Effects of Cyclic Heat Treatment on Microstructure and Mechanical Properties of 13%Cr-4%Ni Martensitic Stainless Steel

The present work investigates the effects of thermal cycling heat treatment (TCHT) on microstructure and mechanical properties of 13%Cr-4%Ni martensitic stainless steel (13-4MSS). As-received 13-4 MSS was subjected to three different thermal cycling schedules by using a thermo-mechanical simulator (Gleeble 3800). The evolved microstructures were studied at three cycles for each thermal cycling schedule with the help of optical, scanning electron microscopy, x-ray analysis, and transmission electron microscopy. Hardness and notched tensile tests were conducted to further characterize the as-received and processed specimens. This cyclic treatment raised the hardness to 413 HV (for TCHT at 950 °C) from 274 HV (for as-received). A 42% (for TCHT at 950 °C) and 39% (for TCHT at 1050 °C) hike in ultimate tensile strength (UTS) with a slight decline in ductility was observed as compared to the UTS and ductility of as-received steel. The evolved microstructure, dislocation density, and the refinement of martensitic blocks attributed to the enhanced hardness and UTS. The coarsening of laths (observed at 1050 °C) and bimodal lath structure (observed at 950 °C) were also found to control the mechanical properties of the present steel.