"Improvement in mechanical properties of 13 Cr Martensitic Stainless Steels using modified heat treatments"

13% Cr-0.2%C has very good combination of strength, corrosion resistance and impact toughness at sub-zero temperature for use in application such as oil and gas industry for tubing and piping applications. Compared with a 0.1%C-12%Cr steel, the 13%Cr steel has poor toughness due to enhanced %C and lack of carbide formers such as Mo and toughening alloying such as Ni. Hardening and tempering of thick samples have to be carried out in a suitable manner to achieve higher toughness. A modified heat treatment involving double quenching and tempering treatment resulted in a significant change in mechanical properties especially toughness. A comparison is made between the conventional hardening and tempering with modified process. The second hardening treatment was carried out at lower austenitising temperature compared to the first hardening resulting in fine microstructure complete free from necklace carbides and delta ferrite. Optical and SEM microstructures were correlated with mechanical properties obtained.