Composite articles made by process for joining stainless steel part and zirconia ceramic part

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

CROSS-REFERENCE TO RELATED APPLICATIONS

The disclosures of the three listed applications are incorporated by reference in this instant application. All listed applications have the same assignee.

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 zirconia ceramic part, and a composite article made by the process.

2. Description of the Related Art

It is desirable to join stainless steel parts and zirconia ceramic parts. A typical process for joining stainless steel and zirconia ceramic is by positioning physically separate copper foil or molybdenum foil as intermediate layer between stainless steel and zirconia ceramic. However, the foil retains its separate nature through manufacturing and in the final product and does not chemically interact with the stainless steel or zirconia ceramic. Furthermore, in case of using physically separate copper foil, due to great difference between the coefficients of heat expansion of the zirconia ceramic and the copper foil, the ceramic/copper interface has large thermal stress, thus, the bond between the stainless steel and the zirconia ceramic via copper foil is not as stable as desired. In case of using physically separate molybdenum foil, due to having a relatively low reaction activity, it is difficult for zirconia ceramic and molybdenum foil to inter-diffuse into each other, enhancing the difficulty of bonding the various separate intermediate layers.

Therefore, there is room for improvement within the art.

DETAILED DESCRIPTION

Referring toFIG. 1, an exemplary process for joining a stainless steel part and a zirconia ceramic part, may includes the following steps:

A zirconia (ZrO) ceramic part20, a molybdenum (Mo) foil40, an nickel (Ni) foil50and a stainless steel (SUS) part30are provided. The Mo foil40and the Ni foil50are used as a joining medium between the ZrO ceramic part20and the SUS part30. The Mo foil40has a thickness in a range from about 0.1 millimeter (mm) to about 0.3 mm, and the Ni foil50has a thickness in a range from about 0.2 mm to about 0.4 mm.

The ZrO ceramic part20, the SUS part30, the Mo foil40and the Ni foil50are pretreated. The pretreatment may include the step of polishing the surfaces of The ZrO ceramic part20, the SUS part30, the Mo foil40and the Ni foil50by silicon carbide (SiC) sandpaper to produce smooth surfaces. Then, the ZrO ceramic part20, the SUS part30, the Mo foil40and the Ni foil50are 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 ZrO ceramic part20, the SUS part30, the Mo foil40and the Ni foil50are rinsed with water and dried.

A nickel (Ni) coating60on the surface of the ceramic part20is further provided. The Ni coating60may be made by vacuum coating such as magnetron sputtering or chemical coating. The Ni coating60has a preferred thickness of about 4 μm˜10 μm.

A clamping mold70is used to hold the ZrO ceramic part20, the SUS part30, the Mo foil40and the Ni foil50. The clamping mold70includes a pressing board72, a corresponding supporting board74and a receiving board76. The receiving board76defines a cavity762running through the upper/bottom surface to receive the ZrO ceramic part20, the SUS part30, the Mo foil40and the Ni foil50. The pressing board72and the corresponding supporting board74extend towards the cavity762from opposing directions and can be moved relative to the cavity762by a driving system such as hydraulic pressure system. The ZrO ceramic part20, the Mo foil40, the Ni foil50and the SUS part30are placed into the cavity762and clamped by the pressing board72and the corresponding supporting board74. The Mo foil40and the Ni foil50are inserted between the ZrO ceramic part20and the SUS part30. The Mo foil40abuts against the Ni coating60on the ZrO ceramic part20, the Ni foil50abuts against the SUS part30. The pressing board72and the corresponding supporting board74from two opposite sides, brings the surfaces of the parts to be joined into tight contact, for compressing the ZrO ceramic part20, the Mo foil40, the Ni foil50and the SUS part30.

A hot press sintering device100including a chamber101is provided. The clamping mold70is placed into the chamber101. The vacuum level inside the chamber101is set to about 10−3Pa to about 9×10−3Pa. Argon (Ar) is fed into the chamber101to maintain the chamber101pressure in a range of about 0.3 MPa-0.6 MPa. The pressing board72and the corresponding supporting board74press toward each other at about 10 Mpa to firmly clamp the ZrO ceramic part20and the SUS part30. Then, the chamber101is heated at a rate of about 10 degrees Celsius per minute (° C./min)-50° C./min. When the temperature of the chamber101reaches to about 300° C., the clamping pressure applied by the boards72,74steadily increases, until the temperature of the chamber101reaches to about 800° C.-1100° C., and the clamping pressure reaches to about 0.3 MPa-0.6 MPa. The pressure and heat are maintained in their respective peak ranges for about 35 min-75 min, so that the Mo foil40and the Ni foil50will chemically interact with each other, and the Mo foil40chemically interacts with the ZrO ceramic part20, and the Ni foil50chemically interacts with the SUS part30. Accordingly, the ZrO ceramic part20and the SUS part30are connected by the Mo foil40and the Ni foil50to form a composite article10. The composite article10is removed after the chamber101is cooled.

Referring toFIG. 2, in the process of making the composite article10, the Mo foil40and the Ni foil50act as intermediate layers to form a connecting layer80that connects the ZrO ceramic part20and the SUS part30. The heat expansion rate of ZrO ceramic part20is approximately equal to that of the Mo foil40, thus the ZrO ceramic part20can substantially connect with the Mo foil40. The heat expansion rate of the SUS part30is approximately equal to that of the Ni foil50, thus the SUS part30can substantially connect to the Ni foil50. Furthermore, the combination of the Mo foil40and the Ni foil50to form the connecting layer80results in a connecting layer80having a rate of heat expansion that gradually changes from one end to the other. Therefore, the ZrO ceramic part20is securely connected with the SUS part30and more able to cope with temperature changes.

The composite article10manufactured by the present process includes the ZrO ceramic part20covered by the Ni coating60, the SUS part30and a multi-layered connecting layer80connecting the ZrO ceramic part20to the SUS part30. The connecting layer80is formed by placing the Mo foil40and the Ni foil50between the ZrO ceramic part20and the SUS part30, and then heating and pressing the ZrO ceramic part20and the SUS part30as previously described. The various layers of the connecting layer80result from differing chemical interactions between the SUS part30, Mo foil40, Ni foil50, and ZrO ceramic part20. In particular, the connecting layer80includes:

a) a first transition layer81: The first transition layer81mainly includes intermetallic compounds comprising Ni element and Mo element, intermetallic compounds comprising Zr element and Ni element, Ni with Mo solid solutions, and Zr with Ni solid solutions. The compounds result from chemical reactions between adjacent portions of the ZrO ceramic part20and Mo foil40;

b) a Mo layer82: The Mo layer82results from portions of the Mo foil40that do not chemically react with either the ZrO ceramic part20or the Ni foil50;

c) a second transition layer83: The second transition layer83is located between the Mo layer82and the Ni layer84. The second transition layer83mainly includes intermetallic compounds comprising Mo element and Ni element, and Mo with Ni solid solutions. The compounds and solutions result from chemical reactions between adjacent portions to the Mo foil40and Ni foil50;

d) an Ni layer84: The Ni layer84results from portions of the Ni foil50that do not chemically react with either the Mo foil40or the SUS part30; and

e) a third transition layer85: The third transition layer85is located between the Ni layer84and the SUS layer30and connects the Ni layer84and the SUS layer30. The third transition layer85mainly includes intermetallic compounds comprising Fe element and Ni element, and Fe with Ni solid solutions. The compounds and solutions result from chemical reactions between adjacent portions to the Ni foil50and SUS layer30.

The thermal expansion rate of the connecting layer80gradually changes from a value close to that of the ZrO ceramic part20(in the area of 81) to a value close to that of SUS part30(in the area of 85). This results in a composite article10well suited to temperature changes due to the gradual, rather than abrupt, changes in its internal thermal expansion rates.

Furthermore, the connecting layer80of the composite article10has no cracks or apertures, and has a smooth surface. The composite article10has high hardness, high temperature resistance, corrosion resistance and abrasion resistance, shear strength in a range from about 50 MPa to about 80 MPa, and tension strength in a range from about 60 MPa to about 100 MPa.