# Patent

## Title
Composite articles made by process for joining stainless steel part and titanium carbide ceramic part

## Abstract

A process for joining a stainless steel part and a titanium carbide ceramic part comprising: providing a SUS part, a TiC ceramic part, a Ti foil and a Fe foil; placing the TiC ceramic part, the Ti foil, the Fe foil, and the SUS part into a mold, the Ti foil and the Fe foil located between the TiC ceramic part and the SUS part, the Ti foil abutting the TiC ceramic part, the Fe foil abutting the SUS part and the Ti foil; placing the mold into a chamber of an hot press sintering device, heating the chamber and pressing the SUS part, the TiC ceramic part, the Ti foil, and the Fe foil at least until the SUS part, the TiC ceramic part, the Ti foil and the Fe foil form a integral composite article.

## Background
CROSS-REFERENCE TO RELATED APPLICATIONS
This application is related to co-pending U.S. patent application Ser. No. 13/164,281, entitled “PROCESS FOR JOINING STAINLESS STEEL PART AND SILICON CARBIDE CERAMIC PART AND COMPOSITE ARTICLES MADE BY SAME”. Such applications have the same assignee as the present application. The above-identified applications are incorporated herein by reference.
BACKGROUND
1. Technical Field
The present disclosure relates to a process for joining a metal part and a ceramic part, especially to a process for joining a stainless steel part and a titanium carbide ceramic part, and a composite article made by the process.
2. Description of the Related Art
Stainless steel has excellent corrosion resistance and abrasion resistance, and is widely applied in the components manufacturing industry. However, unlike titanium carbide, stainless steel cannot maintain its physical properties when used in an environment of high temperature and strong corrosives. Therefore, a composite article comprising a stainless steel part and a titanium carbide ceramic part has a desirable performance of high temperature resistance, corrosion resistance, abrasion resistance, and usable in extreme environments.
A typical process for joining stainless steel and titanium carbide ceramic is by positioning one or more intermediate connecting layers between stainless steel and titanium carbide ceramic. However, due to differing rates of heat expansion, the bond between the stainless steel and the titanium carbide ceramic is not as stable as desired.
Therefore, there is room for improvement within the art.



BRIEF DESCRIPTION OF THE DRAWINGS
Many aspects of the embodiments can be better understood with reference to the following drawings. The components in the drawings are not necessarily drawn to scale, the emphasis instead being placed upon clearly illustrating the principles of the exemplary process for joining stainless steel part and titanium carbide ceramic part, and composite article made by the process. Moreover, in the drawings like reference numerals designate corresponding parts throughout the several views. Wherever possible, the same reference numbers are used throughout the drawings to refer to the same or like elements of an embodiment.
FIG. 1 is a schematic cross-sectional view of an example of a hot press sintering device for implementing the present process.
FIG. 2 is a cross-sectional view of an exemplary embodiment of the present article made by the present process.



DETAILED DESCRIPTION
Referring to FIG. 1, an exemplary process for joining a stainless steel part and a titanium carbide ceramic part, may includes the following steps:
A titanium carbide (TiC) ceramic part 20, a titanium (Ti) foil 40, an iron (Fe) foil 50 and a stainless steel (SUS) part 30 are provided. The Ti foil 40 and the Fe foil 50 are used as a joining medium between the TiC part 20 and the SUS part 30. Each of the Ti foil 40 and the Fe foil 50 has a thickness in a range from about 0.1 millimeter (mm) to about 0.5 mm, and in this exemplary embodiment the thickness is about 0.1 mm-0.3 mm.
The TiC ceramic part 20, the SUS part 30, the Ti foil 40 and the Fe foil 50 are pretreated. The pretreatment may include the step of polishing the surfaces of The TiC ceramic part 20, the SUS part 30, the Ti foil 40 and the Fe foil 50 by silicon carbide (SiC) sandpaper to produce smooth surfaces. Then, the TiC ceramic part 20, the SUS part 30, the Ti foil 40 and the Fe foil 50 are cleaned by placing them into an organic solution to remove grease from their surfaces. The organic solution can be ethanol, and/or other organic solvents. Then, the TiC ceramic part 20, the SUS part 30, the Ti foil 40 and the Fe foil 50 are rinsed with water and dried.
A clamping mold 70 is used to hold the TiC ceramic part 20, the SUS part 30, the Ti foil 40 and the Fe foil 50. The clamping mold 70 includes a pressing board 72, a corresponding supporting board 74 and a receiving board 76. The receiving board 76 defines a cavity 762 running through the upper/bottom surface to receive the TiC ceramic part 20, the SUS part 30, the Ti foil 40 and the Fe foil 50. The pressing board 72 and the corresponding supporting board 74 extend towards the cavity 762 from opposing directions and can be moved relative to the cavity 762 by a driving system such as hydraulic pressure system. The TiC ceramic part 20, the Ti foil 40, the Fe foil 50 and the SUS part 30 are placed into the cavity 762 and clamped by the pressing board 72 and the corresponding supporting board 74. The Ti foil 40 and the Fe foil 50 are inserted between the TiC ceramic part 20 and the SUS part 30. The Ti foil 40 abuts against the TiC ceramic part 20, the Fe foil 50 abuts against the SUS part 30. The pressing board 72 and the corresponding supporting board 74 from two opposite sides, brings the surfaces of the parts to be joined into tight contact, for compressing the TiC ceramic part 20, the Ti foil 40, the Fe foil 50 and the SUS part 30.
An hot press sintering device 100 including a chamber 101 is provided. The clamping mold 70 is placed into the chamber 101. The vacuum level inside the chamber 101 is set to about 10−3 Pa to about 9×10−3 Pa. Argon (Ar) is fed into the chamber 101 to maintain the chamber 101 pressure in a range of about 0.3-0.6 MPa. The pressing board 72 and the corresponding supporting board 74 press toward each other at about 5 Mpa to firmly clamp the TiC ceramic part 20 and the SUS part 30. Then, the chamber 101 is heated at a rate of about 5-30 degrees Celsius per minute (° C./min). When the temperature of the chamber 101 reaches to about 300° C., the clamping pressure applied by the boards 72,74 steadily increases, until the temperature of the chamber 101 reaches to about 1000-1200° C., and the clamping pressure reaches to about 20-50 Mpa. The pressure and heat are maintained in their respective peak ranges for about 25-55 min, so that the Ti foil 40 and the Fe foil 50 will interact with each other, and the Ti foil 40 interacts with the TiC ceramic part 20, and the Fe foil 50 interacts with the SUS part 30. Accordingly, the TiC ceramic part 20 and the SUS part 30 are connected by the Ti foil 40 and the Fe foil 50 to form a composite article 10. The composite article 10 is removed after the chamber 101 is cooled.
Referring to FIG. 2, In the process of making the composite article 10, the Ti foil 40 and the Fe foil 50 act as intermediate layers to form a connecting layer 80 that connect the TiC ceramic part 20 and the SUS part 30. The heat expansion rate of TiC ceramic part 20 is approximately equal to that of the Ti foil 40, thus the TiC ceramic part 20 can substantially connect with the Ti foil 40. The heat expansion rate of the SUS part 30 is approximately equal to that of the Fe foil 50, thus the SUS part 30 can substantially connect to the Fe foil 50. Furthermore, the combination of the Ti foil 40 and the Fe foil 50 to form the connecting layer 80 results in a connecting layer 80 having a rate of heat expansion that gradually changes from one end to the other. Therefore, the TiC ceramic part 20 is securely connected with the SUS part 30 and more able to cope with temperature changes.
The composite article 10 manufactured by the present process includes the TiC ceramic part 20, the SUS part 30 and a multi-layered connecting layer 80 connecting the TiC ceramic part 20 to the SUS part 30. The connecting layer 80 is formed by placing the Ti foil 40 and the Fe foil 50 between the TiC ceramic part 20 and the SUS part 30, and then heating and pressing the TiC ceramic part 20 and the SUS part 30 as previously described. The various layers of the connecting layer 80 result from differing interaction between the SUS part 30, Ti foil 40, Fe foil 50, and TiC ceramic part 20. In particular, the connecting layer 80 includes:

    
    
        a) a first transition layer 81: The first transition layer 81 mainly includes compounds comprised Ti element and C element, such as TiC, Ti2C, etc. The compounds result from chemical reactions between adjacent portions of the TiC ceramic part 20 and Ti foil 40;
        b) a Ti layer 82: The Ti layer 82 results from portions of the Ti foil 40 that do not react with either the TiC ceramic part 20 or the Fe foil 50;
        c) a second transition layer 83: The second transition layer 83 is located between the Ti layer 82 and the Fe layer 84. The second transition layer 83 mainly includes chemical compounds comprising Ti element and Fe element, and Fe with Ti solid solutions. The compounds and solutions result from chemical reactions between adjacent portions to the Ti foil 40 and Fe foil 50;
        d) an Fe layer 84: The Fe layer 84 results from portions of the Fe foil 50 that do not react with either the Ti foil 40 or the SUS part 30; and
        e) a third transition layer 85: The third transition layer 85 is located between the Fe layer 84 and the SUS layer 30 and connects the Fe layer 84 and the SUS layer 30. The third transition layer 85 mainly includes Fe solid solutions, and some Chromium (Cr) solid solutions and Nickel (Ni) solid solution resulting from chemical reactions between adjacent portions of the Fe foil 50 and the SUS part 30.
    
    


The thermal expansion rate of the connecting layer 80 gradually changes from a value close to that of the TiC ceramic part 20 (in the area of 81) to a value close to that of SUS part 30 (in the area of 85). This results in a composite article 10 well suited to temperature changes due to the gradual, rather than abrupt, changes in its internal thermal expansion rates.
Furthermore, the connecting layer 80 of the composite article 10 has no crack or aperture, and has a smooth surface. The composite article 10 has high hardness, high temperature resistance, corrosion resistance and abrasion resistance, a shear strength in a range from about 50 MPa to about 80 MPa, and a tension strength in a range from about 60 MPa to about 100 MPa.
It is to be understood that even though numerous characteristics and advantages of the present embodiments have been set forth in the foregoing description, together with details of assemblies and functions of various embodiments, the disclosure is illustrative only, and changes may be made in detail, especially in matters of shape, size, and arrangement of parts within the principles of the present invention to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed.

## Claims

1. A composite article, comprising:
a TiC ceramic part,
a stainless steel part, and
a connecting layer connecting the TiC ceramic part to the stainless steel part, wherein the connecting layer is formed by placing a Ti foil and a Fe foil between the TiC ceramic part and the stainless steel part with the Ti foil abutting to the TiC ceramic part and the Fe foil abutting to the stainless steel part, then heating and pressing the TiC ceramic part, the stainless steel part, the Ti foil and the Fe foil.

2. The composite article as claimed in claim 1, wherein the connecting layer order includes a first transition layer adjacent the TiC part, a Ti layer, a second transition layer, a Fe layer, and a third transition layer adjacent the stainless steel part.

3. The composite article as claimed in claim 2, wherein the first transition layer located between the TiC ceramic part and the Ti layer mainly includes compounds comprising Ti element and C element.

4. The composite article as claimed in claim 3, wherein the compounds include TiC and Ti2C.

5. The composite article as claimed in claim 2, wherein the second transition layer located between the Ti layer and the Fe layer mainly includes compounds comprised of Ti element and Fe element, and Fe—Ti alloy solid solutions.

6. The composite article as claimed in claim 2, wherein the third transition layer located between the Fe layer and the stainless steel part mainly includes Fe solid solutions.

7. The composite article as claimed in claim 6, wherein the third transition layer further includes Cr solid solution and Ni solid solution.

8. A composite article, comprising:
a TiC ceramic part,
a stainless steel part, and
a multi-layered connecting layer connecting the TiC ceramic part to the stainless steel part, wherein:
a first layer adjacent the TiC part and comprising results of chemical reactions between TiC and Ti;
a second layer, adjacent the first layer and comprising Ti;
a third layer, adjacent the second layer and comprising results of chemical reactions between Ti and Fe;
a fourth layer, adjacent the third layer and comprising Fe; and
a last layer adjacent to the stainless steel part and comprising results of chemical reactions between Fe and stainless steel.