Abstract
Internal cracks could be healed under the process of hot plastic deformation. In this study, mechanical properties recovery after crack healing in SA 508–3 steel were investigated. Microstructures of the crack healing zones were observed using an optical microscope (OM) and electron back scattered diffraction (EBSD) technology, and the recovery degrees of mechanical properties in the crack healing zones with the healing temperature and a reduction ratio were tested systematically. The results showed that the internal cracks in SA 508–3 steel disappeared and were replaced by newly formed grains, achieved by recrystallization and abnormal grain growth. The tensile properties of crack healing zones could be fully restored, while their impact and low cycle fatigue properties could only be partially achieved. The recovery degrees of mechanical properties in crack healing zones increased with increasing the healing temperature and reduction ratio in the temperature range of 950–1050 °C. When the temperature was above 1150 °C, the impact properties began to deteriorate because of grain coarsening and larger MA (martensite–austenite) constituents. The microstructural evolution of the crack zone in the SA 508–3 steel was sketched.
Highlights
During the manufacturing process of heavy forgings, cavity-type defects, such as cracks and voids, are inevitable
It was obtained by composition measurement that location 1 had a relatively high volume of chemical composition of O, which indicated the existence of nonmetallic inclusions, such as oxides
Hot plastic deformation was applied to internal crack healing in SA 508–3
Summary
During the manufacturing process of heavy forgings, cavity-type defects, such as cracks and voids, are inevitable. For the sake of serviceability and economic benefits, the strategy that internal crack in heavy forgings could be healed has attracted much attention. Based on the existing researches on crack healing in metallic materials, the healing methods mainly include electro pulsing treatment [2,3,4,5], heat treatment [6,7,8,9], and hot plastic deformation [10,11,12]. Considering the actual production requirements and economic efficiency, hot plastic deformation is the most efficient and most feasible method in the crack healing of heavy forgings
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