Double-step inter-critical tempering of a supermartensitic stainless steel: Evolution of hardness, microstructure and elemental partitioning

Autor(es)

Escobar, J. D. ^[1] ; Oliveira, J. P. ^[2] ; Salvador, C. A. F. ^[3] ; Tschiptschin, A. P. ^[1] ; Mei, P. R. ^[4] ; Ramirez, A. J. ^[5]

Afiliação do(s) autor(es)

^[1] Univ Sao Paulo, Met & Mat Engn Dept, Av Prof Mello Moraes 2463, BR-05508030 Sao Paulo, SP - Brazil

^[2] NOVA Univ Lisbon, NOVA Sch Sci & Technol, Dept Mech & Ind Engn, UNIDEMI, P-2829516 Caparica - Portugal

^[3] Univ Sao Paulo, Inst Phys, BR-05315970 Sao Paulo, SP - Brazil

^[4] Univ Campinas FEM Unicamp, Coll Mech Engn, BR-13083860 Campinas, SP - Brazil

^[5] Ohio State Univ, Dept Mat Sci & Engn, Welding Engn, 1248 Arthur E Adams Dr, Columbus, OH 43221 - USA

• Tipo de documento: Artigo Científico
• Fonte: MATERIALS CHARACTERIZATION; v. 158, DEC 2019.
• Citações Web of Science: 0

Resumo

The maximum allowed hardness for low carbon martensitic stainless steel components used in the oil and gas industry is 247 HV. Inter-critical tempering is an effective method for hardness control due to the production of stable reverted austenite. By conducting multiple-step tempering cycles, the austenite reversion kinetics can be accelerated and its thermal stability upon cooling can be greatly increased. In this work, supermartensitic stainless steel samples were subjected to two-step inter-critical tempering cycles. First, all samples were heat-treated at 625 degrees C for 2.5 h to minimize hardness through the maximization of stable austenite. Then, a second stage tempering with temperatures between 560 and 720 degrees C for 2.5 h was studied. The amount of stable reverted austenite at room temperature increased for second stage temperatures below 625 degrees C. Between 625 and 670 degrees C, the amount of reverted austenite notably increased at high temperature but it had limited thermal stability upon cooling. Above 670 degrees C, all newly reverted austenite was completely unstable during the cooling stage and partial dissolution of the stable austenite obtained after the first tempering cycle also occurred. Interestingly, hardness was mostly insensitive to the stabilization of additional austenite or to the newly formed fresh martensite. (AU)

• Processo FAPESP: 18/21251-5 - Caraterização do efeito de endurecimento secundário ativado por temperatura de aços resistentes ao fogo durante a simulação de incêndios
• Beneficiário: Julian David Escobar Atehortua
• Modalidade de apoio: Bolsas no Brasil - Pós-Doutorado
• Processo FAPESP: 16/13466-6 - Estudo correlativo por tomografia de sonda atômica e microscopia eletrônica de transmissão nas interfaces M/A, B/A e precipitados após tratamentos térmico in situ para aço inoxidável supermartensítico e aço avançado de alta resistência com efeito TRIP
• Beneficiário: Julian David Escobar Atehortua
• Modalidade de apoio: Bolsas no Exterior - Estágio de Pesquisa - Doutorado