Processing P/M Components to High Density Using an Advanced
Lubricant/Binder System
George Poszmik & Michael L. Marucci
Hoeganaes Corporation, Cinnaminson, NJ
Presented at PM2TEC2005
International Conference on Powder Metallurgy and Particulate Materials
June 19-23, 2005 • Montréal
ABSTRACT
The recent introduction of a high-density lubricant system enables the processing of
ferrous P/M components to up to 98% of pore-free density when using a heated
compaction tool. This system, AncorMax D, uses proprietary lubricants that enable the
total organic content of a P/M premix to be reduced while maintaining comparable
ejection characteristics. This results in the ability to compact components to higher green
densities (up to 7.40 g/cm3) using higher compaction pressures. This paper outlines
production experience using this advanced system.
INTRODUCTION
The creation of new products with better quality and higher performance through the
development of new materials and technologies has made it possible for the P/M industry
to achieve steady growth over the years. Especially important are processes and products
that allow the manufacturer of P/M parts to reach higher green and sintered densities in a
single press/single sinter operation.
A recent development in this area is a high density lubricant/binder system, AncorMax D,
that can reach green densities up to 7.40 g/cm3 at 140°F to 160°F (60°C to 71°C) die
temperature and 50 tsi to 60 tsi (690 MPa to 830 MPa) compaction pressure [1, 2, 3].
Preheating the iron powder is not required with this technology. This technology allows
for the reduction of organic material within the premix to increase the pore free density,
but maintains a good level of lubrication. One limitation of the system is that it can be
used on parts with overall lengths of about 0.75 in (19 mm). Improvements in the
AncorMax D system have been developed that allows the processing of longer parts, up
to 1 in to 1.25 in (25 mm to 32 mm) depending on the complexity of the part, with a
lower total organic content (0.50 vs. 0.55 w/o). This paper discusses the physical and
mechanical properties together with production experience using this advanced system.
EXPERIMENTAL PROCEDURES
Materials
The testing was carried out on FLN2-4405 premixes made with Ancorsteel 85HP*, a base
iron prealloyed with 0.85 w/o Mo that was admixed with 0.6 w/o graphite (Asbury 3203)
and 2.0 w/o nickel (INCO 123). Two test mixes were prepared, one with 0.5 w/o
AncorMax D and one with 0.75 w/o EBS (Acrawax C). The mixes were made as 500 lbs
(227 kg) mixes with compositions listed in Table I. Note that the AncorMax D mix is a
fully bonded material, where the mix with EBS is a standard premix.
TABLE I: Compositions of the Powders Evaluated
Designation
AncorMax D
EBS
Base Material (w/o)
Fe
Mo
Balance
0.85
Balance
0.85
Ni
2.00
2.00
Elemental Additions (w/o)
Graphite
Lube & Binder
0.60
0.50 w/o AncorMax D
0.60
0.75 w/o EBS
Testing
A Tinius-Olsen hydraulic press was used for pressing the compressibility samples with a
heated die that maintained temperature at 145°F (63°C). Compaction of test samples was
performed between 40 tsi and 60 tsi (550 MPa and 830 MPa). All testing was performed
in accordance with MPIF standards [4].
Green properties and ejection pressures were determined on test bars measuring 1.25 in
(32 mm) x 0.5 in (13 mm) x 0.5 in (13 mm).
Sintered properties were carried out on standard transverse rupture samples (TRS)
pressed as listed above. The samples were subsequently sintered at 2050°F (1120°C) in
an atmosphere consisting of 90 v/o N2 – 10 v/o H2.
Production press trials were performed on a 220 ton Cincinnati mechanical compaction
press. The die was preheated to 120°F (48°C). No powder heating was used. Bushings
1.5 in (38.1 mm) OD x 1.0 in (25.4 mm) ID were compacted to an overall length of 1.0 in
(25.4 mm). Compaction was done at 55 tsi (760 MPa) and the press rate was 10
parts/min.
RESULTS AND DISCUSSION
Compressibility & Ejection Characteristics
Figure 1 shows a comparison of the compressibility of the two materials evaluated. Note
that under the same pressing conditions the AncorMax D results in green densities that
are 0.05-0.15 g/cm3 higher than the standard EBS premix. Also, note that the density
*
Ancorsteel and AncorMax D are trademarks of Hoeganaes Corporation.
difference is more pronounced at higher compaction pressures. There is little benefit
from the high-density lubricant binder system below 40 tsi (550 MPa).
Compaction Pressure (MPa)
480
550
620
690
760
830
900
Green Density (g/cm3)
7.40
7.35
AncorMax D
7.30
7.25
EBS
7.20
7.15
7.10
7.05
35
40
45
50
55
60
65
Compaction Pressure (tsi)
Figure 1:
Compressibility of FLN2-4405 with high-density lubricant/binder system and standard EBS
premix. Compaction die preheated to 145°F (63°C).
In addition to the higher green density that is achieved, the high-density lubricant/binder
system also has superior ejection characteristics. Table II show a comparison of green
properties for both test materials compacted at over a range of densities. The data show
that even with the higher density, the ejection pressures (Strip and Slide) are lower for the
AncorMax D. One interesting feature of the high-density lubricant/binder system is that
the sliding pressure decreases as compaction pressure goes up. This may explain the
ability for density to keep rising without forming green cracks.
TABLE II: Green Properties of Test Materials
Material
AncorMax D
EBS
Green
Density
(MPa) (g/cm3)
7.13
550
7.30
690
7.34
760
7.37
830
7.08
550
7.21
690
7.24
760
7.26
830
Pressure
(tsi)
40
50
55
60
40
50
55
60
Green
Strength
(psi) (MPa)
1868 12.9
2300 15.9
2397 16.5
2397 16.5
2191 15.1
2349 16.2
2352 16.2
2347 16.2
Strip
(psi)
3418
3609
3602
3570
3595
4327
4259
4223
(MPa)
23.6
24.9
24.8
24.6
24.8
29.8
29.4
29.1
Slide
(psi)
1898
1686
1531
1428
2075
2540
2516
2617
(MPa)
13.1
11.6
10.6
9.8
14.3
17.5
17.4
18.0
Sintered Properties
The sintered density of FLN2-4405 with both lubricant systems is shown in figure 2. The
presence of Ni in this alloy causes a net shrinkage during sintering and the density
increases slightly. At the highest compaction pressure the sintered density reaches 7.40
g/cm3. The TRS increases with the higher density. Examination of figure 3 shows that
TRS generally increases with density independent of lubricant system. It is also notable
that at 60 tsi (830 MPa) the strength of the 0.75 w/o EBS version drops. This is caused
by laminations introduced from over compacting this material that has a higher organic
content and a lower pore free density.
Compaction Pressure (MPa)
480
550
620
690
760
830
900
Sintered Density (g/cm3)
7.45
7.40
AncorMax D
7.35
7.30
7.25
EBS
7.20
7.15
7.10
7.05
35
40
45
50
55
60
65
Compaction Pressure (tsi)
Figure 2:
Sintered density of FLN2-4405 with high-density lubricant/binder system and standard EBS
premix. Sintered at 2050°F (1120°C).
250
240
1630
220
1530
210
1430
200
1330
190
180
TRS (MPa)
TRS (103 psi)
230
1230
170
1130
160
150
7.00
1030
7.10
7.20
7.30
7.40
7.50
Sintered Density (g/cm3)
Figure 3:
Transverse rupture strength (TRS) of FLN2-4405 with high-density lubricant/binder system
and standard EBS premix. Sintered at 2050°F (1120°C).
Production Press Test Results
The mixes were evaluated on a Cincinnati 220 ton mechanical press by pressing 500
cylinders with 1.5 in OD and 1.0 in ID. The rings had an over all length (OAL) of 1 in.
The die was preheated to 120°F (49°C) and the parts were pressed at 55 tsi (760 MPa) at
10 parts per minute rate. Weight was measured for every fifth part and surface
temperature was measured for every fiftieth part. Figure 4 shows the weight variation for
the modified AncorMax D mix and Figure 5 for the EBS mix.
The modified AncorMax D mix gave a slightly tighter weight control, with a standard
deviation of 0.216 g versus 0.223 g for the Acrawax mix. Green densities were 7.24
g/cm3 versus 7.18 g/cm3 and sintered densities were 7.32 g/cm3 and 7.22 g/cm3 for the
two mixes respectively. The standard deviation between the measured density values
was slightly lower for the high-density lubricant system.
126.0
0.5 w/o AncorMax D
125.5
Min: 123.34 g
Max: 124.49 g
Range: 1.15 g
Stdev: 0.216 g
125.0
Mass (g)
124.5
124.0
123.5
123.0
122.5
122.0
0
50
100
150
200
250
300
350
400
450
500
Part Number
Figure 4:
Weight variation of FLN2-4405 bushings using the AncorMax D system. Compaction die
preheated to 120°F (49°C), compacted at 55 tsi (760 MPa).
120.0
0.75 w/o EBS
118.0
116.0
Mass (g)
114.0
112.0
Min: 114.27 g
Max: 115.26 g
Range: 0.99 g
Stdev: 0.223 g
110.0
108.0
106.0
104.0
102.0
100.0
0
50
100
150
200
250
300
350
400
450
500
Part Number
Figure 5:
Weight variation of FLN2-4405 bushings using EBS. Compaction die preheated to 120°F
(49°C), compacted at 55 tsi (760 MPa).
Ejection forces were virtually equal for both materials. Part surface temperatures varied
between 148°F (64.4°C) and 156°F (68.9°C) for the AncorMax D and between 155°F
(68.0°C) and 162°F (72.2°C) for the Acrawax mix. This difference in part surface
temperature indicates lower ejection pressure and better lubricity for the test mix.
TABLE III: Green and Sintered Densities of FLN2-4405 Bushings
Compaction die preheated to 120°F (49°C), compacted at 55 tsi (760 MPa), Sintered at 2050°F (1120°C)
Material
AncorMax D
EBS
Green
Density
Green
Density
Standard
Deviation
Sintered
Density
Sintered
Density
Standard
Deviation
(g/cm3)
7.24
7.18
(g/cm3)
0.006
0.008
(g/cm3)
7.32
7.22
(g/cm3)
0.005
0.007
The surface of bushings pressed using the high-density lubricant/binder system and 0.75
w/o EBS are shown in Figures 6 and 7, respectively. Comparison of the SEM
micrographs show that the average pore size for the higher density compact is smaller
than the EBS version, as expected. The number and severity of score marks present in
the AncorMax D sample is less than in the EBS sample. The EBS part surface also has
scale marks caused by a breakdown in lubricant. These defects are not present in the
AncorMax D version. Overall, the surface quality is better for the high density
lubricant/binder system.
Figure 6:
SEM photomicrograph of the surface finish of
FLN2-4405 bushings using AncorMax D.
Compaction die preheated to 120°F (49°C),
compacted at 55 tsi (760 MPa), 10 parts/min.
Figure 7:
SEM photomicrograph of the surface finish of
FLN2-4405 bushings using 0.75 w/o EBS.
Compaction die preheated to 120°F (49°C),
compacted at 55 tsi (760 MPa).10 parts/min.
CONCLUSIONS
•
•
•
•
When processed under the same compaction conditions, the AncorMax D
produces a green density that is 0.05-0.15 g/cm3 higher than a conventional EBS
premix.
The ejection pressures are lower for AncorMax D at 7.37 g/cm3 than the EBS mix
at 7.25 g/cm3.
The weight control and ejection characteristics of bushings prepared with both
materials tested are similar, even with the significant difference in green density.
The surface finish of samples pressed with the high-density lubricant/binder
system contains less scoring and a lower degree of scale like defects than an EBS
mix pressed under the same conditions.
REFERENCES
1.
2.
3.
4.
Donaldson, I.W., Luk, S.H., Poszmik, G., Narasimhan, K.S., “Processing of
Hybrid Alloys to High Densities”, Advances in Powder Metallurgy & Particulate
Materials – 2002, Part 8, pp 170-185, Metal Powder Industries Federation,
Princeton, NJ.
Poszmik, G., Luk, S.H., “Binder Treated Products for Higher Densities and Better
Precision”, Advances in Powder Metallurgy & Particulate Materials – 2003, Part
3, pp 33-44, Metal Powder Industries Federation, Princeton, NJ.
Poszmik, G., Marucci, M. L., Narasimhan, K.S., “Single Pressed Single Sintered
P/M Products for High Density, High Performance Applications”, 2004 World
Congress on Powder Metallurgy and Particulate Materials (PM2004), Vienna,
Austria.
“Standard Test Methods for Metal Powders and Powder Metallurgy Products”’
Metal Powder Industries Federation, Princeton, NJ, 2003.