Solution Nitriding of Stainless Steels for Process Engineering

Abstract

Solution nitriding is a controlled heat treatment of stainless steels carried out at 1100 ± 50 °C in N2 gas. Depending on the alloy content a hard martensitic or a ductile austenitic high nitrogen case of about 2 mm in depth is formed, which reduces wear by sliding, fretting, erosion and cavitation. In contrast to carbon dissolved nitrogen does not impair the resistance to superimposed corrosion, so that solution nitriding is suitable for components subjected to the flow of aggressive fluids containing suspended particles which is often encountered in chemical and process engineering.

Metallic materials for tribocorrosion systems

“…By this, the surface hardness is increased from ~220 to 330 HV. The effect on sliding wear is about as high as for the autenitic steel (Berns et al 2000a). The pitting potential in NaCl is increased.…”

“…While at the temperatures of conventional nitriding, nitrogen gas N 2 does not react with steel surfaces, this changes at temperatures above 1000 °C (Berns et al 2000a). Here N 2 partly dissociates into N. At the metal surface, an equilibrium is established between the partial pressure of nitrogen at the outside and the nitrogen content of the surface.…”

“…In austenitic steels, the nitrogen addition leads to higher hardness and resistance to adhesion. The mass loss in a sliding wear test is reduced by 1-2 orders of magnitude compared to solution annealing (Berns et al 2000a). Because of increasing strength and strain hardening, cavitation resistance can also be increased.…”

“…Similar results can be achieved by the higher alloyed duplex steel G-X3CrNiMoCuN26-6-3-3. Field tests in the bypass of an flue gas desulphurisation (FGD) plant and in a sewage pump with considerable load of Cl -and SO 4 2-ions as well as quartz sand also revealed a considerable increase of lifetime of the solution nitrided compared to the solution annealed state (Berns et al 2000a). In nickel-martensitic steels, solution nitriding also leads to the formation of an austenitic case.…”

Efeito do nitrogênio na usinabilidade do aço inoxidável austenítico: uma avaliação utilizando a técnica da esclerometria pendular instrumentada

“…As rotas de produção dos aços de alto nitrogênio que utilizam metalurgia sob alta pressão, metalurgia do pó, e difusão no estado sólido vêm sendo intensamente estudadas [9][10][11]. Recentemente foi desenvolvido um tratamento termoquími-co de baixo custo, que permite aumentar o teor de nitrogênio na superfície dos aços [6,[11][12][13][14][15][16][17], chamado de Nitretação Gasosa em Alta Temperatura (NGAT). Esse tratamento é feito expondo o aço a atmosferas contendo N 2 em temperaturas entre 100 e 1200ºC.…”