Traitements mécaniques et thermomécaniques de surfaces d'aciers austénitiques et effet induit sur la nitruration lors des traitements Duplex

Abstract : Optimizing the surface microstructure and properties is very important to obtain high performance behaviour. Applying appropriate mechanical and thermochemical treatments has been the prime objective of metallurgists. More recently, and particularly for the stainless steels, the Plasma Nitriding was found to be an efficient technique for enhancing the hardness and wear resistance. However, as the nitriding temperature is about 500 °C, the formation of nitrides on the surface leads to a decrease of the corrosion resistance of these alloys. Recent works have shown that using a mechanical pre-treatment allows to decrease the treatment temperature and duration, and also to enhance the nitrogen diffusion within the stainless steels surfaces. In the present work, performances of different Duplex treatments (mechanical + thermochemical) are studied. The Surface Mechanical Attrition Treatment (SMAT), cold rolling and the High Current Pulsed Electron Beam (HCPEB) are used as surface activators prior to plasma nitriding of stainless steels. Before studying the effect of surface activation on the nitrogen diffusion, the effect of the different SMAT parameters (balls size, balls nature, treatment duration … etc.) on the microstructure is analysed. A new technique based on the notion of Geometrically Necessary Dislocations (GND) is used to depict the thickness of the different SMAT-induced layers and compare the effect of the processing parameters. Then, comparative analysis of the results obtained after nitriding of mechanically deformed samples leads to quantify the effect of the different Duplex treatments. X-Ray Diffraction, Secondary Electron Microscopy associated with Electron BackScattered Diffraction (EBSD), hardness measurement and chemical composition analysis by Glow Discharge Optical Emission Spectroscopy (GD-OES) showed the importance of the surface microstructure and deformation state on the nitrogen diffusion
Document type :
Theses
Complete list of metadatas

Cited literature [55 references]  Display  Hide  Download

https://hal.univ-lorraine.fr/tel-01750818
Contributor : Thèses Ul <>
Submitted on : Tuesday, July 16, 2019 - 4:20:52 PM
Last modification on : Tuesday, July 16, 2019 - 4:22:05 PM

File

DDOC_T_2014_0100_SAMIH.pdf
Files produced by the author(s)

Identifiers

  • HAL Id : tel-01750818, version 1

Citation

Youssef Samih. Traitements mécaniques et thermomécaniques de surfaces d'aciers austénitiques et effet induit sur la nitruration lors des traitements Duplex. Other. Université de Lorraine, 2014. English. ⟨NNT : 2014LORR0100⟩. ⟨tel-01750818⟩

Share

Metrics

Record views

115

Files downloads

32