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

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.

Notch (In)Sensitivity of Aluminum Matrix Syntactic Foams

“…This structure leads to higher relative density (~0.5) foams exhibiting outstanding compressive properties compared at least to the “conventional” open and/or closed cell metallic foams. MMSFs can be produced from any kind of metal in theory, but Al alloys are the most common [ 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 ], but Mg [ 11 , 12 , 13 , 14 , 15 , 16 , 17 ], Fe [ 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 ], Ti [ 26 , 27 , 28 , 29 ], and even Zn [ 30 , 31 , 32 , 33 ]-based MMSFs can also be found in the literature. The filler material can also be various ranging from mixed oxide ceramics [ 15 , 34 , 35 , 36 , 37 , 38 , 39 , 40 ] to high purity and quality alumina [ 41 , 42 , 43 , 44 ] or silicon carbide [ 2 , 10 , 12 ].…”

Microstructure, Mechanical, and Corrosion Properties of Ni-Free Austenitic Stainless Steel Prepared by Mechanical Alloying and HIPping

“…This can cause premature abrupt fracture of the material, and/or release harmful products of the corrosion into the human body. The essential problem is a negative charge of the alloying ions, especially of the toxic nickel, that can be released from the steel during implantation [5,6].…”

“…Because of these mentioned problems, high manganese–nitrogen (nickel-free) stainless steel is a material to replace older generations of the austenitic stainless steels. Investigations of the influence of nitrogen on steel properties have been carried out by many authors [1,6,7,8,9]. Nitrogen in a solid solution of a steel increases the strength and improves resistance to pitting and crevice corrosion in a water solution of chloride ions [1,7].…”

Application of Aluminium Flakes in Fabrication of Open-Cell Aluminium Foams by Space Holder Method

“…During powder processing with space holder particles, porosity can be introduced by adding an additional phase (space holder particles) to the metal powder to retain spaces in the material, which can be removed afterwards by chemical or thermal (during sintering) means [17,18,19,20,21]. The shape of the space holder particles controls the pore morphology of the pore structure.…”

“…For fabrication of open-cell topology metal foams, the main manufacturing processes are: Vapor phase deposition or electro-deposition of metal into a polymer foam precursor, infiltration of a preform, use of molten metal on a replaceable precursor, and powder processing with space holder particles. During powder processing with space holder particles, porosity can be introduced by adding an additional phase (space holder particles) to the metal powder to retain spaces in the material, which can be removed afterwards by chemical or thermal (during sintering) means [ 17 , 18 , 19 , 20 , 21 ]. The shape of the space holder particles controls the pore morphology of the pore structure.…”