Method of joining silicon nitride to carbon steel

Details Method of joining silicon nitride to carbon steel Method of joining silicon nitride to carbon steel

1999-07-23

2001-01-09

Ryan, Patrick (Department: 1725)

Metal fusion bonding

Process

Metal to nonmetal with separate metallic filler

C228S120000, C228S203000, C228S262430, C264S647000, C264S665000

Reexamination Certificate

active

06170734

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a method of joining silicon nitride having a thin layer of active silicon metal to carbon steel, wherein the active silicon layer is formed through the thermal dissociation of silicon nitride (Si
3
N
4
) into silicon (Si) and nitrogen gas (N
2
). The active silicon layer may be directly joined to carbon steel via an induced eutectic melting reaction between Si and the iron (Fe) found in carbon steel, or via brazing of two materials such as Ag—Cu alloys.
2. Description of the Related Art
Recently, ceramic-based materials have been applied to commercial machine parts in an effort to improve efficiency and performance. The fabrication of such ceramics containing parts has generally been carried out by joining ceramic and metal, such as by joining Si
3
N
4
and carbon steel. Due to intrinsic properties associated with different materials, however, the techniques designed to join such materials remain difficult. For example, the interfacial energy between silicon nitride and Ag—Cu alloys (Y
Si3N4/AgCu
) is larger than the sum of the surface energy of silicon nitride (Y
S3N4
) and Ag—Cu alloys (Y
Ag—Cu
) alone. Therefore, these two materials do not completely wet on contact, and the joining of these two materials is difficult.
To overcome the above-described problems, Ag—Cu—Ti alloys containing silicon nitride and a highly active metal (e.g., Ti) have been used instead of Ag—Cu alloys. However, the Ag—Cu—Ti system is very expensive (about ten times higher than Ag—Cu alloys), which result in higher production costs.
Therefore, other methods have been used to join silicon nitride to carbon steel in which only the surface of silicon nitride is coated with a highly active metals (e.g., Ti, Zr) via physical method such as sputtering. This type of method activates the surface of silicon nitride such that joining can be made using Ag—Cu alloys. However, this joining method has the disadvantages of not only being very complicated but of requiring a large initial investment for sputtering equipment, which also results in increased production costs. Therefore, there is a need for a simple and economical process to join silicon nitride and carbon steel.
SUMMARY OF THE INVENTION
An object of the present invention, therefore, is to provide a simple and economical process for joining silicon nitride to carbon steel using low-priced alloys, or via direct joining two materials through a eutectic melting method. The inventors have discovered that when a thin layer of active silicon is introduced to the surface of sintered silicon nitride (Si
3
N
4
) via an in situ thermal treatment process, the silicon nitride can be easily joined to carbon steel without using a sputtering method or high-priced alloys.


REFERENCES:
patent: 4483810 (1984-11-01), Bunk et al.
patent: 4612207 (1986-09-01), Jansen
patent: 4834926 (1989-05-01), Iwasaki et al.
patent: 4954386 (1990-09-01), Mizunoya et al.
patent: 5001019 (1991-03-01), Ito et al.
patent: 5188781 (1993-02-01), Peuckert
patent: 5309874 (1994-05-01), Willermet et al.
patent: 5390843 (1995-02-01), Ito et al.
patent: 5407119 (1995-04-01), Churchill et al.
patent: 5738820 (1998-04-01), Ukegawa et al.
patent: 5904993 (1999-05-01), Takeuchi et al.
patent: 63-274679A (1988-11-01), None
patent: 4202199075A (1990-08-01), None
patent: 04343287A (1992-10-01), None

Affiliated with

Also associated with

Rating

Method of joining silicon nitride to carbon steel does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Method of joining silicon nitride to carbon steel, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method of joining silicon nitride to carbon steel will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2462443