BACKGROUND OF THE INVENTION
Field of the Invention
[0001] The present invention relates to a nitrogen-containing sintered hard alloy, and more
particularly, it relates to a nitrogen-containing sintered hard alloy which is improved
in thermal shock resistance, wear resistance and strength for serving as a material
for a cutting tool and enabling application to wet cutting.
Description of the Background Art
[0002] A nitrogen-containing sintered hard alloy having a hard phase of a carbo-nitride
mainly composed of Ti, which is bonded by a metal containing Ni and Co, has already
been put into practice as a cutting tool. This nitrogen-containing sintered hard alloy
is widely applied to a cutting tool similarly to the so-called cemented carbide which
is mainly composed of WC, since the hard phase is extremely fined as compared with
a conventional sintered hard alloy which is free from nitrogen to remarkably improve
high-temperature creep resistance as the result.
[0003] In this nitrogen-containing sintered hard alloy, however, resistance against a thermal
shock is reduced for the following reasons:
(i) The thermal conductivity of this nitrogen-containing sintered hard alloy is about
half that of the cemented carbide since the thermal conductivity of Ti which is the
main component of the carbo-nitride is extremely smaller than that of WC which is
the main component of the cemented carbide, and
(ii) the thermal expansion coefficient of the nitrogen-containing sintered hard alloy
is about 1.3 times that of the cemented carbide, since this coefficient also depends
on the characteristic value of the main component similarly to the thermal conductivity.
Therefore, the nitrogen-containing sintered hard alloy is disadvantageously inferior
in reliability to a coated cemented carbide or the like in cutting under conditions
bringing a particularly strong thermal shock such as milling, cutting of a square
timber with a lathe or wet copying with remarkable variation in depth of cut, for
example.
[0004] In order to solve such problems of the conventional nitrogen-containing sintered
hard alloy, various improvements have been attempted as follows: For example, Japanese
Patent Laying-Open No. 2-15139 (1990) proposes means of improving surface roughness
of a material containing at least 50 percent by weight of Ti in terms of a carbide
or the like and less than 40 percent by weight of an element belonging to the group
6A (the group VIB in the CAS version) in terms of a carbide and having an atomic ratio
N/(C + N) of 0.4 to 0.6 with a high nitrogen content by controlling the sintering
atmosphere, for forming a modified part having high toughness and hardness in a surface
layer part. On the other hand, Japanese Patent Laying-Open No. 5-9646 (1993) discloses
a cermet which is prepared by sintering a material, which is mainly composed of Ti,
containing less than 40 percent by weight of W, Mo and Cr in total in terms of a carbide,
and thereafter controlling a cooling step for providing a surface part with a region
having a smaller amount of binder phase as compared with the interior, to leave compressive
stress on the surface.
[0005] However, each of the cermets disclosed in the aforementioned gazettes is insufficient
in chipping resistance as compared with the coated cemented carbide, although wear
resistance and toughness are improved. Further, the cermet is so inferior in thermal
shock resistance that sudden chipping is easily.caused by occurrence of thermal cracking
or crack extension resulting from both thermal and mechanical shocks in particular,
and sufficient reliability cannot be attained. Although the manufacturing cost for
such prior art is reduced due to omission of a coating step, the performance cannot
be sufficiently improved. This suggests that improvement in strength against chipping
is naturally limited in the category of the so-called cermet which is prepared on
the premise that the same contains Ti in excess of a certain degree of amount.
[0006] The inventors have made deep study on analysis of cutting phenomenons such as temperature
distributions in various cutting operations and arrangements of material components
in tools, to obtain the following recognition:
[0007] During cutting, a cutting portion is partially exposed to high-temperature environment
in a surface part of an insert which is in contact with a workpiece, a part of a rake
face which is fretted by chips, and the like. Comparing the cermet with the cemented
carbide, the thermal conductivity of the former is about half that of the latter as
hereinabove described, and hence heat which is generated on the surface of the cermet
is so hardly diffused into the interior that the temperature is abruptly reduced in
the interior although the surface is at a high temperature. Once cracking is caused
in such a state, the cermet is extremely easily chipped. When the cermet is rapidly
quenched with water-soluble cutting oil from a high temperature state or cooled with
cutting in lost motion, further, only an extremely small part of its surface is quenched.
[0008] Comparing the cermet with the cemented carbide, further, the thermal expansion coefficient
of the former is about 1.3 times that of the latter as hereinabove described, and
hence tensile stress is caused on a surface layer part to-extremely easily cause thermal
cracking. In relation to either characteristic, the cermet is inferior in thermal
shock resistance to the cemented carbide.
[0009] Comparing the cermet and the cemented carbide having the same grain sizes and the
same amounts of binder phases, further, the fracture toughness of the former is reduced
by about 30 to 50 % as compared with the latter, and hence crack extension resistance
is also reduced in the interior of the alloy.
[0010] In the conventional nitrogen-containing sintered hard alloy, as hereinabove described,
there are limits to improvement of thermal conductivity, reduction of the thermal
expansion coefficient and improvement of crack extension resistance with a large content
of Ti which can bring an excellent machined surface and is advantageous in view of
the resource.
SUMMARY OF THE INVENTION
[0011] An object of the present invention is to provide a nitrogen-containing sintered hard
alloy which can be employed as a cutting tool in high reliability with no surface
coating also in a working region under conditions bringing a strong thermal shock
with no requirement for the high-priced coated cemented carbide which has been employed
in general.
[0012] The problem is solved by the features of claim 1.
[0013] The nitrogen-containing sintered hard alloy according to the present invention is
provided in its interior with a larger amount of WC as compared with the conventional
nitrogen-containing sintered hard alloy in structure, to be improved in resistance
against crack extension. When a large amount of WC is blended, WC particles toward
the alloy surface appear in the conventional nitrogen-containing sintered hard alloy
to provide a tool material called a P-type material, while this tool material is inferior
in smoothness of the machined surface. Therefore, this material is also remarkably
inferior in abrasive wear resistance to the so-called cermet or coated cemented carbide.
[0014] However, it has been proved possible to eliminate WC particles from a soft layer
which is present in the outermost surface of the tool, i.e., a surface part up to
a specific depth from a portion immediately under the so-called exudation layer, deciding
smoothness of the machined surface. Thus, abrasive wear resistance and crater wear
resistance can be remarkably improved, while the amount of a binder phase is reduced
in the vicinity of the surface layer and a group 6A metal such as W is solidly solved
in hard phase particles at the same time when cooling is carried out in a decarburizing
atmosphere such as a vacuum. Further, the alloy surface is hardened and toughness
can be improved by such an effect that compressive stress against the surface part
is caused by difference in thermal expansion coefficient due to a gradient in the
amount of the binder phase, whereby wear resistance and thermal shock resistance can
be remarkably improved.
[0015] Thermal cracking is caused by temperature difference between the surface part and
the interior of the alloy. In order to prevent such thermal cracking, the thermal
conductivity of the nitrogen-containing sintered hard alloy itself may be improved,
while the improvement of the thermal conductivity of the nitrogen-containing sintered
hard alloy is naturally limited. As a result of study, however, it has been clarified
that heat which is generated during cutting is conducted to the overall alloy to attain
a heat divergence (fin) effect when a layer having high thermal conductivity which
is rich in WC with a rest of a metal binder phase mainly composed of Co and Ni is
arranged on a surface part of a nitrogen-containing sintered hard alloy.
[0016] Accordingly, a nitrogen-containing sintered hard alloy according to the present invention,
which has been proposed on the basis of the aforementioned result of the study, includes
a hard phase containing WC serving as an essential element and a carbide, a nitride
or a carbo-nitride of at least one transition metal selected from the groups 4A, 5A
and 6A of the periodic table or a composite carbo-nitride thereof, and a binder phase
containing Ni, Co and unavoidable impurities, and has the following structure and
composition:
[0017] An exudation layer 1 containing a metal binder phase, mainly composed of Ni and Co,
and WC is present on an alloy surface part (see Figs. 1 to 3), and this layer 1 is
internally divided into three layers including an outermost layer containing at least
0 percent by volume and not more than 30 percent by volume (preferably 0 to 5 percent
by volume) of WC with a rest formed by a metal binder phase which is mainly composed
of Co and Ni, an intermediate layer containing at least 50 percent by volume and not
more than 100 percent by volume (preferably 80 to 100 percent by volume) of WC with
a rest formed by a metal binder phase which is mainly composed of Co and Ni, and a
lowermost layer containing at least 0 percent by volume and not more than 30 percent
by volume (preferably 0 to 5 percent by volume) of WC with a rest formed by a metal
binder phase which is mainly composed of Co and Ni.
[0018] The outermost and lowermost layers are at least 0.1 µm and not more than 10 µm (preferably
0.1 to 0.5 µm) in thickness, while the intermediate layer is at least 0.5 µm and not
more than 10 µm (preferably 0.5 to 5 µm) in thickness.
[0019] In the nitrogen-containing sintered hard alloy having the aforementioned structure,
thermal shock resistance is remarkably improved. While the outermost and lowermost
layers are substantially rich in the metal binder phase mainly composed of Ni and
Co, these layers are inevitably formed in the manufacturing steps, and no problem
is caused in performance when the thicknesses thereof are in the aforementioned range.
[0020] In the numeric limitation of the aforementioned structure, the intermediate layer
contains at least 50 percent by volume and not more than 100 percent by volume of
WC since desired thermal conductivity cannot be attained and the layer cannot serve
as a thermal divergence layer if the WC content is not more than 50 percent by volume
with a rest of the metal binder phase mainly composed of Co and Ni. The thickness
of this intermediate layer is set in the range of at least 0.5 µm and not more than
10 µm since desired thermal conductivity cannot be attained if the thickness is less
than 0.5 µm while wear resistance is remarkably deteriorated if the thickness exceeds
10 µm.
[0021] Each of the outermost and lowermost layers, which are necessarily formed for obtaining
the most important intermediate layer, must have a thickness of 0.1 µm, while the
same may cause welding with a main component of a workpiece and iron in cutting leading
to chipping if the thickness exceeds 10 µm. It has been proved by a result of study
that no influence is exerted on cutting performance if the outermost and lowermost
layers are not more than 10 µm in thickness.
[0022] In a preferred embodiment, the inventive nitrogen-containing sintered hard alloy
of the aforementioned structure has a region containing absolutely no or not more
than 2 percent by volume of a metal binder phase in its surface part immediately under
the exudation layer 1 containing the metal binder phase, which is mainly composed
of Ni and Co, and WC, and this region has a thickness of at least 2 µm and not more
than 100 µm (preferably 2 to 50 µm) from the portion immediately under the exudation
layer 1 toward the interior. According to this structure, the region immediately under
the exudation layer 1 has extremely high hardness, whereby both of wear resistance
and thermal shock resistance can be compatibly attained.
[0023] In the aforementioned structure, the surface part of the alloy contains not more
than 2 percent by volume of the metal binder phase which is mainly composed of Co
and Ni since no remarkable improvement of wear resistance is recognized if the metal
binder phase is present in a higher ratio. The thickness of the region located immediately
under the exudation layer 1 is set in the range of at least 2 µm and not more than
100 µm since no improvement of wear resistance is recognized if the thickness of the
region is less than 2 µm while the region is rendered too hard and fragile to deteriorate
chipping resistance if the thickness exceeds 100 µm.
[0024] In a more preferred embodiment of the inventive nitrogen-containing sintered hard
alloy having the aforementioned structure, the region containing absolutely no or
not more than 2 percent by volume of WC located immediately under the exudation layer
1 has a thickness of at least 1 µm and not more than 500 µm (preferably 20 to 100
µm) toward the interior of the alloy. Under such conditions, further, the abundance
of WC is preferably gradually increased from the aforementioned region located immediately
under the exudation layer 1 toward the interior so that the volume percentage of WC
reaches the average WC volume percentage of the overall alloy at a depth within 1
mm (preferably 0.3 to 0.7 mm) from the portion immediately under the exudation layer
1. According to this structure, the Young's modulus of the overall alloy is increased
due to the presence of WC, whereby mechanical strength is remarkably improved. Further,
both of thermal shock resistance and chipping resistance can be compatibly attained
by providing WC only in the interior with no presence on the surface part of the alloy.
[0025] In the aforementioned structure, the thickness of the region, located immediately
under the exudation layer 1, containing absolutely no or not more than 2 percent by
volume of WC toward the internal direction is set in the range of at least 1 µm and
not more than 500 µm since wear resistance is deteriorated due to influence by reduction
in hardness caused by WC if the thickness is less than 1 µm while the effect of improving
toughness of the alloy itself by WC cannot be attained if the thickness exceeds 500
µm.
[0026] The aforementioned structure of the inventive alloy can be obtained by setting a
sintering temperature in the range of 1350 to 1700°C in a specified composition and
controlling a sintering atmosphere and a cooling rate. The thicknesses of the three
layers forming the exudation layer 1 can be adjusted by controlling the sintering
temperature and the cooling rate.
[0027] The volume percentage of WC is measured by the following method: A section of a WC-Co
cemented carbide member having a known WC content is lapped to take a SEM photograph
of 4800 magnifications. An area occupied by WC in this photograph is calculated by
an image analyzer, to draw a calibration curve on the area occupied by WC. As to the
inventive alloy, a section of a portion to be observed is lapped and an area occupied
by WC is calculated from an SEM photograph of 4800 magnifications by an image analyzer,
for obtaining the volume percentage of WC from a calibration curve.
[0028] The foregoing and other objects, features, aspects and advantages of the present
invention will become more apparent from the following detailed description of the
present invention when taken in conjunction with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0029]
Fig. 1 is a microphotograph (SEM photograph) of an alloy structure indicating an exudation
layer which is divided into three layers with presence of Co and Ni binder layers
in outermost and lowermost layers and a WC layer in an intermediate layer; and
Figs. 2 and 3 are microphotographs (EDX analysis) indicating distributions of Co and
Ni elements in the structure respectively.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0030] Concrete Examples of the present invention are now described.
Example 1
[0031] TiCN powder, WC powder, TaC powder, NbC powder, Mo
2C powder, VC powder, (Ti
0.5W
0.3Ta
0.1Nb
0.1)C
0.5N
0.5 powder, Co powder and Ni powder of 1.5 µm in mean particle size were blended into
a composition shown at A in Table 1, mixed with each other in a wet attriter for 12
hours, thereafter worked into green compacts of a CNMG432 shape under a pressure of
1.5 ton/cm
2, and the green compacts were honed to thereafter prepare sintered hard alloys having
structures shown in Tables 3 to 5 under sintering conditions shown in Table 2. Referring
to Tables 3 to 5, the columns "structure from portion immediately under exudation
layer toward interior" show composition rates of hard phases and binder phases varied
with depths toward interiors of alloys with reference to portions immediately under
exudation layers which are set at 0. In a sample a-7, for example, the WC content
is identical to the alloy-average WC volume percentage from the portion immediately
under the exudation layer toward the interior, while the binder phase content is 1.8
percent by volume up to 2.5 µm, gradually increased from 2.5 µm up to 60 µm, and identical
to the alloy-average binder phase volume percentage in an internal portion beyond
60 µm. The content of the hard phase forming the rest is expressed in 100 - (alloy-average
binder phase volume percentage) - (alloy-average WC volume percentage) in each depth.
Table 1
Blending Composition (wt.) |
|
|
Hard Phase Component |
Binder Phase Component |
A |
TiCN 46 % WC 40 % |
Co 7 % Ni 7 % |
B |
TiCn 41 % WC 30 % TaC 5 % NbC 5 % Mo2 C3 % VC 2 % |
Co 7 % Ni 7 % |
C |
(Ti0.5, W0.3, Ta0.1, Nb0.1) (C0.5, N0.5) 86 % |
Co 7 % Ni 7 % |
D |
TiCN 66 % WC 16 % |
Co 9 % Ni 9 % |
Table 2
Sintering No. |
Sintering Condition |
|
Sintering Temperature (°C) |
Sintering Atmosphere (Torr) |
Cooling Rate (°C/min) |
Cooling Atmosphere (Torr) |
1 |
1530 |
Nitrogen : 5 |
8 |
Nitrogen : 3 |
2 |
1520 |
Nitrogen : 50 |
2 |
Nitrogen : 4 |
3 |
1400 |
Nitrogen : 3 |
4 |
Nitrogen : 4 |
4 |
1460 |
Nitrogen : 6 |
2 |
Nitrogen : 5 |
5 |
1460 |
Nitrogen : 10 |
2 |
Nitrogen : 10 |
6 |
1420 |
Nitrogen : 5 |
1 |
Nitrogen : 12 |
7 |
1435 |
Nitrogen : 6 |
4 |
Vacuum |
8 |
1530 |
Nitrogen : 5 |
8 |
Vacuum |
9 |
1520 |
Nitrogen : 2 |
2 |
Methane : 2 |
10 |
1400 |
Nitrogen : 50 |
4 |
Methane : 1 |
11 |
1460 |
Nitrogen : 6 |
2 |
Methane : 2 |
12 |
1420 |
Nitrogen : 5 |
1 |
Argon : 2 |
13 |
1435 |
Nitrogen : 6 |
4 |
Argon : 5 |
14 |
1530 |
Nitrogen : 5 |
8 |
Vacuum |
15 |
1420 |
Nitrogen : 10 |
1 |
Vacuum |
[0032] The samples a-1 to a-15 were subjected to a thermal shock resistance test and a wear
resistance test under conditions (A) and (B) respectively. Table 6 shows the results.
(A)
Workpiece: SCM435 (HB: 250) with four flutes
Cutting Speed: 100 (m/min.)
Depth of Cut: 1.5 (mm)
Feed Rate: 0.20 (mm/rev.)
Cutting Time: 30 sec.
Wet Type
(B)
Workpiece: SCM435 (HB: 250) with four flutes
Cutting Speed: 180 (m/min.)
Depth of Cut: 1.5 (mm)
Feed Rate: 0.30 (mm/rev.)
Cutting Time: 20 min.
Wet Type
Table 6
|
Sample |
(A) |
(B) |
|
a-1 |
38 Inserts |
0.29 mm |
* |
a-2 |
16 Inserts |
0.19 mm |
|
a-3 |
36 Inserts |
0.30 mm |
|
a-4 |
37 Inserts |
0.31 mm |
|
a-5 |
38 Inserts |
0.29 mm |
* |
a-6 |
16 Inserts |
0.25 mm |
* |
a-7 |
10 Inserts |
0.10 mm |
* |
a-8 |
10 Inserts |
0.08 mm |
* |
a-9 |
11 Inserts |
0.18 mm |
* |
a-10 |
19 Inserts |
0.08 mm |
* |
a-11 |
10 Inserts |
0.19 mm |
* |
a-12 |
10 Inserts |
0.18 mm |
* |
a-13 |
12 Inserts |
0.23 mm |
* |
a-14 |
17 Inserts |
0.18 mm |
* |
a-15 |
5 Inserts |
0.07 mm |
*: inventive samples |
(A): number of chipped ones among 40 inserts |
(B): flank wear width |
[0033] It is understood that thermal shock resistance which is superior to that of the prior
art can be attained when a sintered hard alloy having a hard phase consisting of TiCN
and WC is provided with an exudation layer as specified. It is also understood that
wear resistance and thermal shock resistance are improved respectively when binder
phase and WC distributions as specified are provided.
Example 2
[0034] Raw powder materials which were identical to those of Example 1 were blended into
a composition shown at B in Table 1, worked into green compacts by a method identical
to that in Example 1, and the green compacts were honed to prepare sintered hard alloys
having structures shown in Tables 7 to 9 under the sintering conditions shown in Table
2. Samples b-1 to b-15 were subjected to a thermal shock resistance test and a wear
resistance test under conditions (C) and (D) respectively. Table 10 shows the results.
(C)
Workpiece: SCM435 (HB: 300) with four flutes
Cutting Speed: 120 (m/min.)
Depth of Cut: 1.5 (mm)
Feed Rate: 0.20 (mm/rev.)
Cutting Time: 30 sec.
Wet Type
(D)
Workpiece: SCM435 (HB: 300) with four flutes
Cutting Speed: 200 (m/min.)
Depth of Cut: 1.5 (mm)
Feed Rate: 0.30 (mm/rev.)
Cutting Time: 20 min.
Wet Type
Table 10
|
Sample |
(C) |
(D) |
|
b-1 |
39 Inserts |
0.31 mm |
* |
b-2 |
15 Inserts |
0.17 mm |
|
b-3 |
37 Inserts |
0.32 mm |
|
b-4 |
38 Inserts |
0.33 mm |
|
b-5 |
39 Inserts |
0.31 mm |
* |
b-6 |
15 Inserts |
0.23 mm |
* |
b-7 |
9 Inserts |
0.08 mm |
* |
b-8 |
9 Inserts |
0.06 mm |
* |
b-9 |
10 Inserts |
0.15 mm |
* |
b-10 |
18 Inserts |
0.05 mm |
* |
b-11 |
9 Inserts |
0.16 mm |
* |
b-12 |
9 Inserts |
0.15 mm |
* |
b-13 |
11 Inserts |
0.20 mm |
* |
b-14 |
16 Inserts |
0.15 mm |
* |
b-15 |
4 Inserts |
0.04 mm |
*: inventive samples |
(C): number of chipped ones among 40 inserts |
(D): flank wear width |
[0035] It is understood that thermal shock resistance which is superior to that of the prior
art can be attained when a sintered hard alloy having a hard phase consisting of an
element belonging to the group 4A, 5A or 6A is provided with an exudation layer as
specified. It is also understood that wear resistance and thermal shock resistance
are improved respectively when binder phase and WC distributions as specified are
provided.
Example 3
[0036] Raw powder materials which were identical to those of Example 1 were blended into
a composition shown at C in Table 1, worked into green compacts by a method identical
to that in Example 1, and the green compacts were honed to prepare sintered hard alloys
having structures shown in Tables 11 to 13 under the sintering conditions shown in
Table 2. Samples c-1 to c-15 were subjected to a thermal shock resistance test and
a wear resistance test under conditions (E) and (F) respectively. Table 14 shows the
results.
(E)
Workpiece: SCM435 (HB: 280) with four flutes
Cutting Speed: 120 (m/min.)
Depth of Cut: 1.5 (mm)
Feed Rate: 0.20 (mm/rev.)
Cutting Time: 30 sec.
Wet Type
(F)
Workpiece: SCM435 (HB: 280)
Cutting Speed: 200 (m/min.)
Depth of Cut: 1.5 (mm)
Feed Rate: 0.30 (mm/rev.)
Cutting Time: 20 min.
Wet Type
Table 14
|
Sample |
(E) |
(F) |
|
c-1 |
39 Inserts |
0.32 mm |
* |
c-2 |
16 Inserts |
0.16 mm |
|
c-3 |
37 Inserts |
0.33 mm |
|
c-4 |
38 Inserts |
0.34 mm |
|
c-5 |
39 Inserts |
0.32 mm |
* |
c-6 |
17 Inserts |
0.22 mm |
* |
c-7 |
10 Inserts |
0.07 mm |
* |
c-8 |
10 Inserts |
0.05 mm |
* |
c-9 |
11 Inserts |
0.14 mm |
* |
c-10 |
19 Inserts |
0.04 mm |
* |
c-11 |
10 Inserts |
0.15 mm |
* |
c-12 |
10 Inserts |
0.14 mm |
* |
c-13 |
12 Inserts |
0.19 mm |
* |
c-14 |
17 Inserts |
0.14 mm |
* |
c-15 |
Inserts |
0.03 mm |
*: inventive samples |
(E): number of chipped ones among 40 inserts |
(F): flank wear width |
[0037] It is understood that thermal shock resistance which is superior to that of the prior
art can be attained when a sintered hard alloy having a solid solution hard phase
consisting of an element belonging to the group 4A, 5A or 6A is provided with an exudation
layer as specified. It is also understood that wear resistance and thermal shock resistance
are improved respectively when binder phase and WC distributions as specified are
provided.
Example 4
[0038] The samples a-1 and a-2 shown in Table 3 and the sample a-1 shown in Table 13 were
subjected to a thermal shock resistance test under conditions (G). Table 15 shows
the results.
(G)
Workpiece: SCM435 (HB: 280) with four flutes
Cutting Speed: 100 (m/min.)
Depth of Cut: 1.5 (mm)
Feed Rate: 0.20 (mm/rev.)
Cutting Time: 30 sec.
Wet Type
Table 15
|
Sample |
(G) |
* |
a-1 |
15 Inserts |
|
a-2 |
32 Inserts |
|
a-3 |
36 Inserts |
*: inventive sample
(G): number of chipped ones among 40 inserts |
[0039] It is understood that no improvement of thermal shock resistance is recognized despite
an exudation layer, if no layer which is mainly composed of WC is present.
[0040] Although the present invention has been described and illustrated in detail, it is
clearly understood that the same is by way of illustration and example only.
1. A nitrogen-containing sintered hard alloy including a hard phase containing WC serving
as an essential element and a carbide, a nitride or a carbo-nitride of at least one
transition metal being selected from the groups 4A, 5A and 6A of the periodic table
or a composite carbo-nitride thereof, and a binder phase containing Ni, Co and unavoidable
impurities, an exudation layer containing a metal binder phase, mainly composed of
Ni and Co, and WC being present on an alloy surface part, said exudation layer being
internally divided into three layers in order of an outermost layer, an intermediate
layer and a lowermost layer, said outermost layer containing at least 0 percent by
volume and not more than 30 percent by volume of WC with a rest being formed by a
metal binder phase mainly composed of Co and Ni, said intermediate layer containing
at least 50 percent by volume and not more than 100 percent by volume of WC with a
rest being formed by a metal binder phase mainly composed of Co and Ni, said lowermost
layer containing at least 0 percent by volume and not more than 30 percent by volume
of WC with a rest being formed by a metal binder phase mainly composed of Co and Ni,
said outermost and lowermost layers being at least 0.1 µm and not more than 10 µm
in thickness, said intermediate layer being at least 0.5 µm and not more than 10 µm
in thickness.
2. The nitrogen-containing sintered hard alloy in accordance with claim 1, being provided
with a region containing absolutely no or not more than 2 percent by volume of said
metal binder phase mainly composed of Co and Ni in a portion immediately under said
exudation layer, said region having a thickness of at least 2 µm and not more than
100 µm from said portion immediately under said exudation layer toward the interior.
3. The nitrogen-containing sintered hard alloy in accordance with claim 1, being provided
with a region containing absolutely no or not more than 2 percent by volume of WC
in a portion immediately under said exudation layer, said region having a thickness
of at least 1 µm and not more than 500 µm from said portion immediately under said
exudation layer toward the interior.
4. The nitrogen-containing sintered hard alloy in accordance with claim 3, wherein the
abundance of WC is gradually increased from a portion immediately under said region
containing absolutely no or not more than 2 percent by volume of WC toward the interior
so that the volume percentage of WC reaches the average WC volume percentage of overall
said alloy at a depth within 1 mm from a portion immediately under said exudation
layer.
5. The nitrogen-containing sintered hard alloy in accordance with claim 2, wherein an
exudation layer containing a metal binder phase, mainly composed of Ni and Co, and
WC is present on an alloy surface part, and a region containing absolutely no or not
more than 2 percent by volume of WC is provided in a portion immediately under said
exudation layer, said region having a thickness of at least 1 µm and not more than
500 µm from said portion immediately under said exudation layer toward the interior.
6. The nitrogen-containing sintered hard alloy in accordance with claim 5, wherein the
abundance of WC is gradually increased from a portion immediately under said region
containing absolutely no or not more than 2 percent by volume of WC toward the interior
so that the volume percentage of WC reaches the average WC volume percentage of overall
said alloy at a depth within 1 mm from a portion immediatly under said exudation layer.
1. Stickstoffhaltige Sinter-Hartmetallegierung, welche eine harte Phase, die WC, das
ein Hauptbestandteil ist, und ein Carbid, Nitrid oder Carbonitrid mindestens eines
Übergangsmetalls, das aus den Gruppen 4A, 5A und 6A des Periodensystems ausgewählt
ist, oder ein Carbonitrid-Verbund davon enthält, eine Bindemittelphase, die Ni, Co
und unvermeidliche Verunreinigungen enthält, und eine Ausscheidungsschicht, die eine
hauptsächlich aus Ni und Co zusammengesetzte Metallbindemittelphase enthält, umfasst,
und WC in der Oberflächenschicht der Legierung vorliegt und die Ausscheidungsschicht
ihrerseits in drei Schichten in der Reihenfolge äußere Schicht, Zwischenschicht und
untere Schicht unterteilt ist, wobei die äußere Schicht mindestens 0 und höchstens
30 Vol.-% WC mit einem Rest enthält, der von einer hauptsächlich aus Co und Ni zusammengesetzten
Metallbindemittelphase gebildet ist, die Zwischenschicht mindestens 50 und höchstens
100 Vol.-% WC mit einem Rest enthält, der von einer hauptsächlich aus Co und Ni zusammengesetzten
Metallbindemittelphase gebildet ist, die untere Schicht mindestens 0 und höchstens
30 Vol.-% WC mit einem Rest enthält, der von einer hauptsächlich aus Co und Ni zusammengesetzten
Metallbindemittelphase gebildet ist, und die Dicke von äußerer und unterer Schicht
mindestens 0,1 und höchstens 10 µm und die der Zwischenschicht mindestens 0,5 und
höchstens 10 µm beträgt.
2. Stickstoffhaltige Sinter-Hartmetallegierung nach Anspruch 1, die mit einer Zone versehen
ist, die absolut kein oder höchstens 2 Vol.-% der hauptsächlich aus Co und Ni zusammengesetzten
Metallbindemittelphase in einem unmittelbar unter der Ausscheidungsschicht liegenden
Bereich enthält, wobei die Dicke der Zone mindestens 2 und höchstens 100 µm ab dem
unmittelbar unter der Ausscheidungsschicht liegenden Bereich zum Inneren beträgt.
3. Stickstoffhaltige Sinter-Hartmetallegierung nach Anspruch 1, die mit einer Zone versehen
ist, die absolut kein oder höchstens 2 Vol.-% WC in einem unmittelbar unter der Ausscheidungsschicht
liegenden Bereich enthält, wobei die Dicke der Zone mindestens 1 und höchstens 500
µm ab dem unmittelbar unter der Ausscheidungsschicht liegenden Bereich zum Inneren
beträgt.
4. Stickstoffhaltige Sinter-Hartmetallegierung nach Anspruch 3, wobei das Vorhandensein
des WC von einem Bereich, der unmittelbar unter der Zone liegt, die absolut kein oder
höchstens 2 Vol.-% WC enthält, zum Inneren allmählich zunimmt, sodass der WC-Anteil
in Vol.-% den mittleren WC-Anteil in Vol.-% der gesamten Legierung in einer Tiefe
von bis zu 1 mm ab einem unmittelbar unter der Ausscheidungsschicht liegenden Bereich
erreicht.
5. Stickstoffhaltige Sinter-Hartmetallegierung nach Anspruch 2, wobei eine Ausscheidungsschicht,
die eine hauptsächlich aus Ni und Co zusammengesetzte Metallbindemittelphase enthält,
und WC in einer Oberflächenschicht der Legierung vorhanden sind und eine Zone, die
absolut kein oder höchstens 2 Vol.-% WC enthält, in einem Bereich unmittelbar unter
der Ausscheidungsschicht vorgesehen ist, wobei die Dicke der Zone mindestens 1 und
höchstens 500 µm ab dem unmittelbar unter der Ausscheidungsschicht liegenden Bereich
zum Inneren beträgt.
6. Stickstoffhaltige Sinter-Hartmetallegierung nach Anspruch 5, wobei das Vorhandensein
des WC von einem Bereich, der unmittelbar unter der Zone liegt, die absolut kein oder
höchstens 2 Vol.-% WC enthält, zum Inneren allmählich zunimmt, sodass der WC-Anteil
in Vol.-% den mittleren WC-Anteil in Vol.-% der gesamten Legierung in einer Tiefe
von bis zu 1 mm ab einem unmittelbar unter der Ausscheidungsschicht liegenden Bereich
erreicht.
1. Alliage dur fritté contenant de l'azote incluant une phase dure contenant WC servant
d'élément essentiel et un carbure, un nitrure ou un carbonitrure d'au moins un métal
de transition choisi parmi les groupes 4A, SA et 6A du tableau périodique ou un carbonitrure
composite de celui-ci, et une phase de liant contenant Ni, Co et des impuretés inévitables,
une couche d'exsudation contenant une phase de liant métallique, composée principalement
de Ni, Co et WC étant présente sur une partie de surface de l'alliage, ladite couche
d'exsudation étant divisée à l'intérieur en trois couches dans l'ordre d'une couche
externe, d'une couche intermédiaire et d'une couche inférieure, ladite couche externe
contenant au moins 0 % en volume et pas plus de 30 % en volume de WC, le reste étant
formé par une phase de liant métallique composée principalement de Co et Ni, ladite
couche intermédiaire contenant au moins 50 % en volume et pas plus de 100 % en volume
de WC, le reste étant formé par une phase de liant métallique composée principalement
de Co et Ni, ladite couche inférieure contenant au moins 0 % en volume et pas plus
de 30 % en volume de WC, le reste étant formé par une phase de liant métallique composée
principalement de Co et Ni, lesdites couches externe et inférieure ayant une épaisseur
d'au moins 0,1 µm et pas supérieure à 10 µm, ladite couche intermédiaire ayant une
épaisseur d'au moins 0,5 µm et pas supérieure à 10 µm.
2. Alliage dur fritté contenant de l'azote selon la revendication 1 comportant une région
ne contenant absolument pas ou pas plus de 2 % en volume de ladite phase de liant
métallique composée principalement de Co et Ni dans une partie située juste au-dessous
de ladite couche d'exsudation, ladite région ayant une épaisseur d'au moins 2 µm et
pas supérieure à 100 µm depuis ladite partie située juste sous ladite couche d'exsudation
en direction de l'intérieur.
3. Alliage dur fritté contenant de l'azote selon la revendication 1 comportant une région
ne contenant absolument pas ou pas plus de 2 % en volume de WC dans une partie située
juste sous ladite couche d'exsudation, ladite région ayant une épaisseur d'au moins
1 µm et pas supérieure à 500 µm depuis ladite partie située juste sous ladite couche
d'exsudation en direction de l'intérieur.
4. Alliage dur fritté contenant de l'azote selon la revendication 3, où l'abondance de
WC augmente progressivement depuis une partie située juste sous ladite région ne contenant
absolument pas ou pas plus de 2 % en volume de WC en direction de l'intérieur de sorte
que le pourcentage volumique de WC atteint le pourcentage volumique de WC moyen de
l'ensemble dudit alliage à une profondeur voisine de 1 mm depuis une partie située
juste sous ladite couche d'exsudation.
5. Alliage dur fritté contenant de l'azote selon la revendication 2, où une couche d'exsudation
contenant une phase de liant métallique, composée principalement de Ni et Co, et WC
et présente sur une partie de surface de l'alliage, et une région ne contenant absolument
pas ou pas plus de 2 % en volume de WC et présente dans une partie située juste sous
ladite couche d'exsudation, ladite région ayant une épaisseur d'au moins 1 µm et pas
supérieure à 500 µm depuis ladite partie située juste sous ladite couche d'exsudation
en direction de l'intérieur.
6. Alliage dur fritté contenant de l'azote selon la revendication 5, où l'abondance de
WC augmente progressivement depuis une partie située juste sous ladite région ne contenant
absolument pas ou pas plus de 2 % en volume de WC en direction de l'intérieur de sorte
que le pourcentage volumique de WC atteint le pourcentage volumique de WC moyen de
l'ensemble dudit alliage à une profondeur voisine de 1 mm depuis une partie située
juste sous ladite couche d'exsudation.