US3054693A - Shaft bearing surface - Google Patents

Description

Patented Sept. 18, 1962 ice This invention relates to a method of applying a metallic bearing surface to the surface of a member made of a different metal or alloy.

A simplified flow diagram of the method of the present invention is as follows:

Shaft of nickel base alloy Masking of areas except where bearing surface required Spraying with bearing metal Immersion into bath of boric cryolite at high temperature Maintaining in bath until temperature of shaft reaches that of bath Removal from bath According to the invention a method of applying, to a first metallic surface, a bearing surface of a second metal or alloy, comprises spraying the second metal or alloy on the first surface and then immersing the sprayed area into a fusing bath. The bath can be, for example, molten boric cryolite, or barium chloride.

Preferably the bath is raised to a suitable temperature, say 1060 to 1070 C., prior to insertion of the sprayed area into the bath, and the sprayed area is retained in the bath until the metal member has reached the temperature of the bath.

This process causes diffusion of the second metal or alloy to a limited extent into the first metallic surface. For example, in the use of Metco 16C alloy as a bearing surface metal for application to Nimonic 80A, the Metco 16C diffuses to a depth of about five thousandths of an inch into the Nimonic alloy.

The Metco 16C is then firmly keyed to the Nimonic 80A and a full diffusion bond is established.

One particular application of the invention is to the production of journal shafts for supporting thrust reversers of gas turbine engines. These shafts have to be made of an alloy which will withstand the high temperatures and rapid changes of temperature involved in gas turbine reverser operation. Nimonic 80A is one such metal which is suitable, but this metal is not suitable itself for use :as a bearing surface. As understood in the art, Nimonic 80A is an alloy having a composition of 18% to 21% chromium, 5.0% maximum iron, 1.8% to 2.7% titanium, 0.5% to 1.8% aluminum, 2.0% maximum cobalt, 1.0% maximum manganese, 1.0% maximum silicon, 0.1% maximum carbon and a balance of nickel.

Metco 16C, which is an alloy comprising nickel as its main constituent with about 16% of chromium and additions of boron, silicon, copper and iron is a suitable alloy for forming a bearing surface. As understood in the art Metco 16C is an alloy having a composition of 16.0% chromium, 4.0% boron, 4.0% silicon, 3.0% copper, 2.5% iron, 3.0% molybdenum, 0.5% carbon and a balance of nickel.

The difficulty lies in bonding the Metco 16C to the Nimonic A and it is the purpose of this invention to overcome the difliculty.

The method used in practice is to mask the portion of the Nimonic alloy shaft which is not to be sprayed and prepare it by blasting with sand or with steel shot the area which is to be sprayed. The bearing area is then sprayed With the bearing metal. A bath of boric cryolite is then raised to a temperature of 1060 to 1070 C., the shaft is inserted into the bath so that the sprayed part is entirely immersed and it is left there until the temperature of the shaft reaches that of the bath. This usually takes about 10 to 20 minutes, by which time the Metco 16C is diffused into the Nimonic alloy to a sufiicient depth to make a full diffusion bond.

Other heat resistant materials which can be used in place of Metco 16C in this particular application include Stellite and like materials. As understood in the art Stellite is an alloy having a composition of 40% to 60% cobalt, 20% to 35% chromium, 0 to 25% tungsten, .75 to 2.5% carbon and O to 3% silicon.

The preparation of the boric cryolite flux bath for a different purpose is described in our British Patent 698,425 and the bath may be prepared in the same way for this application.

What I claim is:

1. -A method of applying a hard metal bearing surface to a shaft made of nickel base high temperature alloy comprising the steps of: masking the area of the shaft except Where the hard metal bearing surface is to be applied, sand blasting the unmasked area, spraying the unmasked area with the hard bearing metal, entirely im mersing the sprayed part of the shaft into a bath of boric cryolite at a high temperature, maintaining the immersed portion in the bath until the temperature of the shaft reaches about that of the bath, whereby the hard bearing metal is diffused into the nickel base high temperature alloy of the shaft to a sufficient depth to make a full diffusion bond, and then removing the shaft from the bath.

2. A method in accordance with claim 1 wherein the temperature of the bath is elevated in the order of 1060 C. to 1070" C.

3. A method in accordance with claim 11 wherein the hard bearing metal is a hard alloy comprising nickel as its main constituent with about 16% of chromium and additions of boron, silicon, copper and iron.

References Cited in the file of this patent UNITED STATES PATENTS 2,315,725 Moller Apr. 6, 1943 2,588,421 Shepard Mar. 11, 1952 2,885,304 Thomson et a1. May 5, 1959 2,889,238 Long et al. June 2, 1959 2,955,958 Brown Oct. 11, 1960

Claims (1)

1. A METHOD OF APPLYING A HARD METAL BEARING SURFACE TO A SHAFT MADE OF NICKEL BASE HIGH TEMPERATURE ALLOY COMPRISING THE STEPS OF: MASKING THE AREA OF THE SHAFT EXCEPT WHERE THE HARD METAL BEARING SURFACE IS TO BE APPLIED, SAND BLASTING THE UNMASKED AREA, SPRAYING THE UNMASKED AREA WITH THE HARD BEARING METAL, ENTIRELY IMMERSING THE SPRAYED PART OF THE SHAFT INTO A BATH OF BORIC CRYOLITE AT A HIGH TEMPERATURE, MAINTAINING THE IMMERSED PORTION IN THE BATH UNTIL THE TEMPERATURE OF THE SHAFT REACHES ABOUT THAT OF THE BATH, WHEREBY THE HARD BEARING METAL IS DIFFUSED INTO THE NICKEL BASE HIGH TEMPERATURE ALLOY OF THE SHAFT TO A SUFFICIENT DEPTH TO MAKE A FULL DIFFUSION BOND, AND THEN REMOVING THE SHAFT FROM THE BATH