| 13%Cr martensitic stainless steel was alloyed with 2∼6%Ni and 2%Mo, and impact properties and hardness have been tested after austenitizing and tempering treatment. Ni addition decreased austenitization (A_s, A_f) and martensitic transformation temperature(M_s). The steels with Ni showed high hardness after tempering treatment at the temperature up to 500℃, and decreased drastically after tempering at 600℃, which was caused by the decomposition of martensitic structure and the decrease of high dislocation density. After tempering at 700℃ the hardness of steels with 4-6% Ni content increased again, because martensite phase was transformed from austenite phase, which was formed during tempering. Ni addition enhanced impact energy of tempered steels. The steels with Ni content more than 4% did not show any tempered embrittlement, while the steels with 2%Ni showed a remarkable tempered embrittlement phenomenon after tempering at 500℃. |
|
