# Patent

## Title
Composite articles made by process for joining brass part and silicon carbide ceramic part

## Abstract

A process for joining a brass part and a silicon carbide ceramics part, comprising steps of: providing parts comprising a brass part, a silicon carbide ceramics part, an aluminum foil and a nickel foil; bringing surfaces of the silicon carbide ceramics part, the aluminum foil, the nickel foil and the brass part into contact in turn; applying a joining pressure between about 10 MPa and 40 MPa to the parts; heating the parts at a rate below 50° C./min when a temperature of the parts is below about 300° C.; when the temperature of the parts is above about 300° C., heating the parts at a rate of about 80° C./min ̃200° C./min until to a joining temperature of about 550° C. to about 650° C., and maintaining the joining temperature between about 15 minutes and 40 minutes.

## Background
CROSS-REFERENCE TO RELATED APPLICATIONS
The present application is related to co-pending U.S. patent applications U.S. Ser. No. 13/166,333, entitled “PROCESS FOR JOINING BRASS PART AND SILICONE CARBIDE CERAMICS PART AND COMPOSITE ARTICLES MADE BY SAME”, by Zhang et al. This application has the same assignee as the present application and has been concurrently filed herewith. The above-identified applications are incorporated herein by reference.
BACKGROUND
1. Technical Field
The exemplary disclosure generally relates to a process for joining a metal part and a ceramic part, especially to a process for joining a brass part and an silicon carbide ceramics part, and an article made by the process.
2. Description of Related Art
It is desirable to join brass parts and silicon carbide ceramics parts. However, due to the two material having very different values for distinct physical and chemical properties, such as thermal expansion, it can be difficult to join brass and silicon carbide ceramics using traditional bonding methods such as braze welding, fusion welding, and solid diffusion bonding.
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 brass part and silicon carbide ceramics 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 spark plasma 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
The process according to the present disclosure is generally implemented by a spark plasma sintering (SPS) device as illustrated in FIG. 1.
Referring to FIGS. 1 and 2, an exemplary process for joining a brass part and an silicon carbide ceramics part may include the least the following steps.
A ceramic part 20 made of silicon carbide ceramics, a metal part 30 made of brass, and an intermediate layer 40 are provided. In this exemplary embodiment, types of the brass may comprise alpha brass, alpha-beta brass, beta brass, lead brass containing 1 wt % ̃6 wt % lead, tin brass containing 1 wt % ̃6 wt % tin, aluminum brass containing 1 wt % ̃6 wt % aluminum, manganese brass containing 1 wt % ̃6 wt % manganese, iron brass containing 1 wt % 6 wt % iron, silicone silicon brass containing 1 wt % ̃6 wt % silicone silicon, or nickel brass containing 1 wt % ̃6 wt % nickel. The intermediate layer 40 connects together the surfaces of the metal part 30 and the ceramic part 20. The intermediate layer 40 may include an aluminum foil 41 and a nickel foil 43 stacked on the aluminum foil 41. The aluminum foil 41 is adjacent to the ceramic part 20 and the nickel foil 43 is adjacent the metal part 30. Each of the aluminum foil 41 and the nickel foil 43 has a thickness of about 0.1 mm ̃0.5 mm, such as about 0.1 mm, 0.15 mm, 0.25 mm, 0.35 mm, 0.4 mm, or 0.5 mm . . . .
The metal part 30, ceramic part 20, and intermediate layer 40 are pretreated. The pretreatment may include polishing the surfaces of the metal part 30, ceramic part 20, and intermediate layer 40, by a 600 grit ̃1000 grit abrasive paper. Then, the metal part 30, ceramic part 20, and intermediate layer 40 may be activated through a cleaning process with a solution containing hydrochloric acid or sulphuric acid. Then, the metal part 30, ceramic part 20, and intermediate layer 40 are rinsed with water and dried.
A mold 50 made of electroconductive material, such as graphite, is provided as shown in FIG. 1. The mold 50 includes an upper pressing head 51, a lower pressing head 52, and a middle part 53. The middle part 53 defines a cavity (no shown) for accommodating the parts to be joined.
Subsequently, the metal part 30, ceramic part 20, and intermediate layer 40 are placed into the mold 50 with the intermediate layer 40 inserted between the metal part 30 and the ceramic part 20, the aluminum foil 41 contacts the ceramic part 20 and the nickel foil 43, and the nickel foil 43 contacts the metal part 30 and the aluminum foil 41. The upper pressing head 51 and the lower pressing head 52 from two opposite sides compress the metal part 30, ceramic part 20, and intermediate layer 40 together.
A SPS device 10 is provided. The SPS device 10 includes a pressure system 11 for providing pressure to the parts to be joined, a sintering chamber 13, and a DC pulse power 14 for providing pulse current to the parts and heating up the parts. The DC pulse power 14 includes a positive electrode 16 and a negative electrode 17. The pulse-width ratio of the DC pulse power 14 is 6:1, and the maximum amps of the DC pulse power 14 is 8000 A.
The mold 50 is placed in the sintering chamber 13. The upper pressing head 51 and the lower pressing head 52 are electrically connected to the positive electrode 16 and negative electrode 17 of the DC pulse power 14. The sintering chamber 13 is evacuated to a vacuum level between about 6 Pa and about 10 Pa. A pressure between about 10 MPa and 40 MPa, such as 10 MPa, 15 MPa, 20 MPa, 30 MPa, 35 MPa or 40 MPa, is then applied to the parts through the upper pressing head 51 and the lower pressing head 52. While the g pressure is applied, a pulse electric current between about 1000 A and 8000 A with a pulse-width ratio of 6:1 is simultaneously applied to the parts, heating the parts at a rate less than 50 degrees Celsius per minute (° C./min) when the temperature of the parts are less than about 300° C., and heating the parts at a rate of about 80° C./min ̃° C./min 200° C./min when the temperature of the parts are above about 300° C. The temperature of the parts are maintained at about 550° C. to about 650° C., for about 15 minutes and 40 minutes, such as 15 minutes, 20 minutes 30 minutes or 40 minutes. Under the above mentioned conditions, particles of the metal part 30, ceramic part 20, and intermediate layer 40 will react and fuse with each other to form a joining part 80 (shown in FIG. 2) having multiple between the metal part 30 and the ceramic part 20. Thereby, the metal part 30 and the ceramic part 20 are joined via the intermediate layer 40, forming a composite article 100.
Once the composite article 100 is cooled down, the composite article 100 can be removed.
Owing to the present process, a permanent joining part 80 of great strength is obtained. The process requires a short hold time and a low vacuum level of the sintering chamber 13, thus significantly saves time and energy. The aluminum foil 41 has a low melting point, so the aluminum foil 41 can be melted when the parts are heated, causing the aluminum foil 41 and the ceramics part 20 be fused together. Additionally, coefficients of thermal expansion of the ceramic part 20, aluminum foil 41, nickel foil 43, metal part 30 are gradually increased, i.e., a coefficient of thermal expansion of the intermediate layer 40 is between the coefficient of thermal expansion of the ceramics part 20 and the coefficient of thermal expansion of the metal part 30 and gradually changes from a value close to that of the ceramic part 20 in the area of the bond of the ceramic part 20 and the joint part 80 to a value close to that of the metal part 30 in the area of the bond of the joint part 80 with the metal part 30. Thus, thermal stress between the ceramics part 20 and metal part 30 can be reduced by the intermediate layer 40 thereby improving the binding force between the ceramics part 20 and metal part 30 so the ceramics part 20 can be firmly joined with the metal part 30.
FIG. 2 shows a composite article 100 manufactured by the present process. The composite article 100 includes the metal part 30, the ceramic part 20, and a multi-layered joining part 80 joining the metal part 30 and the ceramic part 20. The various layers of the joining layer 80 result from differing interaction between the metal part 30, aluminum layer 82, nickel layer 84, and ceramic part 20. In particular, the joining layer 80 includes:
a) a first transition layer 81: The first transition layer 81 is located between the ceramics layer 20 and the aluminum layer 82. The first transition layer 81 mainly includes compounds composited aluminum element and carbon element, such as aluminum carbide, and compounds composited aluminum element and silicon element, such as aluminum silicide, etc. This chemical results result from chemical reactions between adjacent portions of the ceramics layer 20 and aluminum layer 82;
b) an aluminum layer 82: The aluminum layer 82 results from portions of the aluminum layer 82 that do not react with either the ceramics layer 20 or the nickel layer 84;
c) a second transition layer 83: The second transition layer 83 is located between the nickel layer 84 and the aluminum layer 82. The second transition layer 83 mainly includes chemical compounds comprising nickel element and aluminum element, and of nickel with aluminum solid solutions. The chemical results result from chemical reactions between adjacent portions to the aluminum layer 82 and the nickel layer 84;
d) a nickel layer 84: The nickel layer 84 results from portions of the nickel layer 84 that do not react with either the aluminum layer 82 or the ceramic part 20;
e) a third transition layer 85: The third transition layer 85 is located between the nickel layer 84 and the metal part 30. The third transition layer 85 mainly includes nickel with copper solid solutions, and chemical compounds comprising nickel element and copper element. The chemical results result from chemical reactions between adjacent portions to the nickel layer 84 and the metal part 30.
The thermal expansion rate of the joining layer 80 gradually changes from a value close to that of the ceramic part 20 (in the area of 81) to a value close to that of the metal part 30 (in the area of 85). This results in a composite article well suited to temperature changes due to the gradual, rather than abrupt, changes in its internal thermal expansion rates.
Furthermore, the joining part 80 of the composite article 100 has no crack or aperture, and has a smooth surface. The metal/ceramic interface of the composite article 100 has a shear strength between about 20 MPa and 40 MPa, and a tensile strength between about 30 MPa and 60 MPa.
It is to be understood, however, that even through numerous characteristics and advantages of the exemplary disclosure have been set forth in the foregoing description, together with details of the system and function of the disclosure, 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 disclosure 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 metal part made of brass;
a ceramic part made of silicon carbide ceramic; and
a joining part, the joining part including a first transition layer, an aluminum layer, a second transition layer, a nickel layer and a third transition layer; the first transition layer located between the ceramic part and the aluminum layer, the first transition layer substantially comprised of compounds of aluminum and carbon, and compounds of aluminum and silicon; the second transition layer located between the nickel layer and the aluminum layer, the second transition layer substantially comprised of intermetallic compounds of nickel and aluminum, and solid solutions of nickel and aluminum; the third transition layer located between the nickel layer and the metal part, the third transition layer substantially comprised of solid solutions of nickel and copper, and intermetallic compounds of nickel and copper.

2. The composite article as claimed in claim 1, wherein the metal/ceramic interface of the composite article has a shear strength between 20 MPa and 40 MPa.

3. The composite article as claimed in claim 1, wherein the metal/ceramic interface of the composite article has a tensile strength between about 30 MPa and 60 MPa.