Study of plasma nitriding and evaluation of fatigue life of 7075 - T651 aluminum alloy nitrided

Abstract

Most of structural components when in service are subjected to variable loads, so they are susceptible to fatigue process. Between 80% and 90% of the components, under variable stress, suffer fatigue fracture. The plasma nitriding is an alternative method of raising the surface hardness, fatigue resistance, wear resistance and corrosion resistance of alloys, improving the performance of the materials found. The 7075 aluminum alloy (AA7075) in the T6 condition is formed by a solid solution heat-treated and artificial aging. This alloy has reasonable resistance to stress corrosion in corrosive atmospheres, this resistance, as well as the mechanical properties of the alloy, is affected by a high density of intermetallic precipitates that are present, for this reason, it is very important to know their microstructural and mechanical characteristics. This work aims to study the plasma nitriding and the evaluation of fatigue life of 7075 - T6 aluminum alloy, in the T651 variation (with stress relieving) nitrided. It will be used the 7075 - T651 aluminum alloy, received in the form of cylindrical bars. The nitriding will be made on the 7075-T6 aluminum alloy in a PEN system of continuous discharge current. The chamber used for nitriding has a cylindrical form in stainless steel and a volume of 20 L. The high cycle fatigue tests will be conducted, in a fatigue machine of BALDWIN brand, in rotating bending conditions (R = -1), with constant amplitude load (CAL). It will be used 15 test specimens for determining the S-N curves for each condition (before and after nitriding) and for each level of stress applied will be made three replicas. Studies about fatigue life of 7075-T651 aluminum alloy after plasma nitriding are rare in the literature, although they are useful for various applications, especially for the aircraft sector. (AU)