Journal of Emerging Trends in Engineering and Applied Sciences (JETEAS) 5(2):105110 (ISSN: 21417016) 105                            !"#   $  %"&  Facultad de Estudios SuperioresCuautitlán, Universidad Nacional Autónoma de México, CuautitlánIzcalli, C.P. 54740. Edo, México.  División Industrial, Universidad Tecnológica de Querétaro, Av. Pie de la Cuesta 2501. C.P. 76148. Querétaro, Qro. México.  Instituto Mexicano del Transporte, Carretera QuerétaroGalindo Km. 12, Pedro Escobedo, Qro. México.  División de Posgrado, Facultad de Informática, Universidad Autónoma de Querétaro, Ave. de las Ciencias S/N, C.P. 76230. Querétaro, Qro. México,  Departamento de Nanotecnología, Centro de Física Aplicada y Tecnología Avanzada, Universidad Nacional Autónoma de México, Campus Juriquilla, C.P. 76230. Querétaro, Qro. México. ’ ()*   +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ ,(&( Mechanical properties at the heat affected zone of welded Hadfield steel were studied as a result of different options of post cooling. Samples were postcooled in furnace, at room temperature and in mineral oil. The heat temperature, the cooling rate and the postcooling process affected the metallurgical microstructure, and consequently, mechanical properties as tensile strength, yield strength, strain and microhardness. Mechanical properties changed dramatically when welded Hadfield steel specimens were postcooled at different conditions. Discontinuities at the grain boundary of the heat affected zone normally weaken parts under stress or cyclic loads. Results were compared among three postcooling methods after welding and no welded samples in order to evaluate mechanical properties between the new Hadfield steel and pieces that were repaired by welding. According to the results, in terms of one manufacturing process, Hadfield steel parts are not recommendable to reduce the HAZ effect in neither case of postcooling conditions that were tested. The welding process produced heat retention, and consequently, metallurgical changes in detriment of the Hadfield steel mechanical properties. Mechanical properties showed significant differences among the different postcooling options of this study as a result of the metallurgical changes __________________________________________________________________________________________ -.* carbides, postcooling, fracture, Hadfield steel, mechanical properties, welding repair. /010/ The Hadfield steel is used in the heavy industrial component manufacturing such as mill hammers, oil derrick, and others. However, high impact applications are restricted both at room temperature and low temperature. Hadfield steel has a high superficial wear resistance in a metaltometal friction environment. It also has a good austenitic stability and an excellent transition temperature. These characteristics make this steel a good candidate to be hardened by heat treatment. This allows many applications in the mining industry, chemical industry, high wear environmental conditions and tear processes. However, the Hadfield steel chemical composition makes it difficult to be repaired by welding process because it can affect the mechanical properties detrimentally (Avery et al., 1992). Still, not much attention has been paid to failures in this Mn steel. Hardening of austenitic Mnsteel is obtained by the combination of a high Mn content and a rapid cooling from a high temperature. It is particularly useful for heavy duty applications involving both abrasion and heavy impact. However, it is not resistant to low stress abrasion (Diesburg and Borik, 1974). The typical chemical composition of Hadfield steel is: 1.0% to 1.4% wt C; 10% to 14% wt Mn, and 0.3% to 0.5% wt Si. Manganese is a weak carbideforming element; it does not react with iron contained in steel to form separate carbide; it partially dissolves in cementite where it replaces a part of the iron atoms (Fe, Mn) (Branislav et al., 2010). Mn increases the toughness and hardness, and affects adversely ductility and weldability (Bertold, 1993). The absence of carbides is a function of chemical composition, heat treatment and cross section (Maratray and Norman, 1961). The exceptional work Journal of Emerging Trends in Engineering and Applied Sciences (JETEAS) 5(2): 105110 © Scholarlink Research Institute Journals, 2014 (ISSN: 21417016) jeteas.scholarlinkresearch.org, jeteas.scholarlinkresearch.com