Surface Properties of 316L Austenitic Steel Improved by Simultaneous Diffusion of Titanium and Aluminium

Britchi, Iulia Mirela; Ene, Niculae; Olteanu, M; Vasile, Eugeniu; Niţă, P.; Alexandrescu, E.

doi:10.4028/www.scientific.net/ddf.297-301.1

Cited by 6 publications

(5 citation statements)

References 18 publications

(17 reference statements)

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“…Woven samples, cut to a length of 72 mm, a width of 12 mm, and a thickness of 3.5 mm (corresponding to 11 wire layers), were buried in a pack mixture consisting of 57 wt.% Al 2 O 3 powders (20-50 lm particle size) as filler, 30 wt.% Ti powders (99.5% purity, À325 mesh) and 10 wt.% Raney Ni precursor powders (Ni-50 wt.% Al, 150 lm particle size) as sources, and 3 wt.% NH 4 Cl powders (100 lm particle size) as activator, with all powders procured from Alfa Aesar. At elevated temperature, the activator decomposes and reacts with the source powders to create a mixture of titanium and aluminum chloride gas, which subsequently deposits the metallic atoms onto the substrate [18,19]. Approximately 40 g of pack was poured in a steel retort, where the internal pressure rises at elevated temperatures, and the cut specimen was placed at the center of the retort.…”

Section: Introductionmentioning

confidence: 99%

Transient liquid-phase bonded 3D woven Ni-based superalloys

Erdeniz

Sharp²,

Dunand

2015

Scripta Materialia

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a b s t r a c tArchitectured Ni-based superalloy scaffolds were fabricated by three-dimensional weaving of ductile Ni20Cr (wt.%) wires followed by gas-phase alloying with aluminum and titanium via pack cementation. Bonding of neighboring wires occurs at necks that are formed by solid-state diffusion or by formation of a transient-liquid phase. Three-point bending tests of the superalloy weaves, after homogenization and aging to achieve a c/c 0 structure, show that, as bonding between wires increases, the materials withstand higher stresses and strains before onset of damage.Architectured cellular materials [1][2][3][4][5][6][7][8], such as honeycombs [4], trusses [5], and wire-based structures [6][7][8], offer a combination of low density and high specific strength, stiffness, permeability, and surface area. These materials have periodic structures that can be designed by using topological optimization models to enhance the desired properties [9-11]. One example is 3D woven metal structures, fabricated from Cu or Ni-Cr wires, that are topologically optimized to provide improved permeability in preferred directions with minimal loss in stiffness for thermo-structural applications [8]. Such cellular materials are of interest for extreme environments, since increased permeability allows for active cooling and results in prolonged service life, or even enables material use, at elevated service temperatures and stresses. A number of studies have been published in the area of periodic cellular nickel-based superalloys, none, however, using topological optimization tools [12][13][14]. The main reason for the limited number of existing studies is the difficulty in the processing of such superalloy architectured structures. Particularly, processing of wire-based structures are very challenging due to three manufacturing obstacles: (i) superalloy wires, especially below 500 lm diameter, are difficult to draw, and hence not widely available through suppliers, (ii) if drawn, they are not sufficiently ductile to withstand the bending angles required for weaving, and (iii) if woven, the contact points must be bonded to reach the full potential of mechanical properties, which is difficult due to the presence of oxide layers at the wire surface and low diffusivity, limiting the extent of solid-state bonding.In a recent study, we reported the fabrication of topologically optimized Ni-Cr-Al superalloy structures produced using 3D textile processes [7,8]. Ni-20Cr (all compositions are given in wt.% hereafter) wires were 3D woven or 3D braided, taking advantage of the room-temperature ductility of these wires, and subsequently aluminized via pack cementation [7], a chemical vapor deposition process that has been widely used to create aluminide coatings on Ni-based superalloys for corrosion protection [15][16][17]. Aluminized 3D woven structures were then homogenized into Ni-Cr-Al alloys and aged for the precipitation of c 0 particles, which are responsible for the high temperature creep resistance of superalloys. Simultaneously, the...

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Section: Introductionmentioning

confidence: 99%

Transient liquid-phase bonded 3D woven Ni-based superalloys

Erdeniz

Sharp²,

Dunand

2015

Scripta Materialia

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“…In the case of alumino-titanized samples, Ti 3 NiAl 2 N compound was determined in both, outer and inner layers with a higher concentration in the outer layer [11]. The difference between the microhardnesses in the inner layer and the metallic substrate is well evidenced in the optical micrograph, Figure 10.…”

Section: Defect and Diffusion Forum Vols 312-315mentioning

confidence: 88%

“…The sample cooling after diffusion was done slowly in the furnace down to the room temperature. The working conditions and sample preparation for investigations after thermo-chemical treatment are detailed in two previously published papers [10,11].…”

Section: Methodsmentioning

confidence: 99%

“…5, show the differences between the distributions of Ti, Ni, Fe, Cr, N and Al. The outer layers were analyzed and discussed in our previous papers [10,11]. The layers obtained by either diffusion with reaction of titanium or simultaneous diffusion with reaction of titanium and aluminium have hardneses higher than that of the metallic substrate, 316L austenitic steel, Table 4.…”

Section: Defect and Diffusion Forum Vols 312-315mentioning

confidence: 99%

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Diffusion Layers with Ti and Ti+Al Formed on 316L Austenitic Steel by a Pack Cementation Procedure

Britchi

Olteanu

Ene

et al. 2011

DDF

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Pack cementation procedure implies the use of a powder mixture containing the diffusive elements, which in our case are either Ti or Ti+Al, Al2O3 and NHCl as activator. In the case of titanizing the powder mixture contained 77% in weight Ti, while for alumino-titanizing Al/Ti = 1/5 ratio was employed. NH4Cl content was 3% in weight in all cases. Aluminium additions to the powder mixtures led to a decrease of the process temperature. Activation energy for the aluminizing of austenitic 316L steel is 73.87 KJ/mol, much smaller than for the titanizing, 257.86 KJ/mol. Activation energy for alumino-titanizing, in the same conditions, is 146.01 KJ/mol. All diffusion coatings, in the Ti – 316L and Ti+Al – 316L couples are formed of two layers having different structures and compositions. All couples were investigated by optical microscopy, electron microscopy (SEM and EDX), X-ray diffraction and microhardness trials.

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“…Prior to obtaining the enamelled layers, samples were thermochemically treated by titanizing by pack cementation procedure. The pack cementation procedure with obtaining of Ti diffusion coatings was described in detail elsewhere [22][23][24]. This procedure consists in packing 316L austenitic stainless steel samples in a powder mixture.…”

Section: Modification Of the Surface Of 316l Austenitic Stainless Ste...mentioning

confidence: 99%

Biovitroceramic Coatings on Modified Surface of 316L Austenitic Stainless Steel

Britchi

Olteanu

Ene

et al. 2012

JBBTE

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Austenitic stainless steel 316L is widely used in implantology due to its biocompatibility, a lower price than titanium and because can be easily mechanically machined. The drawback is due to the fact that toxic nickel and chromium ions are released into human body fluids. Our proposal is to coat 316L austenitic stainless steel with biovitroceramic layers made of oxide system SiO2, B2O3, Na2O, CaO, TiO2, P2O5, K2O, Li2O and MgO by means of an enamelling procedure in order to hinder the release of Ni and Cr ions from the metallic implant surface toward the tissue around the implant. In order to achieve a firm adherence of biovitroceramic layer onto the metal, with an optimal composition for biocompatibility and bioactivity, we have modified the steel surface by a titanizing thermochemical treatment. The adherence of the biovitroceramic layer to the 316L stainless steel with modified surface is very good. The biovitroceramic coating - metallic substrate couple was studied by optical microscopy, electron microscopy (SEM and EDAX), X-ray diffraction analysis and microhardness trials.

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Surface Properties of 316L Austenitic Steel Improved by Simultaneous Diffusion of Titanium and Aluminium

Cited by 6 publications

References 18 publications

Transient liquid-phase bonded 3D woven Ni-based superalloys

Transient liquid-phase bonded 3D woven Ni-based superalloys

Diffusion Layers with Ti and Ti+Al Formed on 316L Austenitic Steel by a Pack Cementation Procedure

Biovitroceramic Coatings on Modified Surface of 316L Austenitic Stainless Steel

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