental materials. A plasma immersion ion implantation (PIII) process has been applied to CpTi samples in an optimized nitrogen/oxygen gas mixture at middle and high temperatures, improving considerably the properties of these. Studies of microhardness, corrosion, AFM, XRD and Raman spectroscopy have been applied in order to evaluate the treated samples whereby highly biocompatible TiO2 (Rutile) and TiNx layers have been identified. A high corrosion tolerance was found for CpTi, indicating a typical passive behavior of titanium, which can be attributed to a highly stable film formed on the samples placed in Hank's solution. The hardness was improved nearly five times with respect to that of the control material. [Copyright &y& Elsevier]

Abstract: A study of the plasma ion implantation (PIII) of commercially pure titanium (CpTi) at a low voltage (<4kV) is presented. The processed samples were treated in divers mixtures of O and N in order to achieve biocompatible oxidized and nitrided layers as well as to enhance their superficial hardness. In this way, the low wearing resistance of CpTi can be avoided while creating a biocompatible rutile phase titanium oxide layer for a better bone integration. A form of synergy associated to the dependence of microhardness on the implanted layer disposition is identified. Thus, an upper rutile layer is immediately followed by another one, in which titanium, a nitride (TiN0.26) and rutile coexist. The latter leads to a superior microhardness performance. Most of all these surface treatments of titanium, when applying an 80%N–20%O mixture, yield higher corrosion resistance parameters with respect to the main metallic materials used in prosthetics, including the Co–Cr–Mo alloys, albeit excluding CpTi. [Copyright &y& Elsevier]

Abstract: Better protective and functional coatings on dental drills are increasingly demanded for their desired mechanical, tribological or chemical properties. We have studied the surface modification of steel dental drills, with an aim to increasing both their cutting life and corrosion resistance in dentistry using low-energy plasma-immersion nitrogen implantation over different temperature ranges. The temperature of the drills was controlled by varying the implantation voltage. Following implantation, tests showed that the microhardness of the nitrided drill surfaces was approximately one order higher than that of untreated drills and the corrosion tolerance was found to increase with growing temperature of the plasma-immersion process. [Copyright &y& Elsevier]

Abstract: A study is reported of the influence of both temperature and nitrogen gas pressure on the microhardness and corrosion resistance of AISI 304 stainless steel, PIII treated in a DC plasma discharge in a toroidal chamber. The sample temperatures were stabilised at various gas pressures within the range 1×10−3 to 2×10−1 mbar by adjusting the pulse duration (50–75μs) while maintaining constant the bias voltage (−5kV) and pulse frequency 1kHz. It was found that treatment below ∼520°C substantially enhances the microhardness as well as the corrosion resistance of the samples. The experiments also showed that treating the samples at temperatures above ∼520°C adversely modifies the properties associated with corrosion resistance. [Copyright &y& Elsevier]

Abstract: PIII technology has been applied in vacuum chambers with toroidal and cylindrical geometries in order to study the nitriding of AISI 304 austenitic stainless steel plates. A high voltage generator provided a 5kV polarization in 5μs long pulses at 1kHz in a nitrogen plasma created by a DC source. An elemental analysis of the samples was performed by means of SEM while XRD was used to determine the characteristic patterns of their nitrides. Results indicate a significant increment in the implanted nitrogen content of the substrata. The detected nitrides were identified as Fe3NiN and FeNiN, which are associated with the enhanced austenitic phase of the stainless steel. Thus, the Vickers microhardness of the samples doubles in the cylindrical chamber and reaches a 2.8 times increase in the toroidal one. It is also observed that this microhardness tends to grow with the gas pressure, and therefore with the sample temperature, as well as with the thickness of the nitrided stratum. [Copyright &y& Elsevier]

Abstract: Significant improvements in the surface properties of austenitic AISI 304 stainless steel by the use of PIII technology in nitrogen plasmas have been demonstrated. Yet, such treatments, often focused on the development of microhardness, can affect adversely the corrosion performance of the samples. Several results in this direction are presented in this work which have been obtained from the PIII processing of stainless steel plates in a nitrogen plasma within a toroidal chamber. This geometry presents a potential for turbulence which, in turn, should enhance the collisional effects and better the plasma densities. The main relevant structural, mechanical and corrosion wise properties of the samples were analyzed by XRD, SEM, Vickers microhardness, surface profilometry and electrochemical methods. The results indicate that at a low temperature range (below some 250 °C) both microhardness and corrosion resistance improve. At middle temperature ranges (in the order of 250–400 °C) chromium nitride tends to precipitate affecting the austenitic phase and therefore leading to a decline in the tolerance to corrosion albeit to a substantial increase in the sample microhardness. Finally, at higher temperatures, microhardness grows dramatically along with the implantation depth while a significant reduction in the corrosion performance is observed. [Copyright &y& Elsevier]