Method for high vacuum casting

Claim 1

A method of casting a superalloy ingot which is a nickel- or cobalt-based alloy containing at least about 50% nickel or cobalt, respectively, and between about 10% and 20% chromium, from a stick at high vacuum comprising: melting the stick using one or more electron beams to produce a substantially linear series of fully molten drops, each drop of which falls on the upper surface on an ingot being formed to cover a portion thereof which is substantially less than the ingot's total upper surface, controlling the electron beam heating rate and the distance of the stick above the upper surface of the ingot such that each drop forms a film-like spatter having a surface dimension of between about 3.8 and 7.6 centimeters and wherein the thickness of the spatter is between about 0.04 mm and 0.08 mm, providing relative movement between the stick and the ingot being formed at a rate which is high enough so that the successive drops will impinge upon different portions of the ingot's upper surface to lay down a series of substantially level close-packed arrays of overlapping spatters, each array covering the upper surface of the ingot substantially uniformly, but which rate of relative movement is low enough to prevent a substantial flow of the spatters on the surface of the ingot, and maintaining the drip rate such that the impact region on the ingot's upper surface is at or below the solidus temperature of the superalloy and above a temperature at which metallurgical bonding with the successive impinging drops can occur and such that the average rate of vertical buildup of the ingot is less than or equal to about one centimeter per minute and the drop pattern is sufficiently uniform to avoid successive drop impingements in the same area at intervals less than about three seconds to thereby avoid localized pooling.

Claim 2

A method of casting a superalloy ingot which is a nickel- or cobalt-based alloy containing at least about 50% nickel or cobalt, respectively, and between about 10% and 20% chromium, from a stick at high vacuum comprising: melting the stick using one or more electron beams to produce a substantially linear series of fully molten drops, each drop of which falls on the upper surface on an ingot being formed to cover a portion thereof which is substantially less than the ingot's total upper surface, controlling the electron beam heating rate and the distance of the stick above the upper surface of the ingot such that each drop forms a film-like spatter having a surface dimension of between about 3.8 and 7.6 centimeters and wherein the thickness of the spatter is between about 0.04 mm and 0.08 mm, providing relative movement between the stick and the ingot being formed at a rate which is high enough so that the successive drops will impinge upon different portions of the ingot's upper surface to lay down a series of substantially level close-packed arrays of overlapping spatters, each array covering the upper surface of the ingot substantially uniformly, but which rate of relative movement is low enough to prevent a substantial flow of the spatters on the surface of the ingot, and maintaining the drip rate such that the impact region on the ingot's upper surface is at or below the solidus temperature of the superalloy and above a temperature at which metallurgical bonding with the successive impinging drops can occur and such that the average rate of vertical buildup of the ingot is less than or equal to about one centimeter per minute and the drop pattern is sufficiently uniform to avoid successive drop impingements in the same area at intervals less than about three seconds to thereby avoid localized pooling.