U.S. patent application number 10/479881 was filed with the patent office on 2005-01-13 for process for the production of a titanium alloy based composite material reinforced with titanium carbide, and reinforced composite material obtained thereby.
Invention is credited to Testani, Claudio.
Application Number | 20050008524 10/479881 |
Document ID | / |
Family ID | 11455579 |
Filed Date | 2005-01-13 |
United States Patent
Application |
20050008524 |
Kind Code |
A1 |
Testani, Claudio |
January 13, 2005 |
Process for the production of a titanium alloy based composite
material reinforced with titanium carbide, and reinforced composite
material obtained thereby
Abstract
Object of the present invention is a process for the production
of a Titanium alloy based composite material with satisfactory
mechanical features at high temperature, characterised in that
Titanium alloy powders and Titanium carbide powders are blended,
hot-pressed and hot-rolled or extruded. The invention also
encompasses a composite material obtainable with said process.
Inventors: |
Testani, Claudio; (Rome,
IT) |
Correspondence
Address: |
DeLio & Peterson
121 Whitney Avenue
New Haven
CT
06510
US
|
Family ID: |
11455579 |
Appl. No.: |
10/479881 |
Filed: |
June 10, 2004 |
PCT Filed: |
June 3, 2002 |
PCT NO: |
PCT/IT02/00358 |
Current U.S.
Class: |
419/17 ;
419/49 |
Current CPC
Class: |
B22F 2998/10 20130101;
B22F 2999/00 20130101; B22F 1/0003 20130101; B22F 3/15 20130101;
B22F 1/0003 20130101; B22F 3/20 20130101; B22F 2201/11 20130101;
B22F 3/18 20130101; B22F 9/082 20130101; B22F 2998/00 20130101;
C22C 32/0052 20130101; B22F 2999/00 20130101; B22F 2998/00
20130101; B22F 2998/10 20130101; C22C 1/1094 20130101 |
Class at
Publication: |
419/017 ;
419/049 |
International
Class: |
B22F 003/24 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 8, 2001 |
IT |
RM2001A000320 |
Claims
1. A process for the production of a Titanium alloy based composite
material having satisfactory mechanical features at high
temperature, in which a Titanium alloy powder and a Titanium
carbide powder are blended, hot-compacted and hot-rolled, or
extruded, characterised in that the hot compacting is obtained by
isostatic hot pressing at a temperature ranging from 850 to
950.degree. C., at a pressure ranging from 80 to 130 MPa, for a
time less than four hours, and the resulting material is heated to
a temperature of about 1000.degree. C. and pressed to provide a
thickness reduction of from 5 to 50%.
2. The process for the production of a Titanium alloy based
composite material having satisfactory mechanical features at high
temperature according to claim 1, wherein the concentration of the
Titanium carbide expressed in percent by weight ranges from 0.5 to
30%.
3. The process for the production of a Titanium alloy based
composite material having satisfactory mechanical features at high
temperature according to claim 1, wherein the particle size of the
Titanium alloy is less than 250 .mu.m.
4. The process for the production of a Titanium alloy based
composite material having satisfactory mechanical features at high
temperature according to claim 3, wherein the particle size of
Titanium carbide is less than 5 .mu.m.
5. The process for the production of a Titanium alloy based
composite material having satisfactory mechanical features at high
temperature according to claim 1, wherein the blending of the said
two powders is carried out in the presence of 50% by volume acetone
or of an anti-clumping agent, optionally added separately to each
of the powders to be blended.
6. The process for the production of a Titanium alloy based
composite material having satisfactory mechanical features at high
temperature according to claim 1, wherein the blending of the two
powders is carried out under inert gas, preferably Argon,
atmosphere.
7. The process for the production of a Titanium alloy based
composite material having satisfactory mechanical features at high
temperature according to claim 6, wherein the blending is obtained
by revolving a vessel, containing the two powders, at a high rate
for a time ranging from 5 minutes to 8 hours.
8. The process for the production of a Titanium alloy based
composite material having satisfactory mechanical features at high
temperature according to claim 7, wherein the blended powders are
dried under vacuum.
9. The process for the production of a Titanium alloy based
composite material having satisfactory mechanical features at high
temperature according to any of the preceding claims, wherein the
resulting compound is hot-rolled in the range from 800 to
1000.degree. C. with less than 5% reduction passages, until the
desired total thickness is achieved.
10. The process for the production of a Titanium alloy based
composite material having satisfactory mechanical features at high
temperature according to claim 9, wherein the total thickness
reduction is of about 80%.
11. A Titanium alloy based composite material reinforced with
Titanium carbide, as obtained by the process of claim 1.
Description
[0001] The present invention refers to the production of components
obtained from Titanium alloy based components, to be used in the
field of mechanics and of high temperature automotives in the
presence of creep and of high specific stresses.
[0002] EP-0 215 941 (Dynamet) teaches the manufacturing, by
blending and sintering, of Titanium-based composite materials
including a dispersion of Titanium carbide (TiC) powder. The end
product obtained is free of a significant reaction at the
TiC-matrix interface or of dilution regions exhibiting a
composition gradient.
[0003] The main restriction of this US process is that the product
obtained has an interface exhibiting scarce chemical reaction, and
therefore where the stresses are accordingly transferred by
mechanical mechanisms. Moreover, exposure to high temperatures
fosters grain growth, a phenomenon that worsens the mechanical
properties, especially the fatigue strength.
[0004] Therefore, in the specific field there subsists the demand
for a manufacturing process allowing to overcome the abovementioned
drawbacks.
[0005] The process subject of the present invention surmounts all
of the abovementioned drawbacks, further providing other advantages
that will be mentioned hereinafter.
[0006] In fact, object of the present invention is a process for
the production of a Titanium alloy based composite material having
satisfactory mechanical features at high temperature, wherein a
Titanium alloy powder and a Titanium carbide powder are blended,
hot-compacted and hot-rolled or extruded.
[0007] The TiC content (concentration) can range from 0.5 to 30%
b/w.
[0008] The granulometry of the Titanium alloy can be <250 .mu.m,
preferably <5 .mu.m.
[0009] The blending of the two powders may be carried out in the
presence of the 50% b/v acetone (or other anti-clumping agent),
optionally added separately to each one of the powders to be
blended, prior to blending.
[0010] The powder blending may be carried out under inert gas,
e.g., Argon, atmosphere.
[0011] The blending may be obtained by revolving in a vessel,
containing the two powder types, at a high rate of rpm for a time
ranging from 5 minutes to 8 hours.
[0012] The hot compacting may be obtained by hot isostatic pressing
(HIP) at temperatures ranging from 850 to 950.degree. C., at
pressures ranging from 80 to 130 MPa, for <4 h times.
[0013] The powders thus blended can be dried substantially under
vacuum.
[0014] The material resulting from the hot pressing is preferably
heated to a temperature of about 1000.degree. C. and pressed to a
thickness reduction of from 5 to 50%.
[0015] The yielded pressed product is rolled, at temperatures
comprised in the range 800-1000.degree. C., with <5% reduction
passages, down to the desirable total thickness reduction, e.g. of
about 80%.
[0016] The process according to the present invention allows an
optimum distribution of the TiC particulate and the diffusion
thereof at the interface with the Titanium alloy matrix.
[0017] The diffusion is measured from a Carbon (C) content of about
20% at 20 .mu.m from a TiC particle.
[0018] The carbon diffusion obtained by TiC particles/Titanium
alloy matrix interface reaction is controlled via the thermal
treatment of hot compacting.
[0019] In particular, in order to obtain a C content of about 17%
in atom percent, at a 20-.mu.m distance from a TiC particle, a
960.degree. C. temperature should be applied for 3 h with pressures
of about 1100 MPa.
[0020] This significant dissolving of the TiC inside of the
Titanium alloy matrix is accountable for the increase of the
mechanical properties attained with the present invention.
[0021] With respect to the composite material disclosed in EP 0 215
941, for the composite material of the present invention the
rolling step advantageously suffices to eliminate Titanium carbide
agglomerates; these carbides, very uniformly dispersed, allow to
overcome brittleness problems at room temperature, with breakaway
of the bonds at the old particle edges in the unrolled material.
The measured strength values are about 20-30% higher than those of
the composite alloy of EP 0 215 941. This advantageous result could
also be accounted for by the fact that inside of the matrix an
evident dilution of the TiC has occurred, with a C concentration
profile that drops from about the 50%, measured at the centre of a
TiC particle, and stabilizes, after about 20 .mu.m, to values of
about 5%, measured also at about 60 .mu.m from the edge of the TiC
particle.
[0022] The Titanium alloys that yielded satisfactory results as
matrices in the compounds according to the present invention are
the following. Ti6Al4V, Ti6Al2Sn4Zr2Mo0.1Si, Ti15Al3V3Sn3Cr, and
Ti6242S.
[0023] The present invention also refers to the composite material
obtainable with the hereto-described process.
[0024] So far, a general description of the present invention was
given. With the aid of the attached figures and of the following
example, a more detailed description of specific embodiments of the
invention, aimed at making better understood the objects, the
features, the advantages and the operation modes thereof will be
provided hereinafter.
[0025] FIG. 1 shows the microstructure of an embodiment of the
homogeneous blend of Titanium alloy powder and TiC powder, prior to
the hot compacting.
[0026] FIG. 2 shows the increase of the mechanical properties, at
<600.degree. C. temperatures, of a compound obtained with an
embodiment of the process according to the invention with respect
to the material obtained with the same powders by sintering and hot
compacting.
EXAMPLE
[0027] The powders to be blended according to the invention are
prepared by gas atomizing from 500 mm high, 45 mm .O slashed.
ingots. The end sizes of the particles obtained are <200 .mu.m
for the Ti6242S alloy, utilized in the example, and <10 .mu.m
for the Titanium carbide.
[0028] Table 1 shows the composition of the Titanium alloy powder
with respect to that of the starting ingot. The Table also reports
the average size (in .mu.m) of the Ti6242S powder, the flow rate
and the size (in .mu.m) of the TiC particles.
1TABLE 1 Al Sn Zn Mo O N H Ti6242S Alloy % % % % ppm ppm ppm
Pre-atomizing samples 6.1 1.4 3.7 1.6 646 218 nd Powder samples 6.3
1.3 3.8 1.7 1096 496 90 Average size (.mu.m) Flow rate TiC particle
size of Ti6242S particles (ASTMB213) (.mu.m) 44-200 28s 0.1-5
[0029] Ti6242S and TiC powders are blended in a rotary cylinder
with movable blades, instead of resorting to a mechanical alloying
that produces more superficial fractures and, therefore, more
reaction sites with C, O, N. This procedure, as well as the
mechanical alloying, provides optimum reinforcing material/matrix
homogeneousness. FIG. 1 shows the 200.times.SEM (Scanning Electron
Microscopy) microphotography of the homogenate blend.
[0030] Then, the blended powders are introduced in a steel cylinder
that is sealed and welded to the lid by TIG (Tungsten Inert Gas)
welding. The cylinder lid is provided with a port and a piping for
carrying out the evacuation. The cylinder-shaped container was
designed in order to resist fractures during the HIP process.
[0031] The evacuation takes place with a rotary pump, obtaining
vacuums in the order of 10.sup.-5 mbar.
[0032] Post-evacuation, the powder is isostatically pressed, with
ho prior consolidation, for 5 h at a 1000.degree. C. temperature
and with a pressure peak of 1500 Bar.
[0033] Then, tensile test samples of the yielded composite material
are obtained, with their axes parallel to the cylinder
generatrix.
[0034] After heating to 1100.degree. C., the composite material is
hot-rolled, with an 80% thickness reduction.
[0035] Samples of the rolled material thus obtained are subjected
to tensile tests. The test results highlight an increase of the
tensile strength of the material at <600.degree. C. temperatures
and a decrease of this parameter at >600.degree. C.
temperatures. FIG. 2 shows the increase of the mechanical
properties of the rolled composite material of the invention with
respect to that of the material merely sinterized and compacted by
HIP.
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