Lower corrosion resistance of the nitrocarburized layer formed on two supermartensitic stainless steel types

Autor(es)

Cesar Augusto Duarte Rodrigues ^[1] ; Luiz Carlos Casteletti ^[2] ; Frederico Augusto Pires Fernandes ^[3] ; Carlos Alberto Picon ^[4] ; Germano Tremiliosi-Filho ^[5]

Afiliação do(s) autor(es)

^[1] Universidade de São Paulo - USP. Instituto de Química de São Carlos - Brasil

^[2] Universidade de São Paulo - USP. Departamento de Engenharia de Materiais e Manufatura - Brasil

^[3] Universidade Federal do ABC - UFABC. Centro de Engenharia, Modelagem e Ciências Sociais Aplicadas - Brasil

^[4] Universidade Estadual Paulista Julio de Mesquita Filho - UNESP. Campus de Ilha Solteira. Departamento de Física e Química - Brasil

^[5] Universidade de São Paulo - USP. Instituto de Química de São Carlos - Brasil

• Tipo de documento: Artigo Científico
• Fonte: REM, Int. Eng. J.; v. 77, n. 4 2024-09-06.

Resumo

Abstract The aim of this study was to verify the pitting corrosion behavior in the surface layers obtained by plasma nitrocarburizing at 400 and 450 °C/5 h on two types of super-martensitic stainless steel, namely micro-alloyed (Nb-SMSS) and unalloyed (SMSS). The results reveal that in all the nitrocarburized layers, a discontinuous, thin layer measuring less than 5µm in thickness exhibits a microhardness exceeding 950 HV0.05, for the two steels. Furthermore, the structure of the surface layer is a combination of expanded austenite (γN), expanded martensite (α`N), ε-Fe2-3N, cementite (θ-Fe3C), and traces of CrN. The surfaces exhibit poor corrosion resistance across all layers, which can be attributed to localized micro-galvanic corrosion between the iron nitride (ε-Fe2-3N) and expanded austenite (γN), since they are known to have higher corrosion resistance, as well as expanded martensite ((α`N) and cementite (θ-Fe3C), which have lower corrosion resistance. This corrosion process initiates after the dissolution of the surface layer in a 3.5% NaCl solution, subsequently leading to substrate corrosion. (AU)

• Processo FAPESP: 19/22183-6 - Electrocatálise VI: aspectos fundamentais e aplicados em problemas emergentes e clássicos em conversão eletroquímica de energia
• Beneficiário: Edson Antonio Ticianelli
• Modalidade de apoio: Auxílio à Pesquisa - Temático