It has been known that the ferritic stainless steel can be changed to martensitic stainless steel when nitrogen is added. However the high hardness of martensitic stainless steel prevents the plastic deformation, In this study, in stead of martensite, the surface microstructure was changed into nitrogen pealite to increase the plastic deformation easily by isothermal heat treatment after high temperature gas nitriding (HTGN) the AISI 430 ferritic stainless steel. The Isothermal treatment was carried out at 780 ℃ for 4, 6, and l0hrs, respectively, after HTGN treatment at 1100 ℃ 10 hrs. The surface layer of isothermal-treated steel appeared nitrogen pearlite with fine chromium nitride in the matrix of ferrite. Hence, the interior region that was not affected by nitrogen permeation exhibited ferrite phase. When quenching the isothermal treated steel at 1100℃, martensitic phase formed at the surface layer. The hardness of surface layer of isothermal-treated steel and quenched steel measured the value of 150～240Hv and 630Hv, respectively.
Sang-Jun Park Jung-Hyun Kong Han-Yung On Jee-Hyun Sung Chang-Yong Kang Jang-Hyun Sung
Department of Materials Science and Engineering,Dong-A University,840 Hadan-ong,Saha-gu,Busan 604-71 Department of Materials Science and Engineering,Dong-A University,840 Hadan-Dong,Saha-gu,Busan 604-7 Daegu Machinery Institute of Components and aterials,12,Horim-dong,Dalseo-gu,Daegu,Korea Division of Materials Science and Engineering,Pukyong National University, Busan,Korea Center for Advanced Net Shape Manufacturing and Clean Process,Dong-A University,840 Hadan-dong,Saha-