scholarly journals Effect of Plasma Nitriding on the Creep and Tensile Properties of the Ti-6Al-4V Alloy

Metals ◽  
2018 ◽  
Vol 8 (8) ◽  
pp. 618 ◽  
Author(s):  
Gisele Almeida ◽  
Antônio Couto ◽  
Danieli Reis ◽  
Marcos Massi ◽  
Argemiro da Silva Sobrinho ◽  
...  
Keyword(s):  
Creep Resistance ◽  
Plasma Nitriding ◽  
Nitrided Layer ◽  
Tensile Tests ◽  
Secondary Creep ◽  
Creep Tests ◽  
Temperature Range ◽  
Gas Atmosphere ◽  
Creep Time ◽  
Increased Strength

This work aimed to enhance the creep resistance of Ti-6Al-4V alloy treated by plasma nitriding. The nitriding was performed on specimens with a Widmanstätten microstructure for four hours at 690 °C under a gas atmosphere containing Ar:N2:H2 (0.455:0.455:0.090). X-ray diffraction analysis showed that the ε-Ti2N and δ-TiN formed on the nitrided sample, in addition to the α-Ti and β-Ti matrix phases. The layer thickness of this sample was about 1 µm. Hot tensile tests were performed in the temperature range of 500 to 700 °C on nitrided and non-nitrided samples, which indicated an increased strength of the nitrided samples. The same temperature range was used for the creep tests in a stress range of 125 to 319 MPa. The plasma-nitrided samples exhibited better creep resistance when compared to the untreated samples. This result was demonstrated by the decreased secondary creep rate and the increased final creep time. This improvement in the creep resistance appeared to be associated with the formation of the nitrided layer, which worked as a barrier to oxygen diffusion into the material and due to the formation of a surface residual compressive stress.

scholarly journals Influence of Zirconia Plasma-Sprayed Coating on Creep of the Ti-6Al-4V Alloy

2006 ◽  
Vol 530-531 ◽  
pp. 690-695 ◽  
Author(s):  
Danieli A.P. Reis ◽  
Cosme Roberto Moreira Silva ◽  
Maria do Carmo de Andrade Nono ◽  
M.J.R. Barboza ◽  
Francisco Piorino Neto ◽  
...  
Keyword(s):  
Creep Resistance ◽  
Surface Oxidation ◽  
Constant Load ◽  
Nitrogen Atmosphere ◽  
High Temperature Strength ◽  
Secondary Creep ◽  
Creep Tests ◽  
Oxidation Protection ◽  
Sprayed Coating ◽  
Plasma Sprayed

The titanium affinity by oxygen is one of main factors that limit the application of their alloys as structural materials at high temperatures. Notables advances have been obeserved in the development of titanium alloys with the objective of improving the specific high temperature strength and creep-resistance properties. However, the surface oxidation limits the use of these alloys in temperatures up to 600°C. The objective of this work was estimate the influence of the plasma-sprayed coatings for oxidation protection on creep of the Ti-6Al-4V alloy, focusing on the determination of the experimental parameters related to the primary and secondary creep states. Constant load creep tests were conducted with Ti-6Al-4V alloy in air for coated and uncoated samples and in nitrogen atmosphere for uncoated samples at 500°C to evaluate the oxidation protection on creep of the Ti-6Al-4V alloy. Yttria (8 wt.%) stabilized zirconia (YSZ) with a CoNiCrAlY bond coat was atmospherically plasma sprayed on Ti-6Al-4V specimens. Results indicated the creep resistance of the coated alloy was greater than uncoated in air, but nitrogen atmosphere was more efficient in oxidation protection. Previously reported results about the activation energies and the stress exponents values indicate that the primary and stationary creep, for both test conditions, was probably controlled by dislocation climb. Occurred a decreasing of steady state creep in function of the reduction of oxidation process, showing that Ti-6Al-4V alloy lifetime was strongly affected by the atmosphere due the oxidation suffered by the material.

scholarly journals Mechanical Behavior of Inconel 625 at Elevated Temperatures

2018 ◽  
Author(s):  
Mauro M. de Oliveira ◽  
Antônio A. Couto ◽  
Gisele F. C. Almeida ◽  
Danieli A. P. Reis ◽  
Nelson B. de Lima ◽  
...  
Keyword(s):  
Elevated Temperatures ◽  
Aging Effect ◽  
Tensile Tests ◽  
Constant Load ◽  
Anomalous Behavior ◽  
Inconel 625 ◽  
Dynamic Strain ◽  
Intergranular Cracking ◽  
Creep Tests ◽  
Temperature Range

Abstract: The Inconel 625 is a nickel-based alloy has been widely used in the high-temperature application. The Inconel 625 exhibits unstable plastic flow at elevated temperature characterized by serrated yielding, known as Portevin-Le Chatelier effect. The aim of this work is to evaluate the mechanical properties at high temperatures of the Inconel 625. The tensile tests were performed in the temperature range of room temperature until 1000 °C and strain rate of 2x10^-4 to 2x10^-3 s^-1. The creep tests were performed in the temperature range of 600-700 °C, in the stress range of 500-600 MPa in a constant load mode. The surface fracture was observed by optical and scanning electron microscopy. Serrated stress-strain behavior was observed in the curves obtained at 200 to 700 °C, which was associated with the dynamic strain aging effect. The yield strength and the elongation values show an anomalous behavior as a function of the test temperature. An intergranular cracking was observed specimen tensile tested at 500 °C that can be attributed to the decohesion of the carbides along the grain boundaries. The fracture surface of the specimen tensile tested at 700 °C showed the predominance of transgranular cracking with tear dimples with a parabolic shape.

scholarly journals CREEP RESISTANCE OF FERRITIC-MARTENSITIC STEEL 16Cr12MoWSiVNbB (EP-823)

2019 ◽  
Vol 62 (4) ◽  
pp. 290-302
Author(s):  
M. Yu. Belomyttsev ◽  
V. G. Molyarov
Keyword(s):  
Ultimate Strength ◽  
Creep Resistance ◽  
Rupture Strength ◽  
Tensile Tests ◽  
Basic Material ◽  
Compression Tests ◽  
Creep Tests ◽  
Delta Ferrite ◽  
Definition Of ◽  
Creep Velocity

Base characteristics of ferritic-martensitic heat resisting steels with 12 % of chrome are parameters of their strength and creep resistance at temperatures of 600 – 750 °С. Steel 16Cr12MoWSiVNbB (EP-823) is considered as the basic material for manufacturing environments fuel rods (TVEL) of a developed reactor with natural safety of BRESTtype. In the literature, there are data about its mechanical characteristics for tensile tests in a range of temperatures of 20 – 750 °С and the limited characteristics of rupture strength. Data on its creep velocity is absent. Laws of creep of steel EP-823 were investigated on metal of three heats with weight of 3 kg. The compression tests at air were applied for cylindrical samples of 5 ÷ 6 mmat temperatures of 600 – 760 °С and stresses of 70 – 310 MPa. The base of compression tests did not exceed 11 hours. The structure after quenching and tempering consisted of tempered martensite and 6 – 12 vol. % of delta-ferrite, the grain size was less 20 μm. It is shown, that the description of creep tests results in double logarithmic (log (σ) – log (έ)) coordinates provides the best concurrence of results of approximation and experiment, than in half-logarithmic (σ – log (έ)). The analysis of parametrical dependences on Hollomon’s PS = (T/1000)[CS – log (έ) and to Larsen-Miller’s PE = (T/1000)[СE – log (σ)] has allowed to find the equations for creep velocity for the set pressure level of 100 – 220 MPa in the form of log (έ) = –19,355 + 9,17 (T/1000) log (σ) and ultimate strength of creep under the set admissions for creep velocity of 0,01 – 1 %/hour in the form of log (σ) = 4,304 – – 0,109 (T/1000) [20 – log (έ)]. Calculations of ultimate strength of creep and creep velocity on pair models and models of Hollomon (Larsen-Miller) give close results, but the preference should be given the second ones as these models consider all three varied factors. Data of control tests under the scheme of a tensile in the same conditions are cited. It is shown, that between results of tests on compression and on tensile at definition of durability characteristics, there is the linear dependence expressed by the equation σ0.2 at compression = 1.3σ0.2 at tensile. At the analysis of creep it has been established, that creep velocity for steel of one grade (09Cr12W3NbB) and for one heat at different type of loading (tensile or compression) have similar values while creep velocities for steel of one grade (EP-823), but of different heats even at one type of loading – compression, can differ substantially.

scholarly journals The microstructure and creep properties of as-cast Mg-Sn-Si-(Al) magnesium alloys

2020 ◽  
Vol 20 (3) ◽  
Author(s):  
Tomasz Rzychoń
Keyword(s):  
Electron Microscopy ◽  
Rare Earth ◽  
Ambient Temperature ◽  
Tensile Properties ◽  
Magnesium Alloys ◽  
Creep Resistance ◽  
Solution Treatment ◽  
Tensile Tests ◽  
Creep Tests ◽  
Creep Properties

Abstract Magnesium alloys containing rare earth metals exhibit good creep resistance up to 300 °C and good tensile properties at ambient temperature. The high cost of rare earth has led to studies regarding the creep resistance of Mg alloys with cheap alloying elements (Sn, Ca, Si) that could be substituted for Mg-RE alloys. In this paper, the influence of Si and Al on microstructure and mechanical properties of Mg-7Sn alloy was investigated using optical (LM), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction analysis (XRD), tensile tests and creep tests at 200–250 °C. Microstructure of as-cast alloys consists of α-Mg matrix and intermetallic compounds at the interdendritic regions. Heat treatment consisting of solid solution treatment and ageing increases the tensile properties at ambient temperature due to the precipitation of the fine Mg2Sn phase. The creep resistance of aged Mg-7Sn alloy is poor. The addition of Si and Al to Mg-7Sn alloy has resulted in improving the creep resistance due to the refinement of Mg2Sn phase and the appearance of Mg2Si phase at the grain boundaries. The Mg-7Sn-1Si alloy exhibits better creep resistance at 200 °C than Mg-7Sn-5Si and Mg-7Sn-5Si-2Al alloys. The Mg-7Sn alloys with 5% Si have better creep properties at 250 °C in comparison to Mg-7Sn-1Si alloy.

scholarly journals Creep Damage Repair of a Nickel-Based Single Crystal Superalloy Based on Heat Treatment

Metals ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 623
Author(s):  
Xiaoyan Wang ◽  
Meng Li ◽  
Yuansheng Wang ◽  
Chengjiang Zhang ◽  
Zhixun Wen
Keyword(s):  
Heat Treatment ◽  
Single Crystal ◽  
Creep Damage ◽  
Primary Creep ◽  
Single Crystal Superalloy ◽  
Secondary Creep ◽  
Creep Life ◽  
Phase Coarsening ◽  
Damage Repair ◽  
Creep Time

Taking nickel-based single crystal superalloy DD6 as the research object, different degrees of creep damage were prefabricated by creep interruption tests, and then the creep damage was repaired by the restoration heat treatment system of solid solution heat treatment and two-stage aging heat treatment. The results show that with the creep time increasing, the alloy underwent microstructure evolution including γ′ phase coarsening, N-type rafting and de-rafting. After the restoration heat treatment, the coarse rafted γ′ phase of creep damaged specimens dissolved, precipitated, grew up, and became cubic again. Except for the specimens with creep interruption of 100 h, the γ′ phase can basically achieve the same arrangement as the γ′ phase of the original sample. The comparison of the secondary creep test shows that the steady-state creep stage of the test piece after the restoration heat treatment is relatively increased, and the total creep life can reach the same level as the primary creep life. The high temperature creep properties of the tested alloy are basically recovered, and the restoration heat treatment effect is good.

Creep Properties and Interfacial Microstructure of SiC Whisker Reinforced Si3N4

1989 ◽  
Vol 170 ◽  
Author(s):  
Håkan A. Swan ◽  
Colette O'meara
Keyword(s):  
High Temperature ◽  
Creep Resistance ◽  
Interfacial Microstructure ◽  
Deformation Mechanisms ◽  
Amorphous Films ◽  
Creep Tests ◽  
Creep Properties ◽  
High Temperature Exposure ◽  
Temperature Exposure

AbstractPreliminary creep tests were performed on SiC whisker reinforced and matrix Si3N4 material fabricated by the NPS technique. The material was extensively crystallised in the as received material, leaving only thin amorphous films surrounding the grains. No improvement in the creep resistance could be detected for the whisker reinforced material. The deformation mechanisms were found to be that of cavitation in the form of microcracks, predominantly at the whisker/matrix interfaces, and the formation of larger cracks. Extensive oxidation of the samples, as a result of high temperature exposure to air, was observed for the materials tested at 1375°C.

Effect of Equal-Channel Angular Pressing (ECAP) on Creep in Aluminium Alloys

2007 ◽  
Vol 539-543 ◽  
pp. 2904-2909 ◽  
Author(s):  
Vàclav Sklenička ◽  
Jiří Dvořák ◽  
Marie Kvapilová ◽  
Milan Svoboda ◽  
Petr Král ◽  
...  
Keyword(s):  
Equal Channel Angular Pressing ◽  
Aluminium Alloys ◽  
Creep Resistance ◽  
Room Temperature ◽  
Creep Behaviour ◽  
Coarse Grained ◽  
Pure Aluminium ◽  
Creep Tests ◽  
Angular Pressing ◽  
Compression Creep

This paper examines the effect of equal-channel angular pressing (ECAP) on creep behaviour of pure aluminium, binary Al-0.2wt.%Sc alloy and ternary Al-3wt.%Mg-0.2wt.%Sc alloy. The ECAP was conducted at room temperature with a die that had a 90° angle between the channels and 8 repetitive ECAP passes followed route BC. Constant stress compression creep tests were performed at 473 K and stresses ranging between 16 to 80 MPa on ECAP materials and, for comparison purposes, on the initial coarse-grained materials. The results showed that the creep resistance of the ECAP processed Al-Sc and Al-Mg-Sc alloys was markedly deteriorated with respect to unpressed coarse-grained materials.

Nitriding of yttria-stabilized zirconia in atmospheric pressure microwave plasma

2009 ◽  
Vol 24 (6) ◽  
pp. 2021-2028 ◽  
Author(s):  
R. Milani ◽  
R.P. Cardoso ◽  
T. Belmonte ◽  
C.A. Figueroa ◽  
C.A. Perottoni ◽  
...  
Keyword(s):  
Photoelectron Spectroscopy ◽  
Atmospheric Pressure ◽  
Microwave Plasma ◽  
Plasma Nitriding ◽  
Nitrided Layer ◽  
Zirconium Nitride ◽  
Stabilized Zirconia ◽  
Partially Stabilized Zirconia ◽  
X Ray ◽  
Yttria Partially Stabilized Zirconia

High temperature plasma nitriding of yttria-partially-stabilized zirconia in atmospheric pressure microwave plasma was investigated. The morphological, mechanical, and physicochemical characteristics of the resulting nitrided layer were characterized by different methods, such as optical and scanning electron microscopy, microindentation, x-ray diffraction, narrow resonant nuclear reaction profiling, secondary neutral mass spectrometry, and x-ray photoelectron spectroscopy, aiming at investigating the applicability of this highly efficient process for nitriding of ceramics. The structure of the plasma nitrided layer was found to be complex, composed of tetragonal and cubic zirconia, as well as zirconium nitride and oxynitride. The growth rate of the nitrided layer, 4 µm/min, is much higher than that obtained by any other previous nitriding process, whereas a typical 50% increase in Vickers hardness over that of yttria-partially-stabilized zirconia was observed.

Formability and Process Conditions of Magnesium Alloy Sheets

2005 ◽  
Vol 488-489 ◽  
pp. 453-456 ◽  
Author(s):  
Shi Hong Zhang ◽  
Yong Chao Xu ◽  
G. Palumbo ◽  
S. Pinto ◽  
Luigi Tricarico ◽  
...  
Keyword(s):  
Deep Drawing ◽  
Tensile Tests ◽  
Process Conditions ◽  
Drawing Ratio ◽  
Temperature Range ◽  
Fine Grained ◽  
Axial Tensile ◽  
Die Surface ◽  
Lower Temperature Range ◽  
Lower Temperature

Comparing the formability with each other, extrusion and various rolling experiments were carried out to make fine-grained AZ31 Mg sheets, and uni-axial tensile tests were carried out at different strain rates and temperatures to investigate the effect of different variables. A warm deep drawing tool setup with heating elements, which were distributed under the die surface and inside the blank holder, was designed and manufactured, and deep drawing was performed. Extruded Mg alloy AZ31 sheets exhibit the best deep drawing ability when working in the temperature range 250-350°C. Extruded and rolled sheets of 0.8 mm thick were also deep drawn in the lower temperature range 105-170°C，showing good formability and reaching a Limit Drawing Ratio up to 2.6 at 170°C for rolled sheets. At last, a sheet cup 0.4 mm thick was deep drawn successfully at 170 °C.

Heat Treatments Effect on the Mechanical Properties of Industrial Drawn Copper Wires

2013 ◽  
Vol 811 ◽  
pp. 9-13 ◽  
Author(s):  
Zakaria Boumerzoug ◽  
Zakaria Boumerzoug ◽  
Vincent Ji
Keyword(s):  
Mechanical Properties ◽  
Cross Section ◽  
Treatment Time ◽  
Void Formation ◽  
Tensile Tests ◽  
Heat Treatments ◽  
Ambient Atmosphere ◽  
Creep Tests ◽  
Prior Heat Treatment ◽  
Industrial Material

In this present investigation, the mechanical properties of industrial drawn copper wires have been studied by creep tests, tensile tests and hardness Vickers. The effect of prior heat treatments at 500°C for different time on the drawn wires behavior was the main goal of this investigation. We have found that these heat treatments influenced the creep behavior of drawn wires and recorded shape curves. The creep tests were applied under ambient atmosphere at 240 °C. The creep duration before rupture decreased with the prior heat treatment time. The creep tests results were confirmed by tensile tests. A relationship between the hardness and the ultimate tensile strength of this industrial material has been established. Optical and scanning electron microscopy observations have been also used. Cross section observations of the wire after tensile or creep-rupture tests have shown that the mechanism of rupture was mainly controlled by the void formation.

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