Comparation between PIII Superficial and Ceramic Coating in Creep Test of Ti-6Al-4V Alloy

The objective of this work was evaluating the creep resistance of the Ti-6Al-4V alloy with superficial treatment of PIII superficial treatment and ceramic coating in creep test of Ti-6Al-4V alloy. It was used Ti-6Al-4V alloy as cylindrical bars under forged and annealing of 190oC by 6 hours condition and cooled by air. The Ti-6Al-4V alloy after the superficial treat-ment of PIII and ceramic coating was submitted to creep tests at 600°C and 250 and 319 MPa under constant load mode. In the PIII treatment the samples was put in a vacuum reactor (76x10-3 Pa) and implanted by nitrogen ions in time intervals between 15 and 120 minutes. Yttria (8 wt.%) stabilized zirconia (YSZ) with a CoNiCrAlY bond coat was atmospherically plasma sprayed on Ti-6Al-4V substrates by Sulzer Metco Type 9 MB. The obtained results suggest the ceramic coating on Ti-6Al-4V alloy improved its creep resistance

Dendritic spacing and macrosegregation affecting microhardness of an al-si-mg alloy solidified under unsteady state conditions

The prediction of microstructure morphology is fundamental for the manufacture of metallic components, since the expected levels of mechanical properties will be associated with the final aspects of the microstructure. In this work, an Al-7wt.%Si-3wt.%Mg alloy was directionally solidified in unsteady state conditions in order to investigate the influence of the addition of 3wt.%Mg to an Al-7wt.%Si alloy on the solidification evolution. The microstructure of the examined alloy is shown to be characterized by a more complex arrangement of phases, as compared to that of the Al-7wt.%Si alloy, which includes the binary (α-Al+Mg2Si) and refined ternary (α-Al+Si+Mg2Si+Fe-rich IMC) eutectic mixtures. A higher Vickers hardness profile is shown to be associated with a more refined microstructural arrangement. However, for cooling rates lower than 2K/s the microhardness is shown to increase with the increase in the microstructural spacing, which is shown to occur caused by Si macrosegregation and higher content of free Mg221CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQCOORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL DE NÍVEL SUPERIOR - CAPESFUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESP407871/2018-70012012/08494-0; 2013/23396-7; 2014/25809-0The authors thank the financial support provided by Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - Brasil (CAPES) - Finance Code 001, FAPESP- São Paulo Research Foundation (Grants 2012/08494-0; 2013/23396-7 and 2014/25809-0) and CNPq - National Council for Scientific and Technological Development (grant 407871/2018-7). CNPEM and LNNano for the use of the XRD equipment. The authors thank Lilian Uematsu for the language support

Assessing Microstructure Tensile Properties Relationships in Al-7Si-Mg Alloys via Multiple Regression

The development of Al-based alloys presumes a detailed understanding of the microstructure evolution during solidification since the as-solidified microstructure also has effects on the subsequent thermo-mechanical processing. In the present investigation Al-7wt.%Si-xMg (x = 0.5 and 1 wt.%) alloys are subjected to transient directional solidification with a view to characterizing the microstructure evolution, with special focus on both dendritic evolution and the inherent features of the Mg2Si and π-AlSiFeMg intermetallics. Experimental power-type functions relating the primary, secondary and tertiary interdendritic spacings to the solidification cooling rate and growth rate are developed. It is observed that the Mg content added to the Al-7wt.%Si alloy and the consequent increase in the Mg2Si fraction tends to increase the values of the primary dendritic spacing. However, this same behavior is not verified for the growth evolution of dendritic side branches. A multiple linear regression (MLR) analysis is developed permitting quantitative correlations for the prediction of tensile properties and hardness from microstructural parameters to be established. The increase in the Mg alloy content from 0.5 to 1 was shown to promote an increase in both the ultimate tensile strength (σu) and elongation

Assessing Microstructure Tensile Properties Relationships in Al-7Si-Mg Alloys via Multiple Regression

The development of Al-based alloys presumes a detailed understanding of the microstructure evolution during solidification since the as-solidified microstructure also has effects on the subsequent thermo-mechanical processing. In the present investigation Al-7wt.%Si-xMg (x = 0.5 and 1 wt.%) alloys are subjected to transient directional solidification with a view to characterizing the microstructure evolution, with special focus on both dendritic evolution and the inherent features of the Mg2Si and π-AlSiFeMg intermetallics. Experimental power-type functions relating the primary, secondary and tertiary interdendritic spacings to the solidification cooling rate and growth rate are developed. It is observed that the Mg content added to the Al-7wt.%Si alloy and the consequent increase in the Mg2Si fraction tends to increase the values of the primary dendritic spacing. However, this same behavior is not verified for the growth evolution of dendritic side branches. A multiple linear regression (MLR) analysis is developed permitting quantitative correlations for the prediction of tensile properties and hardness from microstructural parameters to be established. The increase in the Mg alloy content from 0.5 to 1 was shown to promote an increase in both the ultimate tensile strength (σu) and elongation

Plasma torch for supersonic plasma spray at atmospheric pressure

This work presents a plasma torch able to operate at supersonic regime with axial injection of feedstock. In contrast to commonly used linear scheme, the principal axis of the plasma torch is perpendicular to feedstock injection direction, which is aligned with coming out plasma jet. The plasma torch has slightly ascending current voltage characteristics and fixed arc length. Electrical, thermal and kinetic characteristics outlined from comparison with conventional linear plasma spray torches are intermediate between APS, HVOF and VPS. The plasma torch developed in this work has an elevated arc voltage (370V) and low arc current (100A), which contribute to increase the electrode life and decrease the arc voltage relative fluctuation (10%). According to in-flight particle monitoring the CoNiCrAlY particles were sprayed at 500 m/s and temperature of 2400 degrees C, whereas the 7%YSZ at 491-683 m/s and 2535-2636 degrees C. (C) 2016 Elsevier B.V. All rights reserved.Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Univ Fed Sao Paulo, UNIFESP, Inst Ciencia & Tecnol, BR-12231280 Sao Jose Dos Campos, SP, BrazilITA, Lab Plasmas & Proc, BR-12228900 Sao Jose Dos Campos, SP, BrazilHMTI Natl Acad Sci Belarus, Luikov Heat & Mass Transfer Inst, Minsk 220072, ByelarusUniv Estadual Paulista, UNESP, Inst Ciencia & Tecnol, BR-12247004 Sao Jose Dos Campos, SP, BrazilInstituto de Ciência e Tecnologia, Universidade Federal de São Paulo – UNIFESP, São José dos Campos 12231-280, SP, BrazilFAPESP: 2012/24851-7CNPq: 2012/24851-7CAPES: 2012/24851-7Web of Scienc

Mechanical Behavior of Inconel 625 at Elevated Temperatures

Inconel 625 is a nickel-based alloy that is mainly used in high-temperature applications. Inconel 625 exhibits an unstable plastic flow at elevated temperatures characterized by serrated yielding, well-known as the Portevin-Le Chatelier effect. The evaluation of the mechanical properties of Inconel 625 at high temperatures is the aim of this work. The tensile tests were executed in temperatures ranging from room temperature to 1000 °C with strain rates of 2 × 10−4 to 2 × 10−3 s−1. The creep tests were executed in the temperature range of 600–700 °C and in the stress range of 500–600 MPa in a constant load mode. The optical and scanning electron microscopes were used for surface fracture observation. In the curves obtained at 200–700 °C the serrated stress-strain behavior was observed, which was related to the dynamic strain aging effect. The yield strength and the elongation values show anomalous behavior as a function of the test temperature. An intergranular cracking was observed for a 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

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

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