An investigation on milling rotation speed and addition time of surfactant in synthesis of Ti-Nb-Mo alloy

Advances in Powder Metallurgy &

Particulate Materials—2015

Proceedings of the 2015 International Conference on

Powder Metallurgy & Particulate Materialssponsored by the

Metal Powder Industries FederationMay 17–20, 2015

Compiled by

Sherri R. BingertLos Alamos National Laboratory

Sydney H. LukNorth American Höganäs

Metal Powder Industries Federation105 College Road East

Princeton, New Jersey 08540-6692

Tel: (609) 452-7700 Fax: (609) 987-8523mpif.org

The papers contained in this publication were prepared by the author(s) andreviewed by the session chairmen and submitted for subsequent publication by

direct reproduction. The publisher is not responsible for content and/or anydeviations from oral presentations from which the papers may have been based.

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No part of this publication may be reproduced, stored in a retrieval system, ortransmitted, in any form or by any means, electronic, mechanical, photocopying,

recording or otherwise, without the prior written permission of the publisher._______________________________________________________________

ISBN No. 978-1-943694-01-3

© 2015 Metal Powder Industries Federation105 College Road East

Princeton, New Jersey 08540-6692 USA

All rights reservedProduced in the U.S.A.

FOREWORD

The 2015 International Conference on Powder Metallurgy & Particulate Materials sponsored by the Metal Powder Industries Federation was held May 17th–20th in San Diego, California. This meeting of PM professionals included over 140 presentations in 44 technical sessions, 3 special interest programs, and an international display of posters. Held in parallel with the Additive Manufacturing with Powder Metallurgy Conference, the two conferences attracted 850attendees from more than 30 countries.

Advances in Powder Metallurgy & Particulate Materials—2015 is the compilation of the proceedings of the conference. In addition to the technical papers presented, the proceedings also contain the “State of the North American PM Industry—2015” by Richard Pfingstler, MPIF President, Atlas Pressed Metals.

Special interest programs in 2015 included:

Light MetalsWelding & JoiningDimensional Variation Reduction

In addition to a strong technical program and an opportunity for the exchange of technical knowledge, the exhibit displayed entries for the 2015 PM Design Excellence Awards throughout the event. Eighty-five domestic and international exhibitors representing the latest PM equipment, powders, products, and services were on display.

Our sincere gratitude goes out to all involved for their commitment, time, and talent that madePOWDERMET2015 a success. The Technical Program Committee members demonstratedprofessionalism and true dedication that produced and delivered an exceptional technical program. We also recognize the technical paper and poster authors for their outstanding contributions to the advancement of PM knowledge through technology transfer. The technical advances that are presented at the conference and documented in these proceedings demonstrate the high caliber research and development that all have come to expect from the PM industry and academia. This is what truly sets the POWDERMET community and this conference apart from others. We are grateful to those organizations that supported our committee members and authors; without their support, these professionals would not have hadthe opportunity to educate and advance the industry.

Finally, we extend our heartfelt appreciation to the entire staff of MPIF, whose professionalism made our jobs seem effortless throughout this important and extensive program. Their expertise, dedication, support, and encouragement helped mold all the diverse elements into a world-class conference and assured the continued advancement of the PM industry into the future.

Sherri R. Bingert Sydney LukProgram Chairman Program Chairman

Randall German, FAPMIGerman Materials TechnologyAnne Good PM Engineered SolutionsRyuichiro GotoEngineered Sintered ComponentsOlle Grinder, FAPMIPM Technology ABTimothy HaleHoeganaes CorporationJeffrey HamiltonCloyes Gear & Products, Inc.Francis HanejkoHoeganaes CorporationRobert HayesPhoenix Sintered Metals LLCMichael Hobbs, PMTNorth American Höganäs, Inc.Bo HuNorth American Höganäs, Inc.Edmond Ilia, PMTMetaldyne LLCW. Brian James, FAPMIPMtechThomas JesbergerABBOTT Furnace CompanyThomas JewettGlobal Tungsten & Powders CorporationStefan JoensElnik Systems, LLCJohn JohnsonKennametal Firth SterlingArthur JonesSymmco, Inc.Jessu JoysUnited States Metal Powders Inc.Scott JustusBASF CorporationShiz KassamKeystone Powdered Metal CompanyMartin KearnsSandvik Osprey Ltd.Lou KoehlerKoehler AssociatesJeremy Koth, PMTFederal-Mogul Sintered ProductsJack KrajcirikOsterwalder Inc.Howard KuhnExOne CompanyJane LaGoyBodycote HIPChaman LallMetal Powder Products CompanyRoger Lawcock, FAPMIStackpole InternationalAlan Lawley, FAPMIDrexel UniversityGilles L'Espérance, FAPMIÉcole Polytechnique de MontréalBruce LindsleyHoeganaes CorporationDeepak MadanMagnesium Elektron PowdersMarko MaetzigARBURG GmbH + Co KG

Susan AbkowitzDynamet Technology, Inc.Christopher Adam, PMTRoyal Metal Powders Inc.Iver Eric Anderson, FAPMIAmes LaboratoryRonald Arble, PMTNetShape Technologies, Inc.Satyajit BanerjeeDSH Technologies, LLCRobert BeimelJIT Tool & Die, Inc.Paul Beiss, FAPMIRWTH AachenPaul BishopDalhousie UniversityCarl BlaisLaval UniversityAnimesh Bose, FAPMIMaterials Processing, Inc.Matthew BulgerNetShape Technologies - MIMJulie Campbell-TremblayRio Tinto Metal PowdersArun ChattopadhyayEtimine USA, Inc.Bhanu ChelluriIAP Research, Inc.Russell ChernenkoffMetaldyne LLCDenis Christopherson, PMTFederal-Mogul Sintered ProductsSteve ConstantinidesArnold Engineering CompanyBrandon CreasonKittyhawk ProductsJeffrey DanaherARCMIMScott DavisHoeganaes CorporationDavid DombrowskiLos Alamos National LaboratoryIan Donaldson, FAPMIGKN Sinter MetalsRobert DowdingU.S. Army Research LaboratoryJohn Engquist, FAPMIJENS Solutions LLCRavi EnnetiGlobal Tungsten & Powders CorporationGregory FalleurCloyes Gear & Products, Inc.Zhigang Fang, FAPMIUniversity of UtahKeith FlemingNorth American Höganäs, Inc.Leonid FraymanAllegheny CoatingsCynthia FreebyAmetek, Inc.William Gasbarre, FAPMIGasbarre Products, Inc.Robert GasiorAmetek, Inc.Claude GélinasRio Tinto Metal Powders

Bernhard MaisECKA GranulesNicholas MaresAsbury Graphite Mills, Inc.Michael MarucciHoeganaes CorporationStephen MashlMichigan Technological UniversityJeff MatusikToyota Motor Manufacturing &

EngineeringTimothy McCabeKinetics Climax, Inc.Kylan McQuaigHoeganaes CorporationJose Medina, Jr., PMTABBOTT Furnace CompanyPankaj MehrotraKennametal Inc.Alan MilesFloMet LLCAnthony Miller, PMTIIMicro Metals, Inc.Hideshi MiuraKyushu UniversityCesar Molins, Jr.AMES S.A.Thomas Murphy, FAPMIHoeganaes CorporationK.S. Narasimhan, FAPMIHoeganaes CorporationJoseph NewkirkMissouri Univ. of Science & TechnologySalvator NigaruraPMG Indiana CorporationLuke Nissel, PMTMetco Industries, Inc.Richard ObaraEmerson Climate Technologies, Inc.Valmikanathan OnbattuvelliIntelSunil PatelHoeganaes CorporationThomas PelletiersSCM Metal Products, Inc.Thomas PfingstlerAtlas Pressed MetalsThomas PhilipsAir Products and Chemicals, Inc.Brian PittengerJenike & Johanson, Inc.Thomas PontzerGasbarre Products, Inc.Daniel ReardonABBOTT Furnace CompanyEric ReinertBronson & Bratton, Inc.Heron RodriguesEngineered Sintered ComponentsRajendra SadangiSteven SchmidUniversity of Notre DameJames SearsGE Global Research CenterRaymond Serafini, PMTLinde, LLC

PROGRAM COMMITTEE

Suresh ShahCloyes Gear & Products, Inc.John Shields, Jr.PentaMet Associates LLCRohith ShivanathStackpole InternationalBrian SiegerHonda R&D AmericasBenjamin SlatteryChrysler Corp.Peter SokolowskiHoeganaes CorporationChad SporeJohn DeereBlaine StebickGKN Sinter MetalsJoseph Tunick StraussHJE Company, Inc.Craig StringerAtlas Pressed MetalsMichael StuckyNorwood Injection Technologies, LLCS.K. TamOrmco CorporationRajiv TandonMagnesium Elektron PowdersJason TingRetech Systems LLCTorbjorn TingskogAP&C Advanced Powder & CoatingsJohn von ArxNetShape Technologies, Inc.Shekhar WakadeGeneral Motors CorporationVirendra WarkeEntegris, Inc.Roland Warzel IIINorth American Höganäs, Inc.Glen WeberFord Motor CompanyDwight WebsterAdvanced Metalworking Practices, LLCDonald Whychell, Sr., FAPMICM Furnaces, Inc.Lynn YoungbergCapstan CaliforniaAntonios ZavaliangosDrexel University

Sherri R. Bingert Los Alamos National Laboratory

Sydney H. LukNorth American Höganäs, Inc.PROGRAM CHAIRMEN

TECHNICAL PROGRAM COMMITTEE

An investigation on milling rotation speed and addition time of surfactant in synthesis of Ti-Nb-Mo alloy

Keivan A. Nazaria*, Alireza Nourib, Tim Hilditcha

a School of Engineering, Deakin University, Locked Bag 20000, Geelong VIC 3220 Australia b Institute of Biomaterials and Biomedical Engineering, University of Toronto, Toronto, Ontario, M5S 3G9

Canada

[email protected]

Abstract

The influence of milling rotation speed and the addition time of a surfactant (ethylene bis-stearamide; EBS) on density, hardness and surface properties of sintered Ti-10Nb-3Mo alloy (wt.%) was investigated. Six batches of powders were prepared using high-energy ball milling for 10 h. The total amount of 2 wt.% EBS was added to the powder mixture either prior to milling process or at four time intervals and each batch was run at two rotation speeds of 200 and 300 rpm. Results indicated that ball milling at 300 rpm facilitated the dissolution of solute elements throughout the Ti matrix. Furthermore, finer particles and more uniform powder distribution were obtained when EBS was added to powder mixture at four time intervals during milling process. The sintered compacts made from the ball-milled powders mixed with EBS at four time intervals exhibited higher density and hardness as well as the lowest value of surface roughness (Ra).

1. Introduction

Mechanical alloying (MA) is a powder processing technique carried out with blended elemental powders in a high-energy ball mill to prepare alloyed mixture. The powders obtained by MA can be consolidated in the shape of green compacts and sintered at an appropriate temperature to form final products. There are several processes involved in alloying include repeated welding, fracturing, and rewelding of powders [1-3]. Particles diffuse together via interdiffusion and fracture under high energy collision of the milling balls in a container. However, excessive cold welding leads to an increase in particle size that impede formation of atomically clean surfaces for further interdiffusion. Therefore, balancing the rate of welding and fracturing is essential to prepare a desired fine microstructure and intimate alloying. The addition of organic materials, referred interchangeably as a surfactant or process control agent (PCA), is needed to minimize the excessive cold welding and obtain a balance between fracturing and cold welding of powder particles [2-5].

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Extensive studies and research have been conducted to understand the effect of type and amount of surfactant on the final characteristics and properties of mechanically alloyed powders [6-9]. In other attempt, the effect of regular addition of surfactants on mechanically alloyed powder particles to alter the characteristics and properties of the ball-milled particles has been investigated [10].

In the present work, the authors study the effects of varying rotation speeds and surfactant addition times on morphological and microstructural evolution of Ti-10Nb-3Mo alloy prepared by high-energy ball milling. A further focus is placed on the hardness, density and surface roughness characteristics of the sintered compacts. For this purpose, the total amount of 2 wt.% EBS was added at one and four intervals to Ti-10Nb-3Mo powder mixture and ball milling was performed at two rotation speeds of 200 and 300 rpm for 10 h. The obtained powders and sintered compacts were characterized using scanning electron microscopy (SEM), X-ray diffraction, and profilometer.

2. Materials and methods

As-received powders of Ti (purity 99.7%, , 99.99%, were mixed according to the composition of Ti–10Nb–3Mo (wt.%) alloy. A planetary ball mill (Vacon, Chinese ball milling system) was used and the ball milling was perfromed at rotation speeds of 200 and 300 rpm for 10 h. The grinding media were 10 mm steel balls. The ball-to-powder weight ratio was maintained at 20:1. The powders were loaded in a hardened steel containers in an argon-filled glove box. Six batches of Ti–10Nb–3Mo were prepared. In two batches, the Ti-10Nb-3Mo alloy ball milled for 10 h without the addition of surfactant. In four other batches, EBS [CONHCH2CH3(CH2)16]2 was added into the milling container as a surfactant in the amounts of 2 wt.% before and during the milling. Intermittent milling was performed with intervals of 2.5 h. In order to add EBS to the container and also to avoid the excessive heating during the ball milling, the milling process was stopped every 2.5 h for 30 min. The powders were unloaded from the container inside the glove box chamber under argon gas. Disk-shaped specimens of 10 mm diameter and 3 mm thickness were produced via consolidating the powder using a uniaxial cold press under the pressure of 750 MPa. Sintering of samples was conducted in a high vacuum furnace (10-6 -1. The set up of the experiments is summarized in Table 1.

Table 1. Synthesis of Ti-10Nb-3Mo alloy through ball milling process at two speed rotations of 200 and 300 rpm. Six batches of ball-milled powders were prepared with the addition of EBS as a surfactant at regular time intervals.

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Ball milling time

(h)

Amount of EBS

(wt.%)0 2 0.5

2.5 0.55 0.5

7.5 0.510* Batch #1, Batch #2,5 Batch #3,6

* After 10 h of ball milling, the powders were collected and labeled as batch #1-6.

The morphology and microstructure of the powder particles were characterized by means of a scanning electron microscope (SEM) (Zeiss Supra 55VP) combined with secondary

Samples from each batch were characterized by X-ray diffraction (XRD) using Cu K rate of 0.02 -1 over a 2 angular range of 30–90. The Vickers microhardness of the sintered alloys was measured at a load of 100 g for 15 s. Average hardness values were obtained from at least six indents on each sintered sample. The density was measured by the means of archmedias method. Surface roughness of the sintered samples was measured by Aliconia profilometer.

3. Results and discussion

3.1. Powder characteristics and alloying process

Fig. 1. shows the secondary electron imaging (SEM-SEI) and backscattered images (SEM-BEI) of the ball-milled Ti–10Nb–3Mo powders at the rotation speeds of 200 and 300 rpm without and with the addition of 2 wt.% EBS. The size and morphology of the powder particles (flake-shaped) in the presence of EBS were fairly similar at both rotation speeds. In contrast, the bigger agglomerated particles emerged in the absence of EBS as seen in Fig. 1 (A1 and D1).The rate of cold welding was lowered with the addition of EBS due to its lubricating effect [8]. The lubrication effect of EBS was further increased when the EBS was intervals. It resulted in drastic decrease in the size of powder particles due to the dominance of fracturing over cold welding. As mentioned earlier, the powders also exhibited a relatively equiaxed particle morphology and more uniform distribution of particle size. As can be seen in Fig 2F2, the mechanically-alloyed particles can be achieved with the rotation speed of 300 rpm. It is thought that the higher degree of mechanical alloying at higher rotation speed of 300 rpm is mainly the result of higher impact energy transferred to powder particles momentarily trapped between colliding balls at this rotation speed. By the same token, the mechanical alloying did not occur at the rotation speed of 200 rpm due the low impact energy of the colloding balls on powder particles and the presence of EBS. However, the size of particles decreased alternativley from batch 3 to batch 5 because of the EBS addition. Increasing the uniformity and homogeneity of powder particles with increasing intervals of

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addition of EBS can be correlated to improved lubrication effect led to change in the mechanism of cold welding and fracturing and attain a well-balanced mechanism. Increasing the number of time intervals provides fresh EBS for elemental powders at every stage which decreases both contact area and the local temperature during collisions [9].

Fig. 1. SEM micrographs of the Ti–10Nb–3Mo alloy powders ball milled for 10 h at rotation speed of 200 rpm (A1) without the addition of EBS; and with the addition of 2 wt.% EBS at (B1) 1 interval; and (C1) . Ball milling for 10 h at rotation speed of 300 rpm (D1) without the addition of EBS; and with the addition of 2 wt.% of EBS at (E1) 1 interval; and (F1) s. The associated cross-sectional back scattered electron micrographs of the the powders are shown as A2, B2, C2, D2, E2, and F2.

XRD patterns of the Ti–10Nb–3Mo powder mixtures ball milled at frequency rotation speeds of 200 and 300 rpm for 10 h without and with the addition of 2 wt.% EBS are given in Fig. 2. It can be seen that the peak intensity of elemental powders increases with increasing the

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interval of EBS addition. The addition of surfactants to metal powders minimizes cold welding and promotes fracturing, thus cause a delay in alloying and formation of Ti-based solid solution [6]. All XRD patterns of the ball-milled powders show the diffraction peaks of -Ti and Nb. Nonetheless the diffraction peaks of Mo are absent in the patterns obtained after ball milling at rotation speed of 300 rpm. The diffraction peaks of Nb and Mo are also detectable in the XRD patterns obtained after ball milling at 200 rpm, indicating less degree of alloying at this stage (Fig The absence of Mo peaks at 300 rpm is associated with higher degree of alloying as compared to ball milling at 200 rpm.

Fig. 2. XRD patterns of Ti–10Nb–3Mo powder particles ball milled for 10 h at two rotation speeds, with and without the addition of EBS. B#1: 200 rpm; B#2: 1 interval+200 rpm; B#3: ; B# : 300 rpm: B#5: 1 interval + 300 rpm; B#6: [10].

3. 2. Hardness of sintered compacts

The Vickers microhardness values (HV) of the sintered Ti–10Nb–3Mo alloy are summarized in Table 2. All samples were made under identical sintering conditions. It is noteworthy that the hardness of the sintered samples made from [10]the powders without the addition of EBS) could not be measured due to high level of porosity on the surface of the samples. The results showed that the hardness of the alloy increased for the sintered samples made from the powders of batch 3 and 5. The hardness of the sintered alloy

Inte

nsity

(a.u

.)

(deg.)

Ti-10Nb-3Mo

B#1

B#2

B#3

B#4

B#5

B#6

NbMo

30 40 50 60 70 80 90

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made from the ball-milled powder which EBS added in 1 intervals was distinctly lower than those sample made from the ball-milled powder with the addition of EBS . It is notable that the lowest hardness of 260 HV was reported for sample made from the powders with the addition of EBS at 1 intervals at rotation speed of 200 rpm. The sintered samples made from the powders ball milled at higher rotation speed of 300 rpm showed higher hardness values as compared to their counterparts. It is due to the fact that particles ball milled at higher rotation speed undergo larger plastic deformation, higher work-hardening rate, and solid-solution strengthening. In contrast, higher hardness of samples made from the powders with addition of EBS can be related to the presence of dispersoid particles of TiC during ball milling process [9, 11]. The other reason for the high hardness of batch 6 is because fine particles with more homogeneity can give rise to refinement of microstructure. It is also mostly due to the presence of higher amount of EBS which decomposes into O, C during sintering and give rise to the formation of TiC and TiO2 [11].

Table 2. Micro Vickers hardness of bulk Ti–10Nb–3Mo alloy made from the powders ball milled for 10 h with the addition of 2 wt. .

Sample name Hardness (HV)

200 rpm 300 rpm —-- —---

Batch 2, Batch 5 260 335 Batch 3, Batch 6 300 370

3.3. Density of sintered compacts

The relative density of bulk sintered compacts made from the ball-milled powders with varying rotation speeds and surfactant addition times is listed in Table 3. The relative density shows an upward trend with increasing the number of time intervals. The sintered samples made from the powders ball milled at rotation speed of 200 rpm exhibited higher relative density compared to those made from the powders ball milled at 300 rpm. It is also noticeable that almost full densification close to the theoretical density was obtained in the sintered Ti–10Nb–3Mo alloy made from the powders ball milled at rotation speed of 200 rpm

. The data show that the remaining (undecomposed) EBS in ball milled powders resulted in more lubricating effect and therefore higher compressibility. Increasing the rotation speed to 300 rpm not only led to more decomposition of EBS (indicating that the EBS for 300 rpm has already been decomposed in the ball milled particles), but also resulted in more work-hardened powder particles than 200 rpm. These are the main reasons that the ball-milled powders for 300 rpm show lower compressibility than 200 rpm and thus, less bulk density.

Table 3. The relative density of bulk sintered Ti–10Nb–3Mo alloy made from the powders ball milled for 10 h with the addition of 2 wt.% of EBS at different interval addition.

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Sample name Relative density (%)

200 rpm 300 rpm Batch 1, Batch 91 82 Batch 2, Batch 5 97 89 Batch 3, Batch 6 98 93

3.4. Roughness

The roughness values of the surface of bulk sintered samples are shown in Fig. 3. The surface roughness of the sintered sample prepared from the powders ball milled at 200 rpm is lower than the sample prepared at 300 rpm. It is due to the fact that in the current study higher rotation speeds produced coarser particles which left voids and irregularities on the surface of the material during compaction and after sintering. The highest roughness value was found for the sintered samples prepared from powders ball milled without EBS addition at 300 rpm as comapred to its counterpart prepared with same conditions nm). The roughness values decreased with increasing the EBS intervals showing that there are lower level of porosity and irregularity on the surface when the intervals. The lowest roughness belonged to the sample prepared from

at 200 rpm.

Fig. 3. The surface roughness values of sintered samples prepared from powders ball milled at 200 and 300 rpm ervals.

4. Conclusion

The present study investigated the effect of spliting a surfactant (i.e. EBS) into small weight fractions and adding at regular time intervals for synthesis of biomedical Ti–10Nb–3Mo alloy through ball milling process. Increasing the number of time intervals resulted in smaller particles and change in the powder morphology from flaky- to irregular-type shapes due to

0

100

200

300

400

500

600

700

800

900

Batch 1 Batch 4Without EBS

Batch 2 Batch 5I interval

Batch 3 Batch 64 intervals

Rou

ghne

ss (n

m)

200 rpm

300 rpm

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the suppression of excessive cold welding. Higher hardness and relative density were obtained for the sintered samples made from the powders ball milled with the addition of EBS at regular time intervals. Increasing the number of time intervals and rotation speed decreased the surface roughness of the sintered samples, provided a smoother surface.

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