Claudia Beatriz dos Santos

Bio: Claudia Beatriz dos Santos is an academic researcher from Universidade Federal do Rio Grande do Sul. The author has contributed to research in topics: Composite number & Corrosion. The author has an hindex of 3, co-authored 5 publications receiving 91 citations.

Wear–Corrosion Resistance of DLC/CoCrMo System for Medical Implants with Different Surface Finishing

Abstract: The field of medical implants in the human body is a growing area with diverse tribological aspects. This application field has its own specific characteristics, dominated by stringent quality requirements due to the human suffering and sometimes life-threatening consequences of a surface failing to fulfil its required function. Combined wear–corrosion tests could provide more complete information about the implant behaviour in the aggressive body environment than separate wear and corrosion testing. Combined wear–corrosion experiments were performed using a reciprocating ball-on-plate apparatus equipped with an electrochemical cell. Untreated CoCrMo alloy samples as well as diamond-like carbon (DLC) coated samples were used as plate. The DLC coatings were tested with three different surface finishes: as-deposited, polished with diamond and brushed. All DLC coated samples with and without mechanical finishing had lower corrosion activity under wear–corrosion conditions and also smaller wear tracks when compared with the CoCrMo alloy. The current density for the coated alloy was about two orders of magnitude lower on average (10−5 vs. 10−3 A cm−2) and had a final coefficient of friction of only 50% of the uncoated metal (0.15 vs. 0.3). The brushed DLC showed the lowest current density and its behaviour was better than polished DLC and DLC as-deposited up to a potential of +0.93 V.

Heat Treated NiP–SiC Composite Coatings: Elaboration and Tribocorrosion Behaviour in NaCl Solution

Abstract: Tribocorrosion behaviour of heat-treated NiP and NiP–SiC composite coatings was investigated in a 0.6 M NaCl solution. The tribocorrosion tests were performed in a linear sliding tribometer with an electrochemical cell interface. It was analyzed the influence of SiC particles dispersion in the NiP matrix on current density developed, on coefficient of friction and on wear volume loss. The results showed that NiP–SiC composite coatings had a lower wear volume loss compared to NiP coatings. However, the incorporation of SiC particles into the metallic matrix affects the current density developed by the system during the tribocorrosion test. It was verified that not only the volume of co-deposited particles (SiC vol.%) but also the number of SiC particles per coating area unit (and consequently the SiC particles size) have made influence on the tribocorrosion behaviour of NiP–SiC composite coatings.

Corrosion process in NaCl/Na2SO4 solutions of AISI 316L stainless steel treated by ionic nitriding

Abstract: This work is a corrosion study of an AISI 316L austenitic stainless steel after different plasma ion nitriding conditions. The properties of the coated AISI 316L were measured. The corrosion resistance was evaluated by cyclic voltammetry and salt spray testing. Sample surfaces were characterised by SEM and the phase determination with XRD analysis. Nanohardness was determined by using a Vickers indenter. The nitrided samples treated at 400°C, in a gaseous mixture of 5%N2 and 95%H2 for 4 and 5 h, had the best corrosion resistance. For the salt spray test, where the potential range is near the equilibrium potential, the nitrided material presented a reduced corrosion resistance. Through the control of the process parameters it is possible to improve the stainless steel surface hardness, combined with a good corrosion resistance. The highest value of temperature and N2 proportion increased the surface roughness and hardness, though it caused a decrease in corrosion resistance.

Corrosion Resistance of PAPVD TiN Coating on AISI 304 Stainless Steel

Abstract: In this work the corrosion resistance of PAPVD TiN hard coatings on AlSl 304 stainless steel with a titanium interlayer has been addressed. Cyclic voltammetry corrosion tests in NaCl 3.5% solutions were performed for samples prepared by depositing TiN/Ti onto steel using different deposition parameters. The surface morphology of the samples was examined by using a scanning electron microscope (SEM) and phase analysis was performed by X-ray diffraction (XRD). The cyclic voltammetry curves showed two distinct behaviours. Firstly, a reduction in corrosion resistance was observed when current density was increased for the whole potential range studied. The second observation, no less important, was the increase in corrosion resistance compared to the uncoated steel The TiN films deposited showing (111) preferred orientation showed better corrosion resistance than films presenting other orientations.

Electrodeposition of composite coatings containing nanoparticles in a metal deposit

Abstract: Recent literature on the electrodeposition of metallic coatings containing nanosized particles is surveyed. The nanosized particles, suspended in the electrolyte by agitation and/or use of surfactants, can be codeposited with the metal. The inclusion of nanosized particles can give (i) an increased microhardness and corrosion resistance, (ii) modified growth to form a nanocrystalline metal deposit and (iii) a shift in the reduction potential of a metal ion. Many operating parameters influence the quantity of incorporated particles, including current density, bath agitation (or movement of work piece) and electrolyte composition. High incorporation rates of the dispersed particles have been achieved using (i) a high nanoparticle concentration in the electrolyte solution, (ii) smaller sized nanoparticles; (iii) a low concentration of electroactive species, (iv) ultrasonication during deposition and (v) pulsed current techniques. Compositional gradient coatings are possible having a controlled distribution of particles in the metal deposit and the theoretical models used to describe the phenomenon of particle codeposition within a metal deposit are critically considered.

Electrochemical methods in tribocorrosion: a critical appraisal

Abstract: Tribocorrosion is an irreversible transformation of a material resulting from simultaneous physico-chemical and mechanical surface interactions in a tribological contact. Electrochemical methods are well suited for the study of tribocorrosion phenomena because they allow one to simulate the corrosive effect of the environment by imposing a fixed potential. Furthermore, the measurement of the anodic current permits one to determine the amount of material removed by oxidation as opposed to mechanical wear. In the present paper, experimental and theoretical aspects of applying electrochemical methods in tribology are discussed and recent results obtained with passivating metals in the authors' laboratory are presented. The importance of controlling the mechanical parameters and the contact geometry is stressed, and it is shown that these parameters can significantly affect the electrochemical response of a tribocorrosion system.