Microstructure and Properties of Porous High-N Ni-Free Austenitic Stainless Steel Fabricated by Powder Metallurgical Route.

Ling Hu,Zhengwu Peng,Hanlin Peng,Tungwai Ngai,Liejun Li,Feng Zhou

doi:10.3390/ma11071058

Abstract

Porous high-N Ni-free austenitic stainless steel was fabricated by a powder metallurgical route. The microstructure and properties of the prepared porous austenitic stainless steel were studied. Results reveal that the duplex stainless steel transforms into austenitic stainless steel after nitridation sintering for 2 h. The prepared high-N stainless steel consists of γ-Fe matrix and FCC structured CrN. Worm-shaped and granular-shaped CrN precipitates were observed in the prepared materials. The orientation relationship between CrN and austenite matrix is [011]CrN//[011]γ and (-1-11)CrN//(1-11)γ. Results show that the as-fabricated porous high-nitrogen austenitic stainless steel features a higher mechanical property than common stainless steel foam. Both compressive strength and Young’s modulus decrease with an increase in porosity. The 3D morphology of the prepared porous materials presents good pore connectivity. The prepared porous high-N Ni-free austenitic stainless steel has superior pore connectivity, a good combination of compressive strength and ductility, and low elastic modulus, which makes this porous high-N Ni-free austenitic stainless steel very attractive for metal foam applications.

Highlights

Metal foams have attracted much attention due to their unique combination of properties: high specific strength, low density, low elastic modulus, lightweight and high energy absorption capacity [1]
The inner porous morphology can be built up layer by layer using X-ray 3D diffraction with a high resolution of 2 μm
The elastic modulus decreases to approximately 40 GPa when the amount of space holder increases to 30 wt. %

Summary

Introduction

Metal foams have attracted much attention due to their unique combination of properties: high specific strength, low density, low elastic modulus, lightweight and high energy absorption capacity [1]. They can be used in numerous applications, such as lightweight constituents, filters, biomedical implant materials, vibration dampers and heat exchangers [2]. Stainless steel foams have been made through several methods, and the microstructure, mechanical properties and corrosion resistance have been researched [1,2,5,6,7], showing good potential to be a good alternative for metal foams in applications that require lightweight, excellent mechanical properties and good corrosion resistance. The idea of fabricating HNASS foam could open up new potential

Results

Discussion

Conclusion