P. Merino

A New Approach to the Determination of the Cathodic Protection Period in Zinc-Rich Paints

Abstract The present study examined the behavior of zinc-rich paints (ZRP) based on an epoxy binder in 3% sodium chloride (NaCl) solution. The study focused on the effect of some design parameters ...

Electrochemical Impedance Spectroscopy Study of the Corrosion Process on Coated Galvanized Steel in a Salt Spray Fog Chamber

Abstract The behavior of three different paint systems was investigated using the electrochemical impedance spectroscopy (EIS) technique. The coatings, based on chlorinated rubber, alkyd resin, and...

Microstructural characterization of laser surface melted AISI M2 tool steel

We describe the microstructure of Nd:YAG continuous wave laser surface melted high‐speed steel, namely AISI M2, treated with different laser scanning speeds and beam diameters on its surface. Microstructural characterization of the remelted surface layer was performed using light optical and scanning electron microscopy and X‐ray diffraction. The combination of the three techniques provided new insights into the substantial changes induced by laser surface melting of the steel surface layer. The advantage of the method is that it avoids the difficult and tedious work of preparing samples of this hard material for transmission electron microscopy, which is the technique normally used to study these fine microstructures. A melted zone with a dendritic structure and a partially melted zone with a heterogeneous cellular structure were observed. M2C carbides with different morphologies were identified in the resolidified surface layer after laser melting.

Modification of AISI M2 high-speed tool steels after laser-surface melting under different operating conditions

We applied a laser-surface melting treatment to AISI M2 high-speed steel – hardened and tempered – and studied the resulting surface characteristics (microstructure) and mechanical behaviour (hardness and wear performance). The steel was treated using a Nd:YAG continuous-wave laser with different operation conditions. The influence of the laser processing parameters on the individual beads and on the characteristics of the molten surface layer obtained using the multipass system with 50% overlap was studied. The microstructure characterization for all conditions is formed of MC- and M2C-type carbides, martensite, and retained austenite; the quantities of this phase depend on the operating conditions. It has been determined that low levels of power density and high scanning speeds of the beam lead to greater homogeneity in the microstructure with high hardness values and wear resistance.

Effect of Deep Cryogenic Treatment on the Microstructure of an Aerospace Aluminum Alloy

This paper describes how deep cryogenic treatment at 98K produces changes in the microstructure of a heat-treated aluminum alloy. It was observed how the sub-micrometric particles increased near and at the grain boundaries. This slight precipitation did not produce any modification in static mechanical properties. However, the compressive residual stresses of the material were higher after compared to before the treatment. Both these effects can enhance the life of this alloy through cryogenic treatment.

An Insight on the Influence of Ion Implantation on the Pitting Corrosion Resistance of AISI 430 Stainless Steel

Research on the effect of ion implantation on the corrosion behaviour of metals has been carried out for years, but some difficulties arise in the comparison of the obtained results due to variations in experimental conditions (alloys, surface preparation, doses, experimental techniques...). This work tries to overcome those differences, presenting the effect of several elements (Ce+, N+, Cr+ and Cr+ N+) implanted in similar conditions on the pitting corrosion resistance of AISI 430 stainless steel. Potentiodynamic measurements in 1M NaCl demonstrate the beneficial effect of all the implanted elements, showing that Ce+ is the less efficient ion, while Cr+ N+ co-implantation gives the best results in terms of localized attack resistance. Pitting morphology is explained in terms of the XPS and GIXRD data that allow chemical and structural characterization of the implanted layer. Those results help to enlighten the protection mechanisms involved in the considered implantations.

Optimization of Ageing Parameters of a Low Nickel Maraging Steel

In the present work the age hardening parameters of a 14Ni (200) maraging steel are studied in order to optimize mechanical properties of the steel. The initial characterization of the as received solution annealed steel has been carried out by optical and scanning electron microscopy (LOM and SEM), and hardness measurements. To identify the structural changes during ageing, differential scanning calorimetry (DSC) tests were performed. Different time-temperature combinations were considered for the precipitation hardening treatment of as-quenched material samples. After hardness measurements, three of these treatments were selected for an in depth study. The obtained microstructure at the maximum hardness peaks then analysed (LOM, SEM and TEM) and mechanical behaviour (strength, toughness and wear resistance) was studied for the final selection of the age hardening conditions.

Corrosivity of the N.W. Spanish sea water

Abstract The corrosivity of the Galician coast water is studied by the coulombstatic method, which is particularly appropriate to this sort of marine system. Samples taken at different depths in areas of Galician coast were analysed using low carbon steel as the metal of study. The obtained results show that these waters present a moderate level of corrosion (between 0.1 and O.S mm.year−1 penetration) compared to other data quoted in the literature. It is also observed that the corrosion rate decreases quickly with the depth as far as 1, 200 m, and diminishes less quickly at further depths.

Analysis of the Passive Layer Developed on Two Stainless Steels Co-Implanted with Chromium and Nitrogen

Surface analysis techniques (XPS and grazing incidence X-ray diffraction GIXRD) and electrochemical techniques have been combined to elucidate the effect resulting from Cr+ and N+ co-implantation in the formation and evolution of passive layers generated on two different stainless steels (AISI 430 and AISI 304L) in alkaline medium. The results show that the nitrides formed on AISI 430, identified as (Cr,Fe)2N1-x, are less resistant to dissolution while the nitride phase formed in AISI 304L, NCr with nanocrystalline structure, allows the compact growth of the oxide film.