U.S. patent application number 14/106179 was filed with the patent office on 2014-04-03 for coating material for aluminum die casting mold and method of manufacturing the coating material.
This patent application is currently assigned to KIA MOTORS CORPORATION. The applicant listed for this patent is Hyundai Motor Company, Kia Motors Corporation. Invention is credited to Sung-Chul Cha, Dong-Ha Kang.
Application Number | 20140093642 14/106179 |
Document ID | / |
Family ID | 50040574 |
Filed Date | 2014-04-03 |
United States Patent
Application |
20140093642 |
Kind Code |
A1 |
Cha; Sung-Chul ; et
al. |
April 3, 2014 |
COATING MATERIAL FOR ALUMINUM DIE CASTING MOLD AND METHOD OF
MANUFACTURING THE COATING MATERIAL
Abstract
Disclosed is a coating material for an aluminum die casting mold
and a method of manufacturing the coating material. The coating
material includes a CrN bonding layer formed on a surface of a
substrate, a TiAlN/CrN nano multi-layer disposed on a surface of
the CrN bonding layer, and a TiAlN/CrSi(C)N nano multi-layer
disposed on a surface of the TiAlN/CrSiCN nano multi-layer. The
coating material for an aluminum die casting mold may maintain the
physical properties of a mold under a high temperature environment
due to the superior seizure resistance, heat resistance and
high-temperature stability of the coating material, thereby
extending the lifespan of the mold.
Inventors: |
Cha; Sung-Chul; (Seoul,
KR) ; Kang; Dong-Ha; (Seoul, KR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Kia Motors Corporation
Hyundai Motor Company |
Seoul
Seoul |
|
KR
KR |
|
|
Assignee: |
KIA MOTORS CORPORATION
Seoul
KR
HYUNDAI MOTOR COMPANY
Seoul
KR
|
Family ID: |
50040574 |
Appl. No.: |
14/106179 |
Filed: |
December 13, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
13718671 |
Dec 18, 2012 |
|
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14106179 |
|
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Current U.S.
Class: |
427/135 |
Current CPC
Class: |
C23C 14/352 20130101;
B22C 3/00 20130101; C23C 14/0664 20130101; C23C 14/32 20130101;
Y10T 428/24975 20150115; Y10T 428/265 20150115; C23C 14/0641
20130101; C23C 14/024 20130101; C23C 14/022 20130101; C23C 28/042
20130101; B22D 17/2209 20130101; C23C 28/42 20130101; C09D 1/00
20130101 |
Class at
Publication: |
427/135 |
International
Class: |
B22D 17/22 20060101
B22D017/22 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 7, 2012 |
KR |
10-2012-86083 |
Claims
1-3. (canceled)
4. A method of manufacturing a coating material for an aluminum die
casting mold, comprising: depositing a CrN bonding layer on a
surface of a substrate using a Cr target in response to forming a
nitrogen gas (N.sub.2) atmosphere by projecting nitrogen gas
(N.sub.2) through a gas inlet of a chamber; depositing a TiAlN/CrN
nano multi-layer on a surface of the deposited CrN bonding layer
using a TiAl target and the Cr target; and depositing a TiAlN/CrSiN
nano multi-layer on a surface of the deposited TiAlN/CrN nano
multi-layer using the TiAl target and a CrSi target.
5. The method of claim 4, wherein the depositing of the
TiAlN/CrSiCN nano multi-layer further comprises depositing the
TiAlN/CrSiN nano multi-layer to a thickness of about 0.5 to 5
.mu.m.
6. The method of claim 5, wherein the depositing of the CrN bonding
layer further comprises: depositing the CrN bonding layer to a
thickness of about 0.5 to 5 .mu.m, and the depositing of the
TiAlN/CrN nano multi-layer further comprises depositing the
TiAlN/CrN nano multi-layer to a thickness of about 0.5 to 5
.mu.m.
7. The method of claim 4, wherein the depositing of the TiAlN/CrN
nano multi-layer further comprises depositing the TiAlN/CrN nano
multi-layer (120) to obtain a ratio of 1:1:1: of the Ti, Al and Cr
in the TiAlN/CrN nano multi-layer.
8. The method of claim 4, wherein the depositing of the TiAlN/CrSiN
nano multi-layer further comprises depositing the TiAlN/CrSiN nano
multi-layer to obtain a ratio of 1:1:0.9:0.1 of the Ti, Al, Cr and
Si in the TiAlN/CrSiN nano multi-layer.
9. The method of claim 4, wherein the deposition is performed using
a physical vapor deposition method.
10. A method of manufacturing of the coating material for an
aluminum die casting mold, comprising: depositing a CrN bonding
layer on a surface of a substrate using a Cr target in response to
forming a nitrogen gas (N.sub.2) atmosphere by projecting nitrogen
gas (N.sub.2) through a gas inlet of a chamber; depositing a
TiAlN/CrN nano multi-layer on a surface of the deposited CrN
bonding layer using a TiAl target and the Cr target; and depositing
a TiAlN/CrSiCN nano multi-layer on a surface of the deposited
TiAlN/CrN nano multi-layer using the TiAl target and a CrSi target
in response to forming an acetylene gas (C.sub.2H.sub.2) atmosphere
by projecting acetylene gas (C.sub.2H.sub.2) through the gas inlet
of the chamber.
11. The method of claim 10, wherein the depositing of the
TiAlN/CrSiCN nano multi-layer further comprises depositing the
TiAlN/CrSiN nano multi-layer to a thickness of about 0.5 to 5
.mu.m.
12. The method of claim 11, wherein the depositing of the CrN
bonding layer further comprises depositing the CrN bonding layer to
a thickness of about 0.5 to 5 .mu.m, and the depositing of the
TiAlN/CrN nano multi-layer further comprises by depositing the
TiAlN/CrN nano multi-layer to a thickness of about 0.5 to 5
.mu.m.
13. The method of claim 10, wherein the depositing of the TiAlN/CrN
nano multi-layer further comprises depositing the TiAlN/CrN nano
multi-layer to obtain a ratio of 1:1:1 of the Ti, Al and Cr in the
TiAlN/CrN nano multi-layer.
14. The method of claim 10, wherein the depositing of the
TiAlN/CrSiCN nano multi-layer is performed by depositing the
TiAlN/CrSiCN nano multi-layer so that Ti, Al, Cr, Si and C in the
TiAlN/CrSiCN nano multi-layer amount to a ratio of
1:1:0.8:0.1:0.1.
15. The method of claim 10, wherein the deposition is executed
using a physical vapor deposition method.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application claims priority under 35 U.S.C. .sctn.119
to Korean Patent Application No. 10-2012-86083, filed on Aug. 7,
2012, in the Korean Intellectual Property Office, the disclosure of
which is incorporated herein by reference in its entirety.
BACKGROUND
[0002] 1. Technical Field
[0003] This invention relates to a coating material for an aluminum
die casting mold and a method of manufacturing the coating
material, more particularly, to a coating material for an aluminum
die casting mold, having a multi-layered structure including a CrN
bonding layer, a TiAlN/CrN nano multi-layer, a TiAlN/CrSiN or
TiAlN/CrSiCN nano multi-layer, and showing improved seizure
resistance and durability of a mold, and a method of manufacturing
the coating material.
[0004] 2. Background of the Invention
[0005] In recent years, as manufacturing processes have become
automated and executed at high speeds, various metal materials such
as molds, mechanical structures, etc., are used under more severe
conditions.
[0006] In particular, an aluminum die casting mold requires a high
level of physical properties due to a continuous high load and high
impact, thus the lifespan of an aluminum die casting mold is
determined by the mold materials, mold designs, working conditions,
heat treatment of a mold, and surface treatment, etc. The lifespan
decreases due to heat checking by thermal shock, seizure and
wearing by molten aluminum, and heat softening caused by the high
temperature working environment (e.g., up to 750.degree. C.), and
on the like.
[0007] Thus, various attempts have been made to prevent shortening
of mold lifespan and to maintain mold performance. Specifically,
active research has been widely conducted to develop coating
materials with superior physical properties such as seizure
resistance, wear resistance, low wear property, heat resistance,
acid resistance, and the like.
[0008] For a typical mold, a nitride or carbide based on Titanium
(Ti), Chromium (Cr), etc., is used as a surface protective coating
material. In particular, in=an aluminum die casting mold, titanium
aluminum nitride (TiAlN) or aluminum chrome nitride (AlCrN) is
typically used as a coating material. However, TiAlN does not have
sufficient heat resistance to be used as a coating material for an
aluminum die casting mold which is exposed to a high-temperature
environment of up to about 750.degree. C., and has poor heat
stability, for example, showing poor physical properties when
exposed to a high temperature environment.
[0009] Additionally, AlCrN has relatively superior heat resistance
compared to TiAlN, but has inferior seizure resistance, so a molten
alloy such as aluminum may be easily attached to a surface of a
mold, resulting in shortened lifespan of the mold and a decrease in
quality of a cast iron product.
[0010] The description provided above as a related art of the
present invention is just for helping understanding the background
of the present invention and should not be construed as being
included in the related art known by those skilled in the art.
SUMMARY
[0011] The present invention has been proposed to solve the above
drawbacks and provides a coating material for an aluminum die
casting mold, having superior heat resistance, high temperature
stability and seizure resistance compared to a conventional
Titanium Aluminum Nitride (TiAlN) or Aluminum Chromium Nitride
(AlCrN) coating material, and thus can extend the lifespan of a
mold, and a method of manufacturing the coating material.
[0012] A coating material for an aluminum die casting mold
according to an embodiment of the present invention includes a
Chromium Nitride (CrN) bonding layer formed on a surface of a
substrate, a TiAlN/CrN nano multi-layer disposed on a surface of
the CrN bonding layer, and a TiAlN/CrSi(C)N (Chromium Silicide
Carbon Nitride) nano multi-layer disposed on a surface of the
TiAlN/CrN nano multi-layer.
[0013] In addition, the TiAlN/CrSi(C)N nano multi-layer may have a
thickness of 0.5 to 5 .mu.m. The CrN bonding layer and the
TiAlN/CrN nano multi-layer may have thicknesses of 0.5 to 5 .mu.m,
respectively.
[0014] A method of manufacturing a coating material for an aluminum
die casting mold according to an embodiment of the present
invention includes depositing a CrN bonding layer on a surface of a
substrate using a Cr target in response to forming a nitrogen
atmosphere by projecting nitrogen gas through a gas inlet,
depositing a TiAlN/CrN nano multi-layer on a surface of the
deposited CrN bonding layer using a TiAl target and a Cr target,
and depositing a TiAlN/CrSiN nano multi-layer on a surface of the
deposited TiAlN/CrN nano multi-layer using a TiAl target and a CrSi
target.
[0015] A method of manufacturing a coating material for an aluminum
die casting mold according to an embodiment of the present
invention includes depositing a CrN bonding layer on a surface of a
substrate using a Cr target in response to forming a nitrogen
atmosphere by projecting nitrogen gas through a gas inlet,
depositing a TiAlN/CrN nano multi-layer on a surface of the
deposited CrN bonding layer using a TiAl target and a Cr target,
and depositing a TiAlN/CrSiN nano multi-layer on a surface of the
deposited TiAlN/CrN nano multi-layer using a TiAl target and a CrSi
target in response to forming an acetylene gas (C.sub.2H.sub.2)
atmosphere by projecting acetylene gas (C.sub.2H.sub.2) through a
gas inlet.
[0016] In addition, the depositing of the TiAlN/CrSiN nano
multi-layer may be performed by depositing the TiAlN/CrSiN nano
multi-layer to a thickness of about 0.5 to 5 .mu.m. The depositing
of the TiAlN/CrSiCN nano multi-layer may be performed by depositing
the TiAlN/CrSiCN nano multi-layer to a thicknesses of about 0.5 to
5 .mu.m. The depositing of the CrN bonding layer may be performed
by depositing the CrN bonding layer to a thicknesses of about 0.5
to 5 .mu.m, and the depositing of the TiAlN/CrN nano multi-layer
may be performed by depositing the TiAlN/CrN nano multi-layer to a
thicknesses of about 0.5 to 5 .mu.m.
[0017] Furthermore, the depositing of the TiAlN/CrN nano
multi-layer may be performed by depositing the TiAlN/CrN nano
multi-layer wherein a ratio of Ti, Al and Cr in the TiAlN/CrN nano
multi-layer is 1:1:1. The depositing of the TiAlN/CrSiN nano
multi-layer may be performed by depositing the TiAlN/CrSiN nano
multi-layer wherein a ratio Ti, Al, Cr and Si in the TiAlN/CrSiN
nano multi-layer is 1:1:0.9:0.1. The depositing of the TiAlN/CrSiCN
nano multi-layer may be performed by depositing the TiAlN/CrSiCN
nano multi-layer wherein a ratio of Ti, Al, Cr, Si and C in the
TiAlN/CrSiCN nano multi-layer is 1:1:0.8:0.1:0.1.
[0018] Furthermore, the deposition may be performed using a
physical vapor deposition (PVD) method.
BRIEF DESCRIPTION OF THE DRAWINGS
[0019] The above and other features of the present invention will
now be described in detail with reference to exemplary embodiments
thereof illustrated the accompanying drawings which are given
hereinbelow by way of illustration only, and thus are not
limitative of the present invention, and wherein:
[0020] FIG. 1 is an exemplary image showing a seizure on a core fin
of an aluminum die casting mold, according to the related art;
[0021] FIG. 2 is an exemplary diagram showing a structure of a
TiAlCrSi(C)N coating material, according to an exemplary embodiment
of the present invention;
[0022] FIG. 3 is an exemplary diagram showing a physical vapor
deposition (PVD) system used to manufacture the coating material
according to an exemplary embodiment of the present invention;
[0023] FIG. 4 is an exemplary image showing a mold coated with a
conventional TiAlN coating material, washed with sodium hydroxide
after being dipped and rotated in an aluminum molten metal for 6
hours;
[0024] FIG. 5 is an exemplary image showing a mold coated with a
conventional AlCrN coating material, washed with sodium hydroxide
after dipped and rotated in an aluminum molten metal for 6
hours;
[0025] FIG. 6 is an exemplary image showing a mold coated with the
coating material according to an exemplary embodiment of the
present invention, washed with sodium hydroxide after dipped and
rotated in an aluminum molten metal for 6 hours; and
[0026] FIG. 7 is an exemplary image showing a mold coated with the
coating material according to an exemplary embodiment of the
present invention, washed with sodium hydroxide after dipped and
rotated in an aluminum molten metal for 27 hours.
DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENT
[0027] The terminology used herein is for the purpose of describing
particular embodiments only and is not intended to be limiting of
the invention. As used herein, the singular forms "a", "an" and
"the" are intended to include the plural forms as well, unless the
context clearly indicates otherwise. It will be further understood
that the terms "comprises" and/or "comprising," when used in this
specification, specify the presence of stated features, integers,
steps, operations, elements, and/or components, but do not preclude
the presence or addition of one or more other features, integers,
steps, operations, elements, components, and/or groups thereof. As
used herein, the term "and/or" includes any and all combinations of
one or more of the associated listed items.
[0028] Unless specifically stated or obvious from context, as used
herein, the term "about" is understood as within a range of normal
tolerance in the art, for example within 2 standard deviations of
the mean. "About" can be understood as within 10%, 9%, 8%, 7%, 6%,
5%, 4%, 3%, 2%, 1%, 0.5%, 0.1%, 0.05%, or 0.01% of the stated
value. Unless otherwise clear from the context, all numerical
values provided herein are modified by the term "about."
[0029] The term "TiAlCrSi(C)N" used in the present invention is
referred to as "TiAlCrSiN" or "TiAlCrSiCN" and the term
"TiAlN/CrSi(C)N" used herein is referred to as "TiAlN/CrSiN" or
"TiAlN/CrSiCN."
[0030] Embodiments of the present invention will be described below
in detail with reference to the accompanying drawings.
[0031] FIG. 1 is an exemplary image showing an occurrence of
seizure on a core fin of an aluminum die casting mold. As shown in
FIG. 1, when casting is performed using an aluminum die casting
mold, a seized product 10 is generated from an aluminum molten
metal. The seized product 10 may reduce the hardness of a surface
of the mold, and may cause leaks, damage of a mold, etc., thereby
shortening the lifespan of the mold.
[0032] Moreover, an aluminum die casting mold generally requires a
high level of physical properties to endure severe conditions
caused by ultra high pressure and high cycle. TiAlN or AlCrN used
as a conventional coating material may exhibit poor heat
resistance, high temperature stability, seizure resistance, etc.,
and thus has limitations in extending the lifespan of a mold.
Therefore, the present invention provides a TiAlCrSi(C)N coating
material.
[0033] FIG. 2 is a diagram showing a structure of a TiAlCrSi(C)N
coating material according to the present invention. As shown in
FIG. 2, the coating material according to an exemplary embodiment
of the present invention may include a CrN bonding layer 110 formed
on a surface of a substrate 100, a TiAlN/CrN nano multi-layer 120
disposed on a surface of the CrN bonding layer 110 configured to
support a functional layer, and the functional layer TiAlN/CrSi(C)N
nano multi-layer 130 disposed on a surface of the TiAlN/CrN nano
multi-layer 120.
[0034] Furthermore, the substrate of the aluminum die casting mold
may further include a nitride layer having a thickness of 80 to 120
.mu.m through a nitrification process when necessary.
[0035] Moreover, the CrN bonding layer 110 is widely used for its
high chemical stability such as anti-corrosiveness and for its
mechanical properties such as hardness, friction resistance,
lubrication property, etc. Therefore, in the present invention, the
CrN bonding layer 110 may be used as a bonding layer to minimize
residual stress and improve toughness, fatigue resistance, impact
resistance, etc.
[0036] In addition, the TiAlN/CrN nano multi-layer 120 may be used
as a supporting layer to improve characteristics such as heat
resistance, acid resistance, seizure resistance, etc., required for
an aluminum die casting mold. The TiAlN/CrSi(C)N nano multi-layer
130 may be used as a functional layer to improve heat resistance,
acid resistance, wear resistance, low friction at high temperature
and seizure resistance a characteristic of the coating material of
the present invention.
[0037] In other words, wear resistance and impact resistance are
conflicting properties, which may be improved using the CrN bonding
layer 110 having high impact resistance together with the TiAlN/CrN
nano multi-layer 120 and the TiAlN/CrSi(C)N nano multi-layer 130,
both of which have high impact resistance.
[0038] Further, the CrN bonding layer 110 may have a thickness of
about 0.5 to 5 .mu.m. When the thickness is less than about 0.5
.mu.m, insufficient quantities of constituent materials may cause a
decrease in effectiveness of the resistances, whereas, when the
thickness exceeds about 0.5 .mu.m, the coating layer may be peeled
off.
[0039] In addition, the TiAlN/CrN nano multi-layer 120 and the
TiAlN/CrSi(C)N nano multi-layer 130 may have thicknesses of about
0.5 to 5 .mu.m, respectively. When the thicknesses are less than
about 0.5 .mu.m, the two different layers may mix causing
difficulty in forming the multi-layered structure, and thereby
reducing the qualities of the materials. On the other hand, when
the thicknesses exceed about 0.5 .mu.m, matched transformation
between two layers may be destroyed, thereby degrading the
hardness.
[0040] Methods of coating a surface of a metal substrate with a
coating material may be classified into a PVD method and a chemical
vapor deposition (CVD) method. PVD is a dry processing method that
provides negative polarity to a target material (e.g., substrate)
and deposits an ionized metal material on a surface of the material
while supplying the ionized metal in a vapor state. In the PVD
method, the ionized metal material may be uniformly coated onto the
surface of the substrate, and the adhesiveness may be improved
using fine ion particles.
[0041] In other words, in the present invention, the PVD method
uses arc, high power impulse magnetron sputtering (HIPIMS) and
inductive coupled plasma (ICP) to obtain a nano level deposition
and high speed coating of coating material particles.
[0042] FIG. 3 is an exemplary diagram showing a PVD system used to
manufacture the coating material according to the present
invention. As shown in FIG. 3, the PVD system may include a chamber
200; a pump 210, a Cr target 220, a TiAl target 230, a CrSi target
240, and a gas inlet 250; and a heating unit 260, installed on the
chamber 200; and a mold (e.g., a substrate) mounted to a rotary
holder 270 within the chamber 200.
[0043] As a coating pre-treatment process, the interior of the
chamber 200 may be converted into a vacuum state using a pump 210,
and converted into a plasma state by projecting argon gas through a
gas inlet 250.
[0044] Moreover, the surface of the substrate 100 may be cleaned
and activated by heating the chamber 200 to about 80.degree. C.
using the heating unit 260 and by applying a predetermined voltage
to the mold to allow positive argon ions to collide with a surface
of the mold. Furthermore, a nitrogen gas (N.sub.2) atmosphere may
be formed by projecting nitrogen gas (N.sub.2) in the chamber 200
through the gas inlet 250, and a CrN bonding layer 110 may be
deposited to a thickness of about 0.5 to 5 .mu.m by supplying Cr
ions to the surface of the substrate 100 using a Cr target 220.
[0045] In addition, by selectively exposing the mold onto which the
CrN bonding layer 110 is deposited to a TiAl target 230 configured
to provide Ti and Al ions and a Cr target 220 configured to provide
Cr ions using a rotary holder 270, a TiAlN/CrN nano multi-layer
120, having a structure in which TiAlN layers and CrN layers are
alternatively stacked on a surface of the CrN bonding layer 110,
may be deposited to a thickness of about 0.5 to 5 .mu.m.
[0046] The TiAlN/CrN nano multi-layer 120 may be a supporting layer
configured to improve heat resistance, acid resistance, wear
resistance and toughness of the substrate 100, and may be deposited
to create a ratio of Ti, Al and Cr in the TiAlN/CrN nano
multi-layer 120 to be 1:1:1 according to alternative stacking of
the respective layers to maximize the heat resistance, acid
resistance, wear resistance, and toughness of the substrate.
[0047] Further, by selectively exposing the mold onto which the
TiAlN/CrN nano multi-layer 120 is deposited to the TiAl target 230
configured to provide Ti and Al ions and a CrSi target 240
configured to provide Cr and Si ions, the TiAlN/CrN nano
multi-layer 120, having a structure in which TiAlN layers and CrN
layers are alternatively stacked on a surface of the TiAlN/CrN nano
multi-layer 120, may be deposited to a thickness of about 0.5 to 5
.mu.m. When the above-described processes are performed in response
to forming the acetylene gas (C.sub.2H.sub.2) atmosphere in the
chamber 200 by projecting acetylene gas (C.sub.2H.sub.2) in the
chamber 200 through the gas inlet 250, the TiAlN/CrSiCN nano
multi-layer, having a structure in which TiAlN layers and CrSiCN
layers are alternatively stacked on the surface of the TiAlN/CrN
nano multi-layer 120, may be deposited with supplied carbons
(C).
[0048] The TiAlN/CrSi(C)N nano multi-layer 130 may be a functional
layer configured to improve heat resistance, acid resistance, wear
resistance, low friction at high temperature and seizure
resistance, a property of the coating material according to the
present invention. Due to the alternating stacking of the
respective layers to maximize the above described effects, the
TiAlN/CrSi(C)N nano multi-layer 130 may be deposited to create a
ratio Ti, Al, Cr, Si and (C) to be 1:1:(0.8 to) 0.9: 0.1:(0.1).
TABLE-US-00001 TABLE 1 Comparative Comparative Embodiment 1
Embodiment 2 Embodiment 1 Surface treatment/coating TiAlN AlCrN
TiAlCrSiCN Method PVD PVD PVD Thickness (.mu.m) 9.5 (5 CrN-4.5 9.8
(5 CrN-4.8 9.7 (5 CrN/3.7 TiAlN) AlCrN) TiAlCrN-1 TiAlCrCN)
Adhesiveness (N) 49.2 48.3 51 Hardness (HV) 3,179 3,252 3,367
Hardness (HV) after left 2,850 3,213 3,359 at high temperature
Oxidation 850 900 950 Temperature (.degree. C.) Seizure resistance
Normal Poor Excellent
[0049] Table 1 lists the results obtained through comparison of
TiAlCrSiCN coating material according to an exemplary embodiment of
the present invention with conventional TiAlN and AlCrN coating
materials.
[0050] The hardness was measured by inserting an indenter into a
specimen at an ultra low load; the adhesiveness was measured under
a load when the layers began to peel off when increasing the load
applied to a diamond tip by applying forces to the coated surface
using the diamond tip to make a row of grooves; the thickness was
measured using a trajectory made by pressurizing a coated surface
under uniform load using iron beads; the oxidation temperature was
measured as temperature obtained when the thickness of an oxidized
layer formed through oxidation reached about 200 nm in response to
maintaining the temperature at a particular temperature under an
N.sub.2-20% O.sub.2 atmosphere in a high temperature chamber; and
the variation in hardness was measured in response to maintaining a
high temperature of about 700.degree. C. under an N.sub.2-20%
O.sub.2 atmosphere in the chamber.
[0051] As listed in Table 1, the oxidation temperature of the
coating material according to the present invention was 950.degree.
C., which was higher than the oxidation temperatures of the TiAlN
and AlCrN coating materials, indicating that the coating material
according to the present invention has higher heat resistance than
the conventional coating materials. Additionally, the hardness of
the coating material according to the present invention was 3367
HV, and the hardness in response to maintaining a high temperature
was 3359 HV, showing less changes in physical properties compared
to those of the conventional coating materials, indicating that the
coating material according to the present invention has higher high
temperature stability than the conventional coating materials.
[0052] FIG. 4 is an exemplary image showing a mold coated with a
conventional TiAlN coating material, washed with sodium hydroxide
after being dipped and rotated in an aluminum molten metal for 6
hours. FIG. 5 is exemplary an image showing a mold coated with a
conventional AlCrN coating material, washed with sodium hydroxide
after being dipped and rotated in an aluminum molten metal for 6
hours. FIG. 6 is an exemplary image showing a mold coated with the
coating material of the present invention, washed with sodium
hydroxide after being dipped and rotated in an aluminum molten
metal for 6 hours. FIG. 7 is exemplary an image showing a mold
coated with the coating material of the present invention, washed
with sodium hydroxide after being dipped and rotated in an aluminum
molten metal for 27 hours.
[0053] Furthermore, the sodium hydroxide may be used to remove an
aluminum-seized product. In the molds coated with conventional
coating materials, surface defects were observed on the mold.
However, surface defects were not observed on the mold coated with
the coating material of the present invention. Surface defects were
not observed on the mold coated with the coating material of the
present invention due to the seizure resistance of the mold
improving through use of the coating material of the present
invention, and due to the presence of the TiAlN/CrSi(C)N nano
multi-layer.
[0054] As described above, the coating material of the present
invention has superior physical properties such as acid resistance,
heat resistance, hardness and seizure resistance compared to the
conventional coating materials, and thus may be useful in extending
the lifespan of an aluminum die casting mold, resulting in various
effects of reducing a mold maintenance cost and improving
productivity, etc.
[0055] In general, seizure resistance means a property of
preventing some of a molten metal from attaching to the mold during
a casting process. Accordingly, the coating material of the present
invention can be useful in improving quality and productivity of a
cast-iron product due to the high seizure resistance compared to a
conventional TiAlN or AlCrN coating material.
[0056] The invention has been described in detail with reference to
exemplary embodiments thereof. However, it will be appreciated by
those skilled in the art that changes or modifications may be made
in these embodiments without departing from the principles of the
invention, the scope of which is defined in the accompanying claims
and their equivalents.
* * * * *