Critical Pitting Temperature of Ti-6Al-4V Produced with Rapid Prototyping Technology: Electron Beam Melting Machine Abstract Titanium and its alloys are valuable engineering materials due to their excellent mechanical and physical properties. Comparing to other metallic materials such as stainless steel and Co-Cr alloys; Ti and its alloys are of lighter weight, higher strength-density ratio, superior corrosion resistance in wide range of environments, and better biocompatibility in human body. The most widely used titanium alloy is Ti-6Al-4V. It contains a combination of α stabilizer (Aluminum) and β stabilizer (Vanadium) that gives better microstructure combination, resulting in a good balance of strength, ductility, fracture and fatigue properties. Rapid prototyping technology allows the manufacturing of 3D intricate objects through the layer-by-layer technique. Electron beam melting (EBM) machine utilizes this 3D printing technology to fabricate complex objects using Ti-6Al-4V alloy. EBM machine uses electrons as the energy source to melt layer-by-layer the metallic powder and build the required parts under vacuum pressure of 10-3 mbar and temperature of 690°C. Parts produced with this machine can be used in many applications such as; petrochemical industry, chemical processing, aerospace applications, medical applications, and automotive industry. Due to the unique manufacturing conditions of high temperature, vacuum pressure, and quenching of the molten metal to nearly room temperature in just a few hours; the corrosion behavior of produced part is likely very different from that of traditional wrought alloys. In addition, surface roughness and density of parts out of such machine is different than traditional commercial titanium. Notwithstanding this, EBM machine can work under different sets of processing parameters, which allows a control of part properties. This study measures the critical pitting temperature (CPT) of samples produced under different processing parameters of EBM machine. CPT test was performed to detect the temperature at which the part will start to pit in a 3.5% weight NaCl solution. CPT gives an indication of the ability of the metal to withstand pitting under specified tested condition and specifies the temperature at which pitting of the surface will start. Surface roughness and density were measured as well, and a Minitab software was used to relate these properties to the EBM machine manufacturing parameters in order to optimize the best working parameters that will enhance the quality and increase corrosion resistance of produced parts.


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