Dissertation > Excellent graduate degree dissertation topics show

Corrosion Resistance of Nickel Free High Nitrogen Austenitic Stainless Steel

Author: JiangYuZhen
Tutor: JiChangTao
School: Changchun University of
Course: Materials Processing Engineering
Keywords: Nickel free high nitrogen austenitic stainless steel Microstructure Pitting Corrosion rate Polarization curve testing
CLC: TG142.71
Type: Master's thesis
Year: 2011
Downloads: 158
Quote: 0
Read: Download Dissertation

Abstract


Nickel free high nitrogen austenitic stainless steels keep high plasticity and toughness and without magnetic compared with the traditional austenitic stainless steels. But the strength improves obviously. At the same time they have excellent biocompatibility and corrosion resistance. They become the focus of competition and development in the world because they can save the precious resources of nickel and reduce the costs of production. At present, the production of nickel free high nitrogen austenitic stainless steels adopts high pressure metallurgy method in the world. This method has high production costs and high danger, so it is not suitable for mass production. Thus seeking a way of smelting nickel free high nitrogen austenitic stainless steels at atmospheric pressure is the key of material scientific research. The solubility of nitrogen in steels is very low at atmospheric pressure, so compared with high pressure metallurgy, there are lots of nitrogen porosities in the organization of high nitrogen austenitic stainless steels smelted at atmospheric pressure and the distribution of nitrogen is uneven. But the nitrogen porosities will be welded in subsequent rolling process. The distribution of nitrogen is uniform after solution treatment and the organization is full austenite. In this state, the tested steels smelted at atmospheric pressure have excellent corrosion resistance or not is the key of whether they can be applied in practice.In this paper, (Cr18Mn18Mo2NbN0.6) nickel free high nitrogen austenitic stainless steel smelted in an atmospheric pressure was studied. The microstructures of casting, rolling state and solid solution treatment state were analyzed through scanning electron microscope, optical microscope etc. Acid pickling and polarization curve testing of nickel free high nitrogen austenitic stainless steel after solid solution treatment and 1Cr18Ni9Ti were done in acidic medium (10%H2SO4 and 10%HNO3); Salt spray corrosion testing and polarization curve testing of tested steel after solid solution treatment and 1Cr18Ni9Ti were done in neutral medium (3.5%NaCl); The microstructure analysis, FeCl3 soak testing and polarization curve testing of tested steel after precipitation of nitrides, cold deformation 10%,20%,30%,40% and rolling state were done. The experimental results show that the cast structure of nickel free high nitrogen austenitic stainless steel was equiaxial dendritic crystals. Undissolved sheet nitrides and nitrogen porosities existed between dendritic crystals. The nitrogen porosities will be welded in subsequent rolling process. The microstructure of rolling state of tested steel was obvious layer structure. The matrix was austenite. Layer nitrides distributed on the interface of layer structure and between layers. The microstructure of the tested steel after solid solution treatment was full austenite. Lots of annealing twins existed in the microstructure. The grains of austenite were very small. The corrosion rate of nickel free high nitrogen austenitic stainless steel was less than 1Cr18Ni9Ti in 10%H2SO4 and 10%HNO3.The natural corrosion potential and pitting corrosion potential of nickel free high nitrogen austenitic stainless steel was higher, the passivation was very wide. This was because nitrogen improved corrosion resistance. The corrosion rate of nickel free high nitrogen austenitic stainless steel was less than 1Cr18Ni9Ti in 3.5%NaCl. 1Cr18Ni9Ti appeared serious intergranular corrosion while the surface of nickel free high nitrogen austenitic stainless steel only appeared a small amount of smaller pitting corrosion pits. The natural corrosion potential of nickel free high nitrogen austenitic stainless steel was higher and the current density of passivity was smaller. Therefore nickel free high nitrogen austenitic stainless steel had stronger ability of resisting Cl- corrosion than 1Cr18Ni9Ti. The natural corrosion potential and pitting corrosion potential of tested steel after different cold deformation approximately equal with rolling state. But when distortion was greater, the number of pitting corrosion pits increased, and pitting corrosion pits deepen. The pitting corrosion potential of tested steel after precipitation of nitrides obviously reduced and the pitting corrosion pits appeared vastly.

Related Dissertations

  1. Research on Technology and Mechanism of Joining Cemented Carbide to Carbon Steel,TG454
  2. Research on Processings and Microstructure and Properties of HRB400MPa,TG335
  3. Heat Treatment of Cast Al-Cu-Ti-(La) alloy microstructure and mechanical properties of,TG166.3
  4. ECAP for Mg-Zn-Zr-Gd alloy fatigue behavior of,TG379
  5. Al-Si-Cu-Nd cast aluminum alloy microstructure and fatigue properties,TG136.1
  6. Study on the Preparation and Doping Y2O3 of Low-voltage ZnO Varistor Ceramics,TN304.93
  7. Effect of the Rubbing and Wearing Behavior of Steel Rail by Ultrasonic Peening,TG115.58
  8. Plasma Spraying Nano ceramic coating microstructure and properties of,TG174.442
  9. Reactive Hot-Pressing and Mechanical Properties of （ZrB2-ZrO2）/BN Composites,TB332
  10. A Study on Microstructure and the Wear Resistant of Laser Cladding Ni/WC Composite Coating,TG174.44
  11. Study on the Technics Structure and Performance of Compound Processing of Gas Multi-Elements Peneterting and Electroless Plating,TG156.8
  12. Microstructure and Property of Nano Ni-P-Al2O3 Electroless Plating Layer Treated by Laser Technology,TG174.4
  13. Microstructure and Mecha Nical Properties of Dispersion Strengthening 20 Steel by TiO2 Particles,TG142.1
  14. Preparation and Microstructure of Nano-crystalline Zn-Ni Alloy by Jet Electrodeposition,TG174.4
  15. Microstructure and Property of Friction Stir Welding Jiont for High Strength Aluminumalloy Under Controlled Cooling Condition,TG407
  16. Technology Study and Accuracy Analysis of Optical Microstructures Manufactured by Fast Tool Servo,TG51
  17. Study on Laser Cladding Nickel Based Alloy and Nano-composite Coatings,TG174.4
  18. Research on Squeeze Casting Technology for High Strength and Toughness Aluminum Alloy Parts,TG249.2
  19. The Microstructure Transformation and Life Analysis of T91/P91 Steel at Elevated Temperature,TG142.15
  20. Study on Technology of Laser-Arc Hybrid Welding for LY12 Aluminum Alloy,TG456.7
  21. Study on the Mg-Si Alloys Prepared with the Fine Si Powders as the Raw Material,TG339

CLC: > Industrial Technology > Metallurgy and Metal Craft > Metallurgy and Heat Treatment > Metallic materials > Steel > Special performance of steels > Stainless steel, acid-resistant steel
© 2012 www.DissertationTopic.Net  Mobile