The thermal cycle control of heat treatments for the quenching and tempering of martensitic stainless steels, type 13Cr5Ni0,02C, is essential for obtaining the good mechanical resistance which is associated to corrosion resistance, mainly in equipment used in petroleum extraction. Samples were austenized during three hours at 1025°C, with posterior air and water quenching and tempering at 680ºC during 10 hours and then, air-cooled. A second sample group was heat treated under the same conditions, but a stress relief was done at 150ºC for 1 hour and then, air-cooled. The tempering increases substantially its hardness and ductility and in some cases, without substantial reduction of the mechanical resistance. The great hardness and resistance of the tempered martensite is related to the large area relation between the cementite and matrix contours, because these act as barriers to the dislocation motion during the plastic deformation. In this way, the matrix which is ductile is reinforced by the cementite.
Heat treatment; martensitic stainless steels; mechanical properties
