HIGH PERFORMANCE MATERIALS – ANCORLOY MD SERIES
Suresh O. Shah,
HazenTec, Hazen, Arkansas
Michael C. Baran, Sunil N. Patel, and Robert J. Causton
Hoeganaes Corporation, Cinnaminson, NJ
Presented at PM2TEC 2001
International Conference on Powder Metallurgy & Particulate Materials
May 13 – 17, 2000 New Orleans, LA USA
ABSTRACT
New silicon-containing materials were recently introduced to compete with various grades of
ductile and malleable cast irons. These binder-treated, press-ready premixes offer extremely
good physical and mechanical property combinations. This work focuses on the evaluation of
these materials in a production environment. Properties such as impact energy, tensile
strength, elongation, dimensional change and apparent hardness are presented.
INTRODUCTION
As the P/M industry strives to convert higher performance parts from cast irons and wrought
steels, increasingly stringent requirements necessitate modifications to existing material
systems. In the past, the part manufacturers’ options were somewhat limited. Manufacturing
capabilities were improved by increasing density, admixing or prealloying more expensive
alloying additions, and/or redesigning parts. However, higher processing and material costs
reduced the attractiveness of the first two options, while inflexible customer or enduser
specifications often excluded the consideration of the third. In an effort to satisfy their desire
to convert demanding parts, the part manufacturers and OEMs issued a challenge to ferrous
powder producers – develop a material or family of materials that can:
(1) Economically achieve high performance targets,
(2) Combine high strength with reasonable ductility and impact energy, and / or
(3) Offer the opportunity to reduce manufacturing operations. For example, convert a
double press / double sinter (DP/DS) operation to single press / single sinter
(SP/SS) process.
In 2000, a series of materials were introduced to address this challenge [1,2]. These
®
materials, Ancorloy MDA, Ancorloy MDB, and Ancorloy MDC, were specifically engineered to
replace malleable and ductile cast irons. This family of materials has been shown to exhibit
tensile strengths of 450 – 1250 MPa, elongations of 2 – 4%, impact energies of 10 – 28
Joules, and apparent hardness values of 70 HRB – 45 HRC. The potential market for P/M
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parts with cast iron properties is vast and could offer lucrative high volume opportunities to the
P/M industry.
Ductile iron is used in applications such as crankshafts because of its (a) good machinability,
(b) fatigue strength, and (c) high modulus of elasticity; in heavy-duty gears because of its
(a) high yield strength and (b) wear resistance; and in automobile door hinges because of its
ductility [3]. Since it contains magnesium as an alloying element, ductile iron is stronger and
more shock resistant than gray iron.
The three basic types of malleable iron are ferritic, pearlitic, and martensitic. Ferritic grades
are more machinable and ductile, whereas the pearlitic grades are stronger and harder. The
martensitic grades are thought of as higher strength extensions of pearlitic malleable iron.
Malleable iron castings are often used for heavy-duty bearing surfaces in automobiles, trucks,
railroad rolling stock, and farm and construction machinery. Pearlitic grades are highly wear
resistant, with hardness values ranging from 80 HRB to over 32 HRC. Applications are limited,
however, to relatively thin-sectioned castings because of the high shrinkage rate and the need
for rapid cooling to produce white iron.
BACKGROUND
The use of silicon in P/M materials can be highly beneficial. In addition to its relatively low cost
and tendency to increase hardenability, it can accelerate sintering in hybrid alloys and
substantially impact mechanical properties [4]. However, despite the inherent metallurgical
advantages of silicon, its use in P/M has been largely unsuccessful in the past. The difficulties
associated with conventional methods of silicon addition are numerous. For example, the
addition of ferrosilicon almost invariably leads to a high degree of shrinkage and distortion in a
P/M compact. Oxidation of silicon during sintering frequently results in an undesirable decline
in mechanical properties. Similar problems are experienced in prealloyed powders. Silicon
oxide pickup during atomization and/or annealing can lead to lower compressibility and
diminished mechanical performance.
Through advancements in atomizing, annealing, and binder-treatment technology, new siliconbearing materials have been developed to provide exceptional property combinations without
large quantities of expensive admixed additions such as nickel, copper, etc. Additionally,
production experience has indicated that these materials exhibit higher mechanical properties
than diffusion-alloyed materials without the production costs associated with diffusion alloying.
In practice, the use of higher performance materials in part production can reduce the
processing steps required for that part. This reduction can minimize variation (especially when
heat treatment can be avoided), curtail costs, and offer a more robust part/process to the
customer. Although HazenTec’s manufacturing capabilities have allowed it to secure a very
demanding automotive part for the P/M industry, the company was extremely interested in
reducing costs and offering added value to their customer. The part is fairly complex with an
overall height exceeding 38 mm. Both the current and proposed production processes are
illustrated in Figure 1.
EXPERIMENTAL PROCEDURE
Two press ready, binder-treated materials, Ancorloy MDB and Ancorloy MDC, were tested in a
production environment in order to evaluate mechanical properties achieved through a SP/SS
process.
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Current Process
Proposed Process
Compact
Compact
Presinter
High
Temperature
Sinter
Repress
Temper
High
Temperature
Sinter
Heat Treat
Temper
Figure 1: A Comparison of the Current Production Process and Proposed Process for the
Demanding Automotive Application Considered in this Study
A third material, denoted as “standard”, was utilized in order to determine the effect of silicon in
a FLNx-4405 type composition, where x is equal to 2 or 4. The “standard” material is the
current composition utilized for this demanding automotive application. Chemical compositions
for all tested materials are listed in Table I. Test and production specimens were produced at
HazenTec from production lots of 4,550 kg (10,000 lb). Although the ideal objective of this
work would be to replace a DP/DS process with a SP/SS one, all testing enumerated in this
work was performed on SP/SS specimens and parts.
Tensile tests were conducted on standard dog-bone tensile specimens. Whenever possible,
compaction pressure was adjusted to maintain consistent green densities.
All test pieces were sintered at HazenTec in a production loaded, high temperature, pusher
furnace. The sintering / tempering cycle used for specimens was as follows:
Sintering Temperature:
Atmosphere:
Time in Hot Zone:
Cooling:
Tempering:
Various (from 1230 – 1315 °C)
80 v/o N2 , 20 v/o H2
45 minutes
Standard Water-Jacketed Section
205 °C for 1 hour in Air
Apparent hardness measurements were performed on the surface of the specimens using a
Rockwell hardness tester. All measurements were conducted on the Rockwell B or C scale
(HRB or HRC). Transverse rupture strength was measured according to ASTM B 528. Impact
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energies were determined according to ASTM E 23. Tensile testing was performed on a 267
kN Tinius Olsen universal testing machine at a crosshead speed of 0.635 millimeters/minute.
Elongation values were determined by utilizing an extensometer with a range of 0 to 20%. The
extensometer was left on until failure. All specimens were tested in the as-tempered condition.
Dimensional change was determined per ASTM B 610 by measuring the major outer diameter
of the production part.
RESULTS AND DISCUSSIONS
Powder Properties and Chemistries
The powder properties of interest were apparent density, flow, and chemical composition.
These properties are presented in Table I. In the scope of this investigation, “standard” refers
to the premix composition used in the current application. As can be seen, the flows and
apparent densities of MDB and MDC do not represent a significant departure from similar “high
performance” materials.
Table I: Chemical Compositions, Apparent Density, and Hall Flow for Material Grades Tested
Grade
“Standard”
FLN4-4405
MDB
MDC
AD
(g/cm3)
Flow
(s/50g)
Fe
(w/o)
Si
(w/o)
Cr
(w/o)
Mn
(w/o)
Ni
(w/o)
Mo
(w/o)
Gr
(w/o)
3.30
28
Bal.
--
0.03
0.13
4.0
0.85
0.6
3.19
3.25
28
28
Bal.
Bal.
0.7
0.7
0.03
0.03
0.13
0.13
2.0
4.0
0.85
0.85
0.6
0.6
Mechanical Properties
A great deal of data was collected during the course of several production trials. In the interest
of brevity, only key data was organized and presented in this paper. Mechanical properties are
listed in Tables II-IV.
It was immediately evident that the tempered densities of both MDB and MDC were lower than
the standard material used in the study. Nonetheless, these materials were found to be
competitive with or vastly superior to the FLN4-4405 composition that was traditionally used for
this application. Despite its lower nickel content (2 w/o vs. 4 w/o), MDB may offer a more
economical alternative to the standard material. MDC, on the other hand, was capable of
easily outperforming the “standard” in almost every respect – apparent hardness, TRS, impact
energy, ultimate tensile strength, and yield strength. Furthermore, no decrease in ductility was
observed with this exceptional increase in properties.
Dimensional Change
From a production standpoint, it was felt that mechanical properties without dimensional
control were of little use to the industry. Hence, the effort to determine dimensional change
and its variation was undertaken. The tempered dimensional change values for the materials
studied can be found in Figure 2 and Table V. The data illustrate that MDB and MDC exhibited
a lower degree of shrinkage than the “standard” material at every sintering temperature
considered. More importantly, the dimensional change ranges were much tighter in the
Ancorloy materials. As evidenced in Table V, the total dimensional change range for MDC
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represented a 75% reduction from the range exhibited by the FLN4-4405 composition (0.07%
vs. 0.28%). This tighter dimensional control became increasingly significant when the size and
complexity of the part were considered. In all cases, dimensional change, as determined by
the measuring the major outer diameter of the part, was in the range of –0.0015 to –0.0080
mm/mm.
Table II: As-Tempered TRS Properties of All Materials Utilizing Various Sintering
Temperatures
Grade
“Standard”
FLN4-4405
MDB
MDC
Sintering
Temperature
(°C / °F)
Density
(g/cm3)
TRS
(MPa / 103 psi)
Apparent
Hardness
(HRB / C)
1230 / 2250
1260 / 2300
1285 / 2350
1315 / 2400
1230 / 2250
1260 / 2300
1285 / 2350
1315 / 2400
1230 / 2250
1260 / 2300
1285 / 2350
1315 / 2400
7.13
7.12
7.13
7.16
6.96
7.04
7.03
7.05
7.03
7.07
7.08
7.09
1675 / 245
1675 / 245
1730 / 250
1835 / 265
1540 / 225
1580 / 230
1675 / 245
1730 / 250
2060 / 300
2165 / 315
2340 / 340
2370 / 345
95 HRB
94 HRB
95 HRB
95 HRB
91 HRB
93 HRB
94 HRB
94 HRB
28 HRC
32 HRC
32 HRC
34 HRC
Table III: As-Tempered Impact Properties of All Materials Utilizing Various Sintering
Temperatures
Grade
“Standard”
FLN4-4405
MDB
MDC
Sintering
Temperature
(°C / °F)
Density
(g/cm3)
Impact Energy
(J / ft.lbf)
Apparent
Hardness
(HRB / C)
1230 / 2250
1260 / 2300
1285 / 2350
1315 / 2400
1230 / 2250
1260 / 2300
1285 / 2350
1315 / 2400
1230 / 2250
1260 / 2300
1285 / 2350
1315 / 2400
7.14
7.09
7.13
7.14
6.97
7.01
7.03
7.00
7.01
7.05
7.04
7.06
22 / 16
19 / 14
20 / 15
20 / 15
20 / 15
23 / 17
27 / 20
30 / 22
24 / 18
30 / 22
33 / 24
34 / 25
94 HRB
94 HRB
96 HRB
98 HRB
89 HRB
93 HRB
93 HRB
94 HRB
32 HRC
32 HRC
32 HRC
38 HRC
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Table IV: As-Tempered Tensile* Properties of All Materials Utilizing Various Sintering
Temperatures
Grade
Sintering
Temperature
(°C / °F)
Density
(g/cm3)
Ultimate
Strength
(MPa /
103 psi)
Yield
Strength
(MPa /
103 psi)
“Standard”
FLN4-4405
1230 / 2250
7.20
770 / 110
565 / 80
1260 / 2300
7.21
855 / 125
625 / 90
1285 / 2350
7.24
825 / 120
625 / 90
1315 / 2400
7.26
875 / 125
625 / 90
MDB
1230 / 2250
7.02
725 / 105
510 / 75
1260 / 2300
7.07
745 / 110
550 / 80
1285 / 2350
7.09
745 / 110
515 / 75
1315 / 2400
7.10
765 / 110
545 / 80
MDC
1230 / 2250
7.13
1015 / 150
745 / 110
1260 / 2300
7.14
1075 / 155
780 / 115
1285 / 2350
7.16
1125 / 165
840 / 120
1315 / 2400
7.14
1180 / 170
860 / 125
*All tensile properties were collected using dogbone type specimens
Elong.
(%)
Apparent
Hardness
(HRB / C)
1.6
1.9
1.9
1.9
1.8
1.7
2.1
2.2
1.7
1.8
1.8
2.0
97 HRB
97 HRB
97 HRB
97 HRB
94 HRB
93 HRB
93 HRB
94 HRB
34 HRC
34 HRC
34 HRC
36 HRC
0.00
-0.10
-0.20
Dimensional Change (%)
Ancorloy MDB
-0.30
-0.40
Ancorloy MDC
-0.50
-0.60
-0.70
FLN4-4405
-0.80
-0.90
-1.00
1200
1220
1240
1260
1280
1300
1320
1340
Sintering Temperature (°C)
Figure 2: Dimensional Change Variations for All Materials Over a Wide Range of Sintering
Temperatures
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Table V: Tempered Dimensional Change from Die Size of the Actual Production Part
Collected Over a Wide Range of Sintering Temperatures (1230 – 1315 °C)
Grade
1230 °C /
2250 °F
D.C. (%)
1260 °C /
2300 °F
D.C. (%)
1285 °C /
2350 °F
D.C. (%)
1315 °C /
2400 °F
D.C. (%)
Total D.C. Range*
(%)
“Standard”
FLN4-4405
-0.52
-0.61
-0.70
-0.80
0.28
MDB
-0.15
-0.19
-0.22
-0.28
0.13
MDC
-0.38
-0.37
-0.39
-0.43
0.06
*Data represent dimensional change over a range of sintering temperatures
CONCLUSIONS
When two new materials, Ancorloy MDB and Ancorloy MDC, were compared to a standard
FLN4-4405 material in the single press / single sinter production of a demanding automotive
part, the following items were noted:
• MDB was competitive with the FLN4-4405 material, despite a lower nickel content and a
lower sintered density,
• MDC exceeded the standard’s tensile strength and impact energy by over 30% and 50%,
respectively,
• Significant dimensional control benefits were realized when the Ancorloy materials were
substituted for the FLN4-4405 standard, and
• A potent sinter-hardening response was noted in MDC under standard cooling conditions.
FUTURE WORK
The next stage of this work, which has already begun, will compare the DP/DS properties of
each material. Additional data collection on fatigue performance, machining performance, and
reliability of MDB and MDC continue to be pursued in separate studies as well. As previously
stated, the underlying objective of these investigations will be to replace a fairly laborious
production process with a simpler three step process.
ACKNOWLEDGEMENTS
The authors wish to acknowledgment the support of HazenTec and Hoeganaes Corporation.
They would like to thank the staff of HazenTec and, in particular, Karen Hasley and Enola Altis
for their assistance in producing and processing the test specimens. The authors would also
like to thank George Fillari and Ronald Fitzpatrick of the Hoeganaes Corporation for their
contribution to mechanical testing and data collection.
REFERENCES
1. James, W.B, Causton, R.J., Baran, M.C., and Narasimhan, K.S., “New High Performance
P/M Alloy Substitutes for Malleable and Ductile Cast Irons,” Advances in Powder Metallurgy
& Particulate Materials, Metal Powder Industries Federation, Princeton, NJ, 2000.
2. Baran, M.C., Chawla, N., Murphy, T.F., and Narasimhan, K.S., “New High Performance
P/M Alloys for Replacing Ductile Cast Irons,” Advances in Powder Metallurgy & Particulate
Materials, Metal Powder Industries Federation, Princeton, NJ, 2000.
3. “Ductile Iron Data for Design Engineers,” Section 3, QIT-Fer et Titane Inc., 1990.
4. Salak, A., Ferrous Powder Metallurgy, Cambridge International Science Publishing,
Cambridge, England, 1995, p.235.
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