At global level, there is a continuing concern for the research and development of alloys for medical and biomedical applications. Metallic biomaterials are used in various applications of the most important medical fields like orthopedic, dental and cardiovascular. The main metallic biomaterials used in human body are stainless steels, Co-based alloys and Ti-based alloys. Titanium and its alloys are of greater interest in medical applications because they exhibit characteristics required for implant materials, namely, good mechanical properties (less elasticity modulus than stainless steel or CoCr alloys, fatigue strength, high corrosion resistance), high biocompatibility. The aim of this review is to describe and compare the main characteristics (mechanical properties, corrosion resistance and biocompatibility) for latest research of nontoxic Ti alloys biomaterials used for medical field.

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Plasma nitriding has significant advantages: very low running costs (reduced consumption of energy and gases); optimized structure and layers; and nitriding of stainless steels. Plasma nitriding is totally safe and has no poisonous gas emissions and no negative environmental impact. However, conventional plasma nitriding has a number of well-known difficulties, including the direct application of plasma on the parts to be treated, the risk of arcing, hollow cathodes, white layers, non-homogenous batch temperature and the impossibility to mix parts of different geometries in the chamber made this technology to be almost forgotten. In the last years, due to the ecofriendly character of the technology, several atempts were made in order to establish an improvement in this technique in terms of batch damages. Active screen plasma nitriding technology is a new industrial solution that enjoys all the advantages of traditional plasma nitriding but does not have its inconveniences. A comparative study regarding quality surface and formed layer properties between conventional plasma nitriding and active screen plasma nitriding was conducted, in order to highlight the advantages that comes with this relatively new technique.

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The aim of this paper is to analyze the corrosion process that occurs in galvanic couplings of different alloys. The study focuses on materials that can come into contact in submersible pumps used by water treatment plants. Because, the rotor, one of the pump main components must possess high chemical and mechanical properties, nodular cast iron is usually used. Therefore, this is exposed in the same environment with different types of materials, such as aluminum, copper, bronze, grey cast iron, low alloy steel or stainless steel from which other components are made. The tests have been performed in three types of residual waters with neutral, acidic and basic pH. According to this study, the nodular cast iron galvanic corrosion resistance is highly improved by the phosphate layer deposited on its surface.