Surface chemical state of Ti powders and its alloys: Effect of storage conditions and alloy composition

Hryha, Eduard; Shvab, Ruslan; Bram, Martin; Bitzer, Martin; Nyborg, Lars

doi:10.1016/j.apsusc.2016.01.046

Cited by 49 publications

(30 citation statements)

References 24 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Therefore, part of the total oxygen content in a Ti powder is logically in the form of oxides on the surface of each particle. There have been reports of studies on the thickness of the oxide layer on Ti metal particles by using the X-ray photoelectron spectroscopy (XPS) technique, and the oxide layer can change its thickness and composition depending on the aging time and temperature [30], ranging from 3-8 nm at room temperature [31]. It has been estimated that for Ti a spherical particle of 2 μm in diameter and 3 nm in surface layer thickness, the surface oxygen content can be around 3900 ppm [32].…”

Section: Surface Oxygen Vs Lattice Oxygenmentioning

confidence: 99%

Hydrogen assisted magnesiothermic reduction of TiO2

Zhang

Fang

Yang

et al. 2017

Chemical Engineering Journal

View full text Add to dashboard Cite

The development of low cost titanium metal production processes has challenged the Ti research and industrial communities around the world for decades. The strong affinity of titanium to oxygen dictates that it is very difficult to produce low-oxygen Ti metal from TiO 2 directly. In this paper, a hydrogen assisted magnesiothermic reduction (HAMR) process for producing Ti metal powder from TiO 2 powder at relatively low temperatures (750°C) is established. The overall approach is based on the thermodynamic tuning of the relative stability of MgO versus that of Ti-O solid solutions by temporarily alloying the system with hydrogen. It is shown that Ti-H-O solid solutions are less stable than their corresponding Ti-O solid solutions, which changes the reaction of Mg with Ti-O from being thermodynamically unfavorable to being favorable. The key steps for producing pure Ti metal powder from TiO 2 involve Mg reduction of TiO 2 in a hydrogen atmosphere which produces porous TiH 2 , a heat treatment procedure to consolidate the powder and reduce specific surface area of the powder, and the final step to deoxygenate the powder using Mg in a hydrogen atmosphere to further reduce the oxygen content. This paper systematically examines the changes of oxygen content, phase transformations, and the evolution of the

show abstract

Section: Surface Oxygen Vs Lattice Oxygenmentioning

confidence: 99%

Hydrogen assisted magnesiothermic reduction of TiO2

Zhang

Fang

Yang

et al. 2017

Chemical Engineering Journal

View full text Add to dashboard Cite

show abstract

“…The etch rate was calibrated on a flat oxidized tantalum foil with the well-known Ta2O5 thickness (100 nm). Hence, the oxide thickness refers to Ta 2 O 5 units [6].…”

Section: Methodsmentioning

confidence: 99%

“…Therefore, experimental error of the binding energy shift was smaller than this value. The recorded photoelectron peaks were curve fitted utilizing the PHI Multipak software (Perkin Elmer, Waltham, Massachusetts, USA) with asymmetric curves and assuming Shirley background [6].…”

Section: Methodsmentioning

confidence: 99%

“…These techniques enable evaluation of the distribution of the secondary phases on the nano-level (thickness of the surface oxide films, presence, size and distribution of the secondary phases, etc. ), as well as powder surface morphology [5][6][7][8][9].…”

Section: Introductionmentioning

confidence: 99%

“…Chemical composition, morphology and distribution of the oxide phases on the powder surface determine the conditions required for oxide removal/redistribution in order to form strong inter-particle necks. Strong and defectfree inter-particle connections are required to reach high mechanical performance of the final component [5,6].…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Copper Bronze Powder Surface Studied by XPS and HR SEM

Shvab

Hryha

Tahir³

et al. 2016

Powder Metallurgy Progress

View full text Add to dashboard Cite

The state of the powder surface represents one of the main interests in the whole cycle of components' production using powder metallurgy (PM) INTRODUCTIONComponents produced by casting, forming, shaping and even made by near-net or netshape methods, often require further operations before the product is ready for use. Machining, which involves secondary and finishing operations, is usually applied at the end of the manufacturing process to meet all the demands required for the component [1]. Grinding is one of the most important finishing operations because of its capability to impart high dimensional accuracy and surface finish. Grinding is a metal cutting process using tools with multiple cutting edges provided by randomly bonded abrasive grits of natural and/or synthetic origin which remove material at high speed. Metal-bonded grinding wheels use the metal bond to hold the abrasive grit (cubic boron nitride, diamond, etc.) for high performance applications. Using different powder metallurgy (PM) techniques, abrasive grits are mixed with metal bond powder and some additives and subsequent bonding is carried out under high pressure and temperature. The high thermal conductivity, strength and wear resistance of Cu bronze makes it an interesting candidate for the metal bond [1][2][3][4]. Taking into account a high specific surface area of the powder in comparison with the bulk material, surface chemical state is one of the most important aspects determining usability of powder for PM processing. Exposure of the powder to the oxygen

show abstract

Influence of Storage Conditions on Powder Surface State and Hot Deformation Behavior of a Powder Metallurgy Nickel‐Based Superalloy

et al. 2022

View full text Add to dashboard Cite

Powder metallurgy (PM) FGH96 superalloy powders are stored under vacuum, argon, ambient air, and oxygen atmospheres for as long as 500 days. The surface analysis results demonstrate that the chemical state of Ni, Ti, Cr, Co, O, and C remain unchanged after 90 days storage. However, the oxygen content and NiO/Ni(OH)2 layer thickness increase from initial values (∼120 ppm and ∼3.8 nm) to stabilized values (∼200 ppm and ∼10 nm) after a short time storage (7–15 days), and remain basically unchanged with the extension of storage time. Powders stored in oxygen atmosphere possess the highest oxygen content (maximum 213 ppm) while the lowest in vacuum, the gap can reach to 25 ppm. The hot isostatic‐pressed (HIPed) parts that consolidated from original and stored powders are isothermally compressed at different conditions. The results indicate that HIPed parts with more oxygen will cause higher activation energy and narrower processing window due to a lower degree of dynamic recrystallization (DRX). Discontinuous DRX (DDRX) dominates the DRX nucleation mechanism of HIPed FGH96 superalloys with ∼120–200 ppm oxygen content, while continuous DRX (CDRX) is the auxiliary mechanism. The increased oxygen content and surface NiO/Ni(OH)2 layer thickness of superalloy powders generate higher oxygen content of corresponding HIPed parts, thus decreasing the hot workability.

show abstract

Surface chemical state of Ti powders and its alloys: Effect of storage conditions and alloy composition

Cited by 49 publications

References 24 publications

Hydrogen assisted magnesiothermic reduction of TiO2

Hydrogen assisted magnesiothermic reduction of TiO2

Copper Bronze Powder Surface Studied by XPS and HR SEM

Influence of Storage Conditions on Powder Surface State and Hot Deformation Behavior of a Powder Metallurgy Nickel‐Based Superalloy

Contact Info

Product

Resources

About