The present work describes the influence of the parameters employed in the gas tungsten arc welding process (GTAW) when nickel powder is used as a filler metal in 2304/2507 duplex stainless-steel dissimilar joints. Multi-objective optimization was applied in order to maintain the austenite/ferrite percentage in the welded zone. A microstructural and phase quantification analysis was performed in each sample through optical and scanning electron microscopes. It was found that a nickel powder addition combined with low heat input increased the biphasic ratio across the different zones of the dissimilar welded samples. Although the austenite volume fraction increased in the 2304 heat-affected zone (HAZ) near to 25%, it was not sufficient according to international standards. The obtained results led to the maintenance of the 50/50 phase percentage in the 2507 HAZ welded joint side, as well as to the increment of the austenite percentage in the 2304 HAZ.

A study of surface hardening of Ductile Iron (DI) with and without austempering heat treatment was developed. The chemical composition of the material contains alloying elements such as Cu and Ni, that allow to obtain a Ductile Iron Grade 120-90-02, based on ASTM A536, which was heat treated to be transformed to Austempered Ductile Iron (ADI). Specimens of 10 × 10 × 5 mm³ were obtained for application of surface hardening by Nd:YAG UR laser of 150 W maximum power. The parameters used were advance speed of 0.2 and 0.3 mm/s and power at 105, 120, 135 and 144 W; the departure microstructures were fully pearlitic in the samples without heat treatment, and ausferrite for austempered samples. Microstructural characterization of hardened samples was performed were analyzed and martensite and undissolved carbides were identified in the pearlitic samples, while in ausferrite samples it was found finer martensite without carbides. The depth of hardened surface to different conditions and their respective microhardness were measured. The results indicate that the surface hardening via laser is a suitable method for improving wear resistance by means of hardness increment in critical areas without compromising the core ductility of DI components, but the surface ductility is enhanced when the DI is austempered before the laser hardening, by the reduction of surface microcracks.