scholarly journals Rotary bending as a mean for improving micro-cleanliness of stainless steels for high demanding applications

2018 ◽  
Vol 165 ◽  
pp. 20009
Author(s):  
Thomas Sourisseau ◽  
Dominique Ferrière ◽  
Frédéric Moser ◽  
Maximilien Libert ◽  
Pierre Chemelle ◽  
...  
Keyword(s):  
Thermal Expansion ◽  
Stainless Steels ◽  
Endurance Limit ◽  
Maximum Size ◽  
Medical Applications ◽  
Bending Tests ◽  
Oxide Inclusions ◽  
High Fatigue ◽  
Lower Thermal Expansion ◽  
High Level

Stainless steels are used for automotive or medical applications which require a high fatigue resistance correlated to a high level of micro-cleanliness. A methodology based on rotary bending tests carried out on wires or bars has been defined to determine the material’s endurance limit (after 100 millions cycles) and identify the largest subcutaneous inclusions or precipitates where failures initiate. This methodology has been applied to EN 1.4568 spring wires. Failures were found to initiate both at oxide inclusions and AlN precipitates. For the same size, AlN precipitates were observed to be more critical towards crack initiation than oxide inclusions, due to their angular shape and lower thermal expansion at high temperatures. However, oxide inclusions larger than the AlN maximum size strongly impact the material’s fatigue limit, and their density and size should be reduced.

Reduction in Wear Rate of α-Alumina and Silicon Nitride by Diffusional Surface Modification

1988 ◽  
Vol 140 ◽  
Author(s):  
A.K. Gangopadhyay ◽  
M.E. Fine ◽  
H.S. Cheng
Keyword(s):  
Wear Resistance ◽  
Thermal Expansion ◽  
Surface Modification ◽  
Silicon Nitride ◽  
Thermal Expansion Coefficient ◽  
Expansion Coefficient ◽  
Surface Region ◽  
Lattice Parameter ◽  
Lower Thermal Expansion ◽  
Wear Modes

AbstractThe surface regions of α-alumina and hot pressed silicon nitride were modified by suitable alloying in order to improve their wear resistance. The surface modification in polycrystalline α-alumina was done by diffusing chromia into the surface region which resulted in the formation of a thin layer of A12O3 - Cr9O3 solid solution which has a lower thermal expansion coefficient than pure α-alumina. Also Cr2O3 has a larger lattice parameter than α-alumina thus during cooling the surface was put into compression. The surface region of hot pressed silicon nitride was modified by diffusing α-alumina into the surface which resulted in the formation of a thin sialon layer. A surface compressive stress was again introduced due to the lower thermal expansion coefficient and larger latticeparameter of sialon compared to silicon nitride.Wear tests were conducted against 52100 steel under both lubricated and unlubricated sliding contact using a block on ring apparatus. The wear resistance of chromia surface alloyed α-alumina was improved considerably over unalloyed α-alumina under both lubricated and unlubricated conditions. The wear resistance of alumina surface alloyed silicon nitride was also improved over unalloyed silicon nitride under both lubricated and unlubricated conditions.Different wear modes were identified by examining the worn surfaces under the scanning electron microscope.

scholarly journals Study on Oxide Inclusions in 18-8 Stainless Steels

1969 ◽  
Vol 55 (14) ◽  
pp. 1329-1341 ◽  
Author(s):  
Tetsuya SAITO ◽  
Iku UCHIYAMA ◽  
Toru ARAKI
Keyword(s):  
Stainless Steels ◽  
Oxide Inclusions

High fatigue endurance limit of a Ti-based metallic glass

2020 ◽  
Vol 119 ◽  
pp. 106716 ◽  
Author(s):  
X.D. Wang ◽  
P. Liu ◽  
Z.W. Zhu ◽  
H.F. Zhang ◽  
X.C. Ren
Keyword(s):  
Metallic Glass ◽  
Endurance Limit ◽  
High Fatigue ◽  
Fatigue Endurance

Behavior of Plastic Collapse Moments for Pipes With Two Non-Aligned Flaws

2010 ◽  
Author(s):  
Kunio Hasegawa ◽  
Katumasa Miyazaki ◽  
Koichi Saito
Keyword(s):  
Ambient Temperature ◽  
Stainless Steels ◽  
Outer Wall ◽  
Full Scale ◽  
Axial Distance ◽  
Plastic Collapse ◽  
Bending Tests ◽  
Surface Flaws ◽  
Static Failure ◽  
Pipe Materials

Alignment rules for multiple flaws vary between fitness-for-service procedures in different countries. In order to understand the behavior of alignment rules, quasi static failure bending tests have been performed on 2- and 4-inch diameter full-scale pipes with two similar flaws at ambient temperature. The pipe materials employed in the experiments were both ferritic and stainless steels. The two flaws are circumferential surface flaws situated inside the pipes. The non-aligned flaws are located in the circumferential distance S and axial distance H. The experiments showed that when the flaw shapes were short and deep, maximum loads occurred after the flaws had penetrated to the outer wall of the pipes. When the flaws were long and shallow, maximum loads occurred at the point when the flaws penetrated the outer wall of the pipe. With respect to the maximum loads under the condition of the same circumferential distance S, the maximum loads were found to increase with increasing axial distance H for short and deep flaws. However, the maximum loads were found to be unaffected by H for long and shallow flaws.

Properties of ZrO2/Glass-Ceramics Composite

2007 ◽  
Vol 280-283 ◽  
pp. 995-998
Author(s):  
Y.M. Zhu ◽  
Xia Wan Wu ◽  
Zhi Hong Li
Keyword(s):  
Thermal Expansion ◽  
Flexural Strength ◽  
Glass Powder ◽  
Sintering Temperature ◽  
Raw Materials ◽  
Glass Ceramics ◽  
Glass Content ◽  
Thermal Expansion Coefficients ◽  
Lower Thermal Expansion ◽  
Expansion Coefficients

In order to reduce the raw materials cost, lower the sintering temperature of 3Y-TZP optical fiber ferrules, the 3Y-TZP/ LAS glass ceramics composites were prepared and their properties were investigated in this paper. The results showed that the sintering temperatures and thermal expansion coefficients of the 3Y-TZP/LAS glass ceramics composites were lowered with the increase of glass content. The flexural strength of the composites were decreased with the increase of glass content, but the flexural strength of the composite with 15% weight glass was higher than 400MPa. The LAS glass powder added into the composites was crystallized and b-spodumene s.s was precipitated. during sintering. The b-spodumene s.s. having lower thermal expansion coefficient and higher strength was beneficial to reduce thermal expansion coefficients and keep higher strengths of the composites .

Thermodynamic and Kinetic Analysis for Transformation of Oxide Inclusions in Solid 304 Stainless Steels

2019 ◽  
Vol 90 (7) ◽  
pp. 1800600 ◽  
Author(s):  
Jujin Wang ◽  
Weifu Li ◽  
Ying Ren ◽  
Lifeng Zhang
Keyword(s):  
Kinetic Analysis ◽  
Stainless Steels ◽  
Oxide Inclusions

Preparation of Transparent Cellulose/PMMA Composite Sheet from Cellulose Aerogel

2018 ◽  
Vol 773 ◽  
pp. 56-61
Author(s):  
Sawitree Sinthu ◽  
Kawee Srikulkit
Keyword(s):  
Thermal Expansion ◽  
Coefficient Of Thermal Expansion ◽  
Cellulose Solution ◽  
Composite Sheet ◽  
Pmma Sheet ◽  
Cellulose Aerogel ◽  
Index Matching ◽  
Refractive Index Matching ◽  
Lower Thermal Expansion ◽  
Plastic Mold

In this work, wet cellulose aerogel sheet was prepared via NaOH/urea dissolution system followed by multiple solvent exchanges. Firstly, hyacinth cellulose solution was prepared and then cast into plastic mold. The casting solution was left standing to become solid hydrogel. Then, multiple solvent exchanges by water was carried out in order to remove NaOH and urea completely to obtain wet hydrogel. Then, transparent cellulose sheet was successfully prepared by backfilling the nano/micro sized aerogel channel with a refractive index matching polymer which was PMMA emulsion in this study. The transparent cellulose sheet exhibited 80-90 percent transparency. In contrast, cellulose aerogel exhibited relatively low percent transmittance only 8.24%. In addition, the coefficient of thermal expansion (CTE) of transparent cellulose sheet with a thickness of 0.5 mm (10.45 ppmK-1) was significantly lower that pure PMMA sheet (79.70 ppmK-1), indicating that aerogel based transparent cellulose exhibited lower thermal expansion than neat plastic.

Properties of Boehmite AlO(OH) Nanoparticles as the Coatings and Fillers

2012 ◽  
Vol 512-515 ◽  
pp. 604-608 ◽  
Author(s):  
Naofumi Nagai ◽  
Kazuhiro Ihara ◽  
Ayaka Itoi ◽  
Tetsuya Kodaira ◽  
Yukiya Hakuta ◽  
...  
Keyword(s):  
Thermal Expansion ◽  
Gas Permeability ◽  
Porous Alumina ◽  
Composite Films ◽  
Organic Polymer ◽  
Aspect Ratios ◽  
Boehmite Nanoparticles ◽  
Lower Thermal Expansion ◽  
Different Shapes ◽  
Graphite Sheets

Boehmite nanoparticles with different shapes and lengths were used in the preparation of the boehmite films and coatings, and as the fillers for an organic polymer. Then, it was investigated how the shapes and lengths of the particles reflected the characteristics of the films, coatings and fillers. The films were prepared by casting an aqueous sol of the nanoparticles on a Teflon-lined plate, drying and peeling. The coatings were fabricated on porous alumina tubes or graphite sheets by dipping the substrates into a sol of the nanoparticles. The boehmite-polyvinyl alcohol (PVA) composite films, in which the nanoparticles are fillers, were prepared by casting a mixture of a boehmite nanoparticle sol and PVA. The films, coatings and composites were characterized by TEM, TG-DTA, gas permeability, pore size distribution and thermal expansion measurements. In the films, fibrous particles with aspect ratios over 50 aggregated in parallel to each other to form slit-like micropores, on the other hand, plate- and rod-like particles with aspect ratios below 10 randomly aggregated to form meso pores. Corresponding to this, for the coatings on porous alumina tubes and graphite sheets, the fibrous particles gave much low gas permeability and high thermostability, respectively, compared with the plate-like and rod-like particles. For the boehmite-PVA composite films, the fibrous particles gave lower thermal expansion than the plate-like and rod-like particles.

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