AUTHOR’S MANUSCRIPT PREPARATION PACKAGE

Properties of Powders, Coatings and

Consolidated Components Produced fromNano- and Near-Nano Crystalline PowdersD. Grant, S. Schroeder, C. MelnykCalifornia Nanotechnologies, Cerritos, California, USAG. Saha, L. GleneskHyperion Technologies Inc., Calgary, Alberta, Canada

R. GansertAdvanced Materials & Technology Services, Inc, Simi Valley, California, USAAbstract

Instructions from author kit - You would begin typing your actual manuscript here, after typing in your first heading. But, before you do anything, you should print this page and use it as a guide to align your actual manuscript first page. Your abstract would be written as one paragraph and not contain figures. A common error in the past has been to forget to use “Title Case” for the paper title, as shown above. Please take time to ensure this has been done correctly. Please do not use “Sentence case” for the paper title. For the authors’ affiliation, include only the information shown in the example (above). Do not include street addresses, postal or country codes, or telephone numbers. Include the e-mail address only for the contact author.

Introduction

We will put together a nice introductory paragraph to nano that fits with our theme of this paper we are writing…..

Nanocrystalline Strengthening

David, Chris, Steven, Gobinda and Laryy……

I am proposing we have this section on on nano- and near nano materials using cryomilling technique…………Cryomilled materials are known to provide property improvements as a result of grain refinement through the cryomilling process as well as the formation of nitrides through milling in the liquid nitrogen environment blah blah. This will provide a nice background on much of the work behind the cryomilling processing to produce nano materials…

Figure 1 shows the increase in nitrogen content in an Al-Mg based alloy as a function of the milling time. The original carbon and hydrocarbon content in the as-supplied powder remains at approximately the same percentages during the milling.

Figure 1: Nitrogen Wt. % vs. Milling Time

The cryomilling provides both grain refinement as well as the formation of metal-nitrides. In Fig. 2 is shown a transmission electron microscopy (TEM) imaging of an aluminum-nitride (AlN), on the order of 8-10 nm in diameter by approximately 1 nm in thickness.

Figure 2: TEM image of Aluminum Nitride (AlN) formed in the cryomilling processof Al-Mg based alloy

The properties of the original materials are greatly improved through the use of the cryomilling process. The grain refinement and introduction of nitrides bring the properties in the realm of those of other material systems. As shown in the well-known Asby Maps in Fig. 3. The cryomilled Al-Mg based material exhibits the specific strength and specific stiffness of conventional titanium-based alloys. Similarly, the operating service temperature of the Al-Mg based material allows much higher service temperature than a conventional Al-Mg alloy would allow.

Figure 3:Specific Strength and Specific Stiffness of cryomilled Al-Mg based material in the envelop of titanium alloys

Experimental Approach

Aluminum, commercially pure (CP) titanium, aluminum-6 wt.% titanium, cobalt-chromium based superalloy and tungsten carbide-cobalt-chromium powders are cryogenically milled in a high energy, ball mill attritor to the parameters shown in table 1.

A Szegvari milling machine, model S1 (Union Process, New Jersey?) was modified for liquid nitrogen use. Stainless steel balls …..

Table 1. Typical Cryogenic Milling Parameters

Element

Powder Weight (kg)

Typical 1 kg

Milling Time (hrs.)

8, 12, or 24 hrs.

Media

Liquid Nitrogen

Balls (Material, Diameter)

Stainless Steel, ¼” diameter

These materials are subsequently processed using a variety of methods including thermal spray, hot isostatic pressing (HIP) and spark plasma sintering (SPS).

The thermal spray techniques are well documented [x,y,z]. High velocity oxy-fuel (HVOF) spraying is commonly performed for WC-carbide based powder materials. Plasma spraying the aluminum is performed using a Sulzer Metco 7M system (Sulzer Metco, Westbury, NY).

Bulk consolidation processing was conducted using HIP and SPS processing. The processing parameters for hot isostatically pressed, cryomilled aluminum-titanium, CP titanium and Co-Cr based superalloy are provided in Table 2.

Table 2. Hot Isostatic Pressing

Element

Al-6%Ti

CP Ti

Co-Cr based super alloy

Consolidation Temperature

xyz°F

(talk to Steven & Chris)

850°F

(talk to Steven & Chris)

xyz°F

(reference

Publ. work)

Consolidation

Pressure

15 ksi

15 ksi

15 ksi

(reference publ. wrok)

Spark plasma sintering was conducted using Dr. Sinter 1050 SPS apparatus (Sumitomo Coal Mining Co., Japan). Graphite punches and dies were used to produce disks 30 mm diameter and 5 mm in height. A type-K thermocouple was inserted into the die wall to monitor temperature and the die was covered with a carbon felt 5 mm thick. In SPS, the powder is placed in a graphite die and pressed uniaxially while a pulsed electric current is applied through the graphite punches. Sintering experiments were conducted conducted in the temperature range of 700°-1150°C for 5-10 minutes, under a uniaxial pressure of 60 MPa, in vacuum.

Table 3. Spark Plasma Sintered Powders

Element

Al

1100

Al-

6%Ti

CP

Ti

Co-Cr-based Superalloy

WC-Co-Cr

Temperature (°F)

xyz

xyz

xyz

xyz

xyz

Pressure (ksi)

xyz

xyz

xyz

xyz

xyz

Time at

Temp. (min.)

xyz

xyz

xyz

xyz

xyz

Microstructural analysis was performend using a JEOL 7000 Field Emission Scanning Electron Microscope (JEOL, xyz, Japan). Density was measured by the water displacement method. Hardness (HV300) was measured using a xy (City, State). Hardness measurements were carried out taking five indentations on each specimen. Nitrogen analysis was measured using a LECO TC-436 machine (City, State). Wear testing was conducted using a Falex (City, State) abrasion testing machine and samples were tested to ASMT G-65.

Results

{NOTE to David Chris, and Steven – The intent of the first part of the results is to paint a clear picture to the readers is that “nanocrystalline” powders used in consolidation, HIP and SPS, clearly show property improvements over bulk material (virgin) properties – thus reason we are even working in the field}.

{The second part of the results section is then follows with this argument (property improvements from nano) to imply (and show results where we can) that the coatings likewise benefit from the cryomilling improvements}

SEM images of the virgin feedstock and cryomilled powders are shown in Figs. 4-5.

Fig. 4a,b (virgin, cryomilled Al)

Fig. 5a,b (virgin, cryomilled Al-6%Ti)

Fig. 6a,b (virgin, cryomilled CP Ti)

Fig. 7a,b (virgin, cryomilled

Co-Cr based Superalloy)

Fig. 8a,b (virgin, cryomilled WC-Co-Cr)

Grain refinement of the metallic grains is evident in all the metals as shown in the metallographs in Figs. 4-7. A layered structure is provided by metal grains being milled and microwelded onto the previous clad layer………..etc. In Fig. 8, the cryomilling results for WC grains shows a different effect. The cryomilling with carbides, as well as other ceramics, results in attrition of the particles to nano- and near-nano grains without the characteristic agglomerating of the metallic particles.

In Fig. 9, xyz alloy is shown SEM images as a function of milling time.

9 (a) 9 (b)

Fig. 9a,b,c,d (SEM images of virgin, cryomilled x at a,b and c hrs.)

The xyz grains decrease in size from micron size grains to less grains less than 100 nm, occuring in x hours. In Fig. 10, elemental mapping of the material shows the x and y elements at the grain boundary. This information along with the nitride content (Fig. 1) indicates the formation of x and y nitrides at the grain boundaries.

10 (a) 10 (b)

10 (c) 10 (d)

Fig. 10a,b,c,d (Elemental mapping of virgin, cryomilled X,Y and Z hrs.)

The results of the HIPed cyromilled materials are provided in Tables 4.

Table 4. HIP Testing on virgin and cryomilled Aluminum, Aluminum-Titanium and CP Titanium

Element

Hardness

(HVN)

Ultimate Shear Strength (ksi)

Virgin Al

xyz

xyz

Cryomilled Al

xyz

xyz

Virgin Al-6% Ti

xyz

xyz

Cryomilled Al-6% Ti

xyz

xyz

Virgin CP Ti

xyz

Xyz

Cryomilled CP Ti

xyz

94.0 (S. Keener paper)

The hardness and ultimate shear strength of the cryomilled aluminum, aluminum-titanium and CP titanium are all greater than the properties of the virgin materials indicate the indicating the strengthening and hardness increases associated with grain refinement and metal-nitride formation.

The results of the spark plasma sintered cryomilled materials are provided in Table 5.

Table 5. SPS Testing on virgin and cryomilled Aluminum, Aluminum-Titanium and CP Titanium

Element

Hardness

(HVN)

Ultimate Shear Strength (ksi)

Virgin Al

xyz

xyz

Cryomilled Al

xyz

xyz

Virgin Al-6% Ti

xyz

xyz

Cryomilled Al-6% Ti

xyz

xyz

Virgin CP Ti

xyz

xyz

Cryomilled CP Ti

xyz

Xyz

SEM analysis of cross-sectioned samples of virgin CP Ti (or Al-6% Ti for example or another material Cal Nano desires to use) powder and shows the bonding of adjacent grains in Figs.

Fig. 11a Fig. 11b

Fig. 11 a and b (SEM images of cross-sectioned SPS samples of virgin, cryomilled xy material)

The hardness and ultimate shear strength of the cryomilled aluminum, aluminum-titanium and CP titanium are all greater than the properties of the virgin materials indicate the indicating the strengthening and hardness increases associated with grain refinement and metal-nitride formation. It can be seen in the cryomilled materials the nano and near-nano grains. The SPS sintering technique maintains the nano-structure of the as-supplied feedstock

Thermal spray processing of virgin and cryomilled powder was performed by California Nanotechnologies, Inc. (Cerritos, CA.) and Hyperion Technologies, Inc. (Calgary, Alberta, Canada). Series 1100 Aluminum was sprayed using a Sulzer Metco 7M plasma spray system, and WC-Co-Cr was sprayed with a Sulzer Metco Diamond Jet HVOF system.

Micrographs of the thermal sprayed Al series 1100 and WC-Co-Cr are provided in Figs. 12a, and 12b.

12 (a) 12 (b)

12 (c) 12 (d)

Fig. 12 a,b,c,d (SEM images of cross-sectioned thermal sprayed samples of virgin, cryomilled Al and WC-Co-Cr)

The microhardness and macrohardness of the thermal sprayed samples of the virgin and cryomilled powders are reported in Table

Table 6. Microhardness and Macrohardness of thermal sprayed virgin and cryomilled Aluminum and WC-Co-Cr

Element

Micro-hardness

(HVN)

Macro-hardness

(units?)

Virgin Al

xyz

xyz

Cryomilled Al

xyz

xyz

Virgin WC-Co-Cr

xyz

xyz

Cryomilled WC-Co-Cr

xyz

xyz

An increase is observed in both the microhardness and macrohardness testing of the thermally sprayed Al and WC-Co-Cr coatings.

In research conducted by Hyperion, microcrystalline WC-Co and near-nano WC-17%Co powders were sprayed to compare the properties improvements of the nano-crystalline grains [ref xy]. Micrographs of the HVOF coatings are provided in Figs. 13a and 13b

10 (c) 10 (d)

Fig. 12 a,b,c,d (SEM images of cross-sectioned thermal sprayed samples of virgin, cryomilled Al and WC-Co-Cr)

Table 7. Microhardness and Wear Resistance of thermal sprayed HVOF spray microcrystalline WC-Co(Cr) and WC-17%Co

Material

CS AISI

1018

C-Mn

Hard. Steel

HVOF

WC-Co(Cr)

HVOF WC-17%Co

Hardness (HVN)

230

348

1048

1440

Wear Rate

5.21

4.72

0.28

0.203

Wear Rate %

-

-

-

72%

An increase is microhardness and wear resistance is observed in the nano-crystalline sprayed WC-Co-Cr coatings.

Discussion

David, Steven, Chris, Gobinda and Larry…The discussion section is used to describe the results of the previous section…. I am leaving this blank until Cal Nano & Hyperion decides which samples above they are in-fact using for this paper etc.

The following are instructions for manuscript writing that I’ve left in for everyone to see. This will obviously be deleted as we write the paper but did want to leave this in for everyone to see….

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3.J. Sickfield, Pull-off Test, Adhesion Aspects of Polymeric Coatings, 2nd ed., K.L. Mittal, Ed., Sept 15-18, 1980 (Paris), Plenum Press, 1983, p 543-567

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