ANCORLOY HARDENABILITY
F. J. Semel
Hoeganaes Corporation, Cinnaminson, NJ 08077
ABSTRACT
The Continuous Sinter Cooling Transformation diagrams of five proprietary admix compositions
including Ancorloy 2® and Ancorloy 4® at sintered carbon contents of 0.50 w/o and Ancorloy
MDB®, Ancorloy MDC® and Ancorloy MDCL® at sintered carbon contents of 0.60 w/o are
3
presented for sintered densities in the neighborhood of 7.10 g/cm .
INTRODUCTION
The Ancorloys comprise a series of binder-treated premixes which develop excellent assintered mechanical properties in the normally cooled condition, (i.e. without benefit of the rapid
cooling typical of sinter hardening). Ancorloy 2 and Ancorloy 4 are the compositional
equivalents of the well known diffusion alloyed grades, FD-02 and FD-04, in accordance with
MPIF Standard 35. Ancorloy MDB, Ancorloy MDC, and Ancorloy MDCL are recently developed
alloys that are based on Ancorsteel 85HP®, an iron based pre-alloy having a nominal
molybdenum content of 0.85 w/o, and otherwise variously containing similar or larger admix
additions of either silicon or silicon and nickel, (1). Hence, all of these compositions are fairly
highly alloyed and consequently, have potential for sinter hardening applications. The object of
the present study was to quantify this potential in terms of Continuous Sinter Cooling
Transformation, (CSCT), diagrams as earlier developed to characterize the sinter hardenability
of Ancorsteel 737 SH®, (2).
EXPERIMENTAL PROCEDURE
The CSCT method is basically a special case of the more general Continuous Cooling
Transformation or CCT method of determining hardenability, (3). In both methods, high
temperature dilatometry is used to determine the temperatures of the phase transitions that
occur on cooling a series of specimens at different rates from a common austenitizing
temperature. Metallography and/or hardness determinations are then used to relate the cooling
rate and phase transition - temperature data diagrammatically to the microstructures and/or
relative hardness values that characterize the resulting specimens. The CSCT method,
however, is generally less comprehensive than the CCT method in that the determinations are
limited to the cooling rates that are typical of the average sinter hardening process. This
particular difference leads to the possibility of eliminating the logarithmic time scale that is used
in the CCT diagram and thus, of representing the findings in a somewhat different way in a socalled CSCT diagram.
Dilatometry Procedure
The dilatometer that was used in this study was, except for a minor change as explained below,
the same instrument as used in the earlier referenced study, (2). The dilatometric procedure
used was likewise similar but again, as will be explained, not precisely the same.
As originally designed, the dilatometer accommodates specimens with widths and heights in the
neighborhood of 1 cm and lengths of from 5 to 6 cm as typical of a standard PM impact bar. A
thermocouple well is normally drilled to a depth of about 0.65 cm into the end of the specimen
that interfaces with the probe rod which transmits the dilation to the micrometer measuring
head in the instrument. In thermal expansion and sintering studies, a long specimen length is
an advantage because dilations are correspondingly larger and easier to detect. However, in
continuous cooling studies, accurate determination of transition points requires the use of a
relatively short specimen to minimize the magnitude of the temperature variations from the point
of temperature measurement, (i.e. from the bottom of the TC well). The earlier study mentioned
had shown that this length should be no greater than about twice the depth of the TC well, or
about 1.25 cm. Specimens of this length could easily be cut from a pressed and sintered impact
bar. The difficulty, however, was to meet the requirement in the dilatometer. Two possibilities
existed to do this. One was to use a non-standard, (i.e. longer), probe rod to accommodate the
shorter length. The other was to supplement the standard length probe rod with an inert spacer
to make up the length difference. In the earlier study, the inert spacer was used. In the present
study, the dilatometer was equipped with a non-standard probe. As it turned out, this change
greatly simplified the analysis of the data and ostensibly increased the precision of the
measurements as well.
As to the procedure itself, the ideal situation with regard to using continuous cooling dilatometry
to characterize hardenability for sinter hardening applications would be to employ a procedure
that reasonably simulates the sinter hardening process. Unfortunately, however, there are
various practical impediments to doing this. One is that continuous cooling dilatometry requires
the use of quartz refractories which have a limited temperature range of applicability. In
o
particular, they are typically not recommended for use at temperatures much above 1000 C,
o
(1832 F), which, of course, is generally too low, at least for sintering, if not for hardening. Thus,
whereas in sinter hardening, the work is sintered and hardened in the same step, in continuous
cooling dilatometry, its ostensibly not only necessary to sinter and harden in separate steps but
to design the hardening step around a substantially lower austenitizing temperature than is
o
o
typical of the average sintering process, (e.g. 1120 C or 2050 F). In the earlier study, the
o
o
austenitizing temperature that was used was 950 C, (1740 F).
Since its well known in the heat treatment of steel that the austenitizing temperature may effect
the hardening response of the work, this low temperature limitation was considered to be an
essential weakness of the CSCT method. Consequently, consideration in advance of this study
was given to what possibilities existed to mitigate it. Based on a review of how the refractory
elements are stressed in the dilatometer and of the high temperature creep resistance of
quartz, it was decided that it was reasonable to risk, at least, short time exposure to
o
temperatures as high as 1120 C. Thus, the procedure that was used in heating for hardening
o
in the study was as follows. Initially, the specimens were heated at a rate of 10 C/min., (0.3
o
o
o
o
F/sec.), to 695 C, (1285 F), equalized for 10 minutes at temperature and heated at 5 C/min.
o
o
to 720 C, (1330 F). This pause was just in advance of the α to γ transformation and both it and
the subsequent change in heating rate was inserted to permit accurate determination of the
transformation start temperature which is generally useful information to have in addition to the
transformation behavior during cooling. After the pause, the specimens were again heated at a
o
o
rate of 10 C/min., and now to 1120 C, equalized for 10 minutes at temperature, slow cooled at
o
o
o
20 C/min. to 865 C, (1590 F), held for 5 minutes and thereafter submitted to accelerated
cooling for hardening. A programmable controller was used to implement the procedure. The
dilatometer atmosphere that was used during both the heating and cooling phases of the
process was 10% H2 and 90% He by volume, (hereafter, v/o), at a flow rate of 1.4 liters/min.,
(3 cfh).
As in the earlier Ancorsteel 737 SH study, cooling subsequent to austenitizing was principally
by black body radiation. By varying the specimen width and adjusting the re-radiant conditions,
o
it was possible to effect cooling rates, as averaged over the range from 850 to 315 C, (1560 to
o
o
o
o
600 F), that were as a high as 150 C/min., (4.5 F/sec.), or as low as 20 C/ min., (0.6
o
F/sec.). Typically, six cooling rates within this range were used to conduct a single study.
Specimen Preparation and Testing Subsequent to Hardening
Each of the subject compositions was prepared as a binder-treated premix and compacted into
3
standard impact specimens, (ASTM-23), having a nominal green density of 7.05 g/cm . The
graphite contents of the Ancorloy 2 and Ancorloy 4 mixes was adjusted to produce a sintered
o
o
carbon of 0.5 w/o. Sintering in these cases was at 1120 C, (2050 F), for 30 minutes at
temperature in synthetic DA, (i.e. 75 v/o H2 plus 25 v/o N2). The graphite contents of the
Ancorloy MDB, Ancorloy MDC and Ancorloy MDCL mixes was adjusted to produce a sintered
carbon of 0.6 w/o. Each of the these compositions contains a proprietary silicon additive that
requires high temperature sintering to develop optimum properties. Consequently, sintering in
o
o
these cases was at 1230 C, (2250 F), for 30 minutes at temperature in synthetic DA.
The dilatometry specimens in each case were cut from the sintered impact bars. They
measured 1.25 cm in length, 1.1 cm in height and, depending on the aim cooling rate, either
0.35, 0.75 or 1.0 cm in width.
Subsequent to hardening, the dilatometry specimens were first checked for density and then
sectioned transverse to their longitudinal axes about 2 mm below the bottom of the TC well.
The face of the piece containing the TC well was submitted to apparent hardness testing and
the piece was subsequently sectioned a second time parallel to this face to provide material to
check the sintered carbon content. The face of the opposing section, (i.e. the face opposite the
TC well), was mounted and polished for metallographic examination. The volume fractions of
martensite, bainite, pearlite and ferrite were quantitatively determined as separate from the
pore fraction by the point counting method. In most cases, the etchant was 4 w/o picral in
reagent alcohol, (i.e. 90 v/o ethanol).
RESULTS AND DISCUSSION
The sintered chemistries of the five alloys as determined from the remnants of the impact
specimens that were used to make the dilatometry specimens were as shown below in Table 1.
Ancorloy
ID
2
4
MDB
MDC
MDCL
Table 1 - Sintered Chemistries of the Subject Compositions
C
Mn
Si
Ni
Cu
w/o
w/o
w/o
w/o
w/o
0.51
0.18
0.02
1.72
1.45
0.50
0.17
0.02
3.84
1.43
0.63
0.13
0.68
2.23
0.05
0.62
0.12
0.65
4.50
0.04
0.61
0.12
0.38
4.60
0.04
Mo
w/o
0.51
0.50
0.79
0.76
0.77
A review of the these findings will show that the sintered carbon aims of 0.50 w/o in the
Ancorloy 2 and Ancorloy 4 compositions and of 0.60 w/o in the remaining alloys were both
reasonably attained. As it turned out, the sintered carbon checks of the dilatometry specimens
generally confirmed these findings but also indicated that the hardening process had resulted in
slight losses in every case of about 0.01 or 0.02 w/o.
The remaining alloy contents of the Ancorloy 2 and Ancorloy 4 compositions are probably
generally well known to those familiar with P/M as these alloys are the binder treated analogs of
the well known diffusion alloyed grades FD-02 and FD-04. However, this is almost certainly not
the case with the other alloys which are all recent additions to the art. Notice, first of all, that
whereas all of these alloys are made as premixes on an Ancorsteel 85 HP base which has a
nominal prealloyed molybdenum content of 0.85 w/o, none has a final molybdenum content in
excess of 0.80 w/o. In every case, this is a dilution effect of the other alloy additions that are
made to these premixes. In Ancorloy MDB, the other additions have nominal aims of 0.70 w/o
silicon and 2.00 w/o nickel. In Ancorloy MDC, the aims are 0.70 w/o silicon and 4.40 w/o nickel
and, in Ancorloy MDCL, they are 0.35 w/o silicon and 4.40 w/o nickel.
Finally, it may be of interest to note that the manganese values shown in the table essentially
represent the residual contents of the base powder. They were listed because, although small,
its known for a fact that they very definitely effect hardenability.
The hardenability findings of the study follow. As will be seen, the averaged results of the
sintered density checks that were done on the hardened specimens are listed in the titles of the
associated CSCT diagrams. As a general matter, these findings showed that the density either
3
stayed the same or increased relative to the original green value, (i.e. 7.05 g/cm ). As might be
expected, the observed increases correlated both with the nickel contents of the alloys and the
higher sintering temperature that was used with the newer ones.
Ancorloy 2 Hardenability @ 0.5% C, 1.5% Cu, 1.75% Ni & 0.50% Mo
The CSCT diagram of the Ancorloy 2 composition is shown overleaf in Figure 1. Notice that the
sintered and hardened density that was observed in this case was the same as the original
green density.
Otherwise, prior to discussing the findings in this figure, it may be useful to review the essential
elements of the basic diagram. There are four as follows:
1. The diagram is based a linear time scale rather than a logarithmic one as is commonly
the case in the standard CCT diagram.
2. The traces of three of the cooling profiles used in hardening the specimens along with
the associated average cooling rates are indicated in the diagram. These provide a
graphical matrix to indicate the transformation data.
3. The metallographic and apparent hardness results corresponding to the specimens that
comprised the study are presented in the form of a text box insert to the diagram.
4. The phase fields indicated by the dilatometric data are labeled in accordance with the
indications of the metallographic results. The legend which is used is as follows:
A - austenite, B - bainite, Fp - proeutectoid ferrite, M - martensite, and P - pearlite.
3
Ancorloy 2 - 0.5 w/o Sintered C at 7.05 g/cm
Continuous Sinter Cooling Transformation Diagram
1000
Microstructure & Apparent Hardness
Cooling Rate
M
B
P
F Hardness
900
o
C/min
131
115
107
77
52
30
800
A
o
Temperature C
700
600
500
%
24
26
29
24
16
10
%
5
5
3
1
1
--
%
71
69
68
75
83
90
%
-------
R/A
60
54
54
52
50
48
400
A+P+B
300
200
o
30 C/Min
o
131 C/Min
o
77 C/Min
M+P+B
100
M+P
0
0.0
5.0
10.0
15.0
20.0
25.0
Time (minutes)
Figure 1 - CSCT Diagram of Ancorloy 2 @ 0.5 w/o sintered carbon.
A review of this diagram will show that the hardening behavior of the Ancorloy 2 was
characterized by two transformations. One which did not appear to be very dependent on
o
o
cooling rate, started at ~560 C, (1040 F), and formed pearlite and bainite. The other formed
o
o
martensite and, at the highest cooling rate, started at ~300 C, (570 F). Subsequently, the start
temperature in this case decreased rather quickly with decrease in the cooling rate to a more or
o
o
less constant value of 260 C, (500 F). According to the Metallographic and Apparent
Hardness results, the pearlite transformation dominated the behavior. Martensite formed even
at the lowest cooling rate but in no case did its volume fraction exceed 30%. The apparent
hardness decreased uniformly with cooling rate from 60 RA, (20 RC), at the highest rate to 48
RA, (77 RB) at the lowest rate.
Interestingly, the two tier transformation behavior shown by this alloy tended to typify the
behaviors of each of the other alloys of the study. However, as will be seen, both the
temperature details of the transformations and the effects on microstructure and apparent
hardness were generally very different from alloy to alloy.
Ancorloy 4 Hardenability @ 0.5% C, 1.5% Cu, 4.00% Ni & 0.50% Mo
The CSCT diagram of the Ancorloy 4 composition is shown below in Figure 2. Note that the
3
3
sintered and hardened density that was observed in this case was 7.10 g/cm , 0.05 g/cm
higher than the original green density.
3
Ancorloy 4 - 0.5 w/o Sintered C at 7.10 g/cm
Continuous Sinter Cooling Transformation Diagram
1000
Microstructure & Apparent Hardness
Cooling Rate
M
B
P
F Hardness
900
o
C/min
134
117
110
79
49
28
800
o
Temperature C
700
A
600
500
%
56
52
52
43
32
32
%
7
3
3
2
2
1
%
37
45
45
55
66
67
%
-------
R/A
73
68
69
70
69
66
400
A+P+B
300
o
28 C/Min
200
o
134 C/Min
100
o
M+P+B
79 C/Min
M+P+B
0
0.0
5.0
10.0
15.0
20.0
25.0
Time (minutes)
Figure 2 - CSCT Diagram of Ancorloy 4 @ 0.5 w/o sintered carbon.
Based on a review of the data in this diagram, its evident that the additional nickel in the
Ancorloy 4 shifted the knee of the pearlite-bainite transformation significantly to the right as
compared to the Ancorloy 2. Although this is not apparent in the phase transition data, it is
easily deduced from the Metallographic and Apparent Hardness results. For example,
according to the phase transition data, there was little change in the transformation behavior
relative to that of the Ancorloy 2. The start temperature was only marginally lower, averaging
o
o
~550 C, (1020 F), and, like the Ancorloy 2, was otherwise relatively insensitive to the cooling
rate. However, the Metallographic and Apparent Hardness results clearly show that the
transformation was associated with less pearlite-bainite formation and thus, led to a significant
increase in the martensite content and in the apparent hardness values. Accordingly, these
data show that martensite is the dominant phase at the highest cooling rates and maintains a
significant presence even at the lower cooling rates. Similarly, the apparent hardness varies
from a high of 73 RA, (45 RC), to a low of 66 RA, (32 RC); the latter value being substantially
higher than the highest value of the Ancorloy 2.
In comparison, the effects of the nickel on the martensite transformation were more obvious. In
particular, its easily seen from a cursory review of the two diagrams that this transformation
occurred at lower temperatures in the Ancorloy 4 than in the Ancorloy 2. The martensite start
o
o
temperature at the highest cooling rate, in the Ancorloy 4, was ~260 C, (500 F), as compared
o
to the earlier value of 300 C. Thereafter, the start temperature decreased with decreasing
o
cooling rate, leveling off somewhat more gradually than earlier to a constant value of ~210 C,
o
o
o
(410 F). This was ~50 C, (90 F), lower than the low value of the Ancorloy 2 at the lowest
cooling rates.
Ancorloy MDB Hardenability @ 0.6% C, 0.7% Si, 2.00% Ni & 0.80% Mo
The CSCT diagram of the Ancorloy MDB composition is shown in Figure 3. The sintered and
hardened density indicated in the figure was again increased relative to the original green
density. However, the increase in this case was probably due to the high sintering temperature
that was employed rather to an effect of composition as in the case of the Ancorloy 4.
3
Ancorloy MDB - 0.6 w/o Sintered C at 7.1 g/cm
Continuous Sinter Cooling Transformation Diagram
900
Microstructure & Apparent Hardness
Cooling Rate
M
B
P
F Hardness
800
o
C/min
137
119
109
78
50
30
o
Temperature C
700
A
600
500
%
84
76
73
49
32
24
%
5
9
13
16
19
10
%
11
15
13
35
49
66
%
-------
R/A
74
73
72
69
67
63
400
A + B + P
300
o
30 C/min
o
78 C/min
200
o
137 C/min
M + B + P
100
0.0
5.0
10.0
15.0
20.0
25.0
Time (minutes)
Figure 3 - CSCT Diagram of Ancorloy MDB @ 0.6w/o sintered carbon.
Interestingly, a comparison of the these findings with those of the Ancorloy 4 gives an indication
of the greater effectiveness of carbon, silicon and molybdenum than copper and nickel in
increasing hardenability. For example, the Ancorloy 4 is about 2 w/o higher in total alloy content
than the Ancorloy MDB and virtually all of this difference is in its copper and nickel contents.
However, its evident by inspection of their respective CSCT diagrams that the Ancorloy MDB is
the more hardenable of the two. As with both of the earlier alloys, the Ancorloy MDB behavior is
characterized by two transformations. But both are at substantially lower temperatures than was
the case with the Ancorloy 4 and both led to generally higher martensite contents and higher
apparent hardness values, especially at the higher cooling rates. For example, at the highest
o
o
cooling rate, the pearlite-bainite start temperature of the Ancorloy MDB was ~500 C, (930 F),
o
as compared with 550 C for the Ancorloy 4. With decrease in the cooling rate, the start of the
o
transformation tended to increase gradually to higher temperatures but leveled off at ~515 C,
o
o
o
(960 F), about 35 C, (65 F), lower than the corresponding values of the Ancorloy 4. These
effects are thought to be due mainly to the silicon and to the higher molybdenum content of the
Ancorloy MDB. Both are known to be more effective in inhibiting the nucleation of the pearlitebainite reaction than copper and nickel, (4).
In the case of the martensite transformation, the start temperature at the highest cooling rate
o
o
was ~220 C, (430 F), and decreased almost linearly with decrease in the cooling rate to a low
o
o
o
o
of ~195 C, (385 F). As averaged over the entire range, this was about 20 C, (35 F), lower
than the average martensite start temperature of the Ancorloy 4. This difference is thought to
be largely attributable to the higher sintered carbon content of the Ancorloy MDB. The usual
explanation is that the carbon adds to the internal strain state of the austenite and inhibits the
transformation to martensite by increasing the shear stress needed to effect it, (5).
Finally, as shown by the Metallographic and Apparent Hardness results, the martensite volume
fraction of the Ancorloy MDB varied with cooling rate from a high of 84% to a low of 24%
exhibiting substantially higher contents than the Ancorloy 4 at the higher cooling rates but the
same and a somewhat lower content at the two lowest rates. An essentially similar relation
existed between the hardness variations of the two alloys. The apparent hardness of the
Ancorloy MDB varied from a high of 74 RA, (47 RC), to a low of 63 RA, (25 RC).
Ancorloy MDC Hardenability @ 0.6% C, 0.7% Si, 4.40% Ni & 0.80% Mo
The CSCT diagram of the Ancorloy MDC composition is shown in Figure 4. Notice that the
sintered and hardened density that is indicated in the figure was increased with respect to the
original green density as well to the sintered density of the Ancorloy MDB. Presumably, this
increase was due both to the high sintering temperature that was employed as well to an effect
of the higher nickel content of the Ancorloy MDC.
Interestingly, the effect of the higher nickel content on the hardenability of the Ancorloy MDC
compared with that of the Ancorloy MDB was very similar to the effect that it had on Ancorloy 4
versus Ancorloy 2. Essentially, the nickel shifted the knee of the pearlite-bainite transformation
significantly to the right. This was evidenced primarily by the metallographic results which
showed across the board increases in martensite and corresponding decreases in the pearlite
and bainite contents of the Ancorloy MDC versus the Ancorloy MDB. However, the effect was
also clear from the shape of the pearlite-bainite transformation curve itself which, as reference
to the figure will show, fell just short of actually defining a knee. In contrast, the nickel appeared
to have very little effect on the martensite transformation. The start temperatures were about
o
o
the same as they were in the Ancorloy MDB, averaging ~205 C, (400 F), over the entire range
of cooling rates. As might be expected, the apparent hardnesses of the Ancorloy MDC tracked
with the martensite contents and were generally increased relative to those of the Ancorloy
MDB. They ranged from a high of 75 RA, (49 RC), to a low value of 64 RA, (28 RC).
Figure 4 - CSCT Diagram of Ancorloy MDC @ 0.6w/o sintered carbon.
3
Ancorloy MDC - 0.6 w/o Sintered C at 7.15 g/cm
Continuous Sinter Cooling Transformation Diagram
900
Microstructure & Apparent Hardness
Cooling Rate
M
B
P
F Hardness
800
o
C/min
137
119
113
78
50
30
o
Temperature C
700
600
A
500
%
97
93
93
78
73
59
%
3
7
7
20
23
16
%
--T
2
4
25
%
-------
R/A
75
75
72
71
69
64
400
300
A+B
A + P + B
o
30 C/min
200
o
137 C/min
M + B
o
78 C/min
M + B + P
100
0.0
5.0
10.0
15.0
20.0
25.0
Time (minutes)
Ancorloy MDCL Hardenability @ 0.6% C, 0.35% Si, 4.40% Ni & 0.80% Mo
The CSCT diagram of the Ancorloy MDCL composition is shown overleaf in Figure 5.
Reference to the figure in this case will show that there was no effect of the decrease in silicon
content on the sintered and hardened density relative to that of the Ancorloy MDC.
The decrease in the silicon content had an interesting and complex effect on hardenability.
Comparison of the Metallographic and Apparent Hardness findings will show general decreases
in the martensite contents and apparent hardness values of the Ancorloy MDCL versus the
Ancorloy MDC with decreasing cooling rate. However, instead of otherwise precipitating pearlite
as was primarily the case with most of the other alloys of the study, the Ancorloy MDCL
precipitated increased amounts of bainite. Although this was also evident in the behavior of the
Ancorloy MDC, it was not nearly as clearly indicated as it was here. As reference to the CSCT
diagram in Figure 5 will confirm, the trade off between pearlite and bainite was most evident
through the mid-range and lower cooling rates where its effect was also manifest as a reversal
of the usual trend of decreasing apparent hardness with decreasing cooling rate. In particular,
the apparent hardness values of the Ancorloy MDCL first decrease then increase and then
decrease again with decreasing cooling rate. Interestingly, at the very lowest cooling rates, the
hardness values of the Ancorloy MDCL were actually either equal to or greater than those of
the Ancorloy MDC.
The microstructural effects of the decrease in silicon can also be rationalized in terms of the
pearlite-bainite transformation start temperatures that were observed. In the Ancorloy MDC, the
o
o
start temperatures ranged with decreasing cooling rate from a low of 455 C, (850 F), to a high
o
o
o
o
of 530 C, (985 F), precipitating mostly bainite at temperatures below ~510 C, (950 F), and
mostly pearlite at the higher ones. In the case of the Ancorloy MDCL, the pearlite-bainite start
o
o
o
temperatures were uniformly below 510 C ranging from 480 to 500 C, (895 to 930 F), and
consequently, precipitated mostly bainite.
3
Ancorloy MDCL - 0.6 w/o Sintered C at 7.15 g/cm
Continuous Sinter Cooling Transformation Diagram
1000
Microstructure & Apparent Hardness
Cooling Rate
M
B
P
F Hardness
900
o
C/min
137
123
113
78
50
30
800
o
Temperature C
700
600
A
500
%
97
89
81
64
54
51
%
3
11
19
36
42
38
%
-T
T
1
4
11
%
-------
R/A
73
68
69
70
69
66
400
300
A+B
A+P+B
o
30 C/Min
200
o
M+B
137 C/Min
100
o
78 C/Min
M+B+P
0
0.0
5.0
10.0
15.0
20.0
25.0
Time (minutes)
Figure 5 - CSCT Diagram of Ancorloy MDCL @ 0.6w/o sintered carbon.
The martensite start temperatures of the Ancorloy MDCL were also unexpectedly affected by
the decrease in silicon in that they were generally lower than they were in the case of the
o
o
o
Ancorloy MDC. They averaged 195 C, (385 F), about 10 C lower than that of the latter alloy,
o
o
ranging from 220 to 180 C, (430 to 355 F). For the record, the apparent hardness values of
the Ancorloy MDCL ranged from a high of 73 RA, (45 RC), to a low of 66 RA, (32 RC).
SUMMARY AND CONCLUSIONS
The continuous cooling transformation characteristics of five alloys including Ancorloy 2,
Ancorloy 4, Ancorloy MDB, Ancorloy MDC, and Ancorloy MDCL were determined for six cooling
o
o
rates in the range from 150 to 20 C/min., (4.5 to 0.6 F/sec.). Owing to equipment limitations, it
was necessary to sinter and harden in separate steps. The Ancorloy 2 and Ancorloy 4 alloys
o
o
were sintered at 1120 C, (2050 F). The remaining three alloys all contained silicon which
o
necessitated high temperature sintering. As a consequent, they were each sintered at 1235 C,
o
(2250 F). To ensure complete dissolution of alloy precipitates as well as to mitigate concerns
o
for the possible effects of grain size on hardenability, austenitizing for hardening was at 1120 C
in all cases. The findings were presented in the form of CSCT diagrams which in addition to the
resultant phase transition data contained a summary of the quantitative metallographic and
apparent hardness results at each cooling rate. As a general matter, the findings showed that
hardenability increased with increasing alloy content.
Ancorloy 2 which had the lowest base alloy content, (i.e. 1.5 w/o Cu, 1.75 w/o Ni and 0.5 w/o
3
Mo), exhibited the lowest hardenability. At a density of 7.05 g/cm and a sintered carbon
content of 0.5 w/o, its microstructure was predominantly pearlitic at all cooling rates. At mido
o
range cooling rates in the neighborhood of 100 C/min., (3 F/sec.), it exhibited a martensite
content of about 25 v/o and an apparent hardness value of 52 RA, (85 RB).
Ancorloy 4 which adds 2.25 w/o nickel to the base alloy content of Ancorloy 2, had the next
3
highest hardenability. At a density of 7.10 g/cm and a sintered carbon content of 0.5 w/o, it
exhibited a mostly martensitic microstructure at the highest cooling rates but was again
predominantly pearlitic at the lower cooling rates. At mid-range cooling rates, its martensite
content was slightly upwards of 50 v/o and its apparent hardness was ~70 RA, (39 RC).
Ancorloy MDB with a base alloy content which may be viewed as substituting silicon and extra
nickel and molybdenum for the copper of Ancorloy 2, (i.e. specifically, 0.7 w/o Si, 2.0 w/o Ni and
3
0.8 w/o Mo), had the next highest hardenability. At a density of 7.10 g/cm and a sintered
carbon content of 0.6 w/o, it exhibited martensite contents that when compared with those of
the Ancorloy 4 were substantially higher at the highest cooling rates and roughly similar at the
o
lower cooling rates. At mid-range cooling rates, (i.e. ~100 C/min.), its martensite content was
about 70 v/o and its apparent hardness was ~71 RA, (41 RC).
Ancorloy MDC which adds 2.4 w/o nickel to the base alloy content of the Ancorloy MDB, had
3
the highest alloy content and the highest hardenability. At a density of 7.15 g/cm and a
sintered carbon content of 0.6 w/o, it exhibited a predominantly martensitic microstructure at all
o
cooling rates. At mid-range cooling rates, (again ~100 C/min.), its martensite content was
about 85 v/o and its apparent hardness was ~72 RA, (43 RC).
Ancorloy MDCL which reduces the silicon content of the Ancorloy MDC by 0.35 w/o, had the
fourth highest alloy content in the series and the fourth highest hardenability. At a density of
3
7.15 g/cm and a sintered carbon content of 0.6 w/o, it too, like the Ancorloy MDC, exhibited a
predominantly martensitic microstructure at all cooling rates. At mid-range cooling rates, its
martensite content was about 75 v/o and its apparent hardness was ~70 RA, (39 RC).
ACKNOWLEDGEMENTS
The author wishes to acknowledge the help of Messrs. W. B. Bentcliff, G. Golin and T. Murphy
of the Hoeganaes Laboratory in obtaining the data used in preparing the present manuscript.
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