GB2463304A

GB2463304A - Manufacturing monocrystalline cast blades of cubic structure

Info

Publication number: GB2463304A
Application number: GB8227301A
Authority: GB
Inventors: Martial Gerard Alessandri; Jacques Leopold Emile Grammagnac; Jean-Marc Clement Francis Theret
Original assignee: Societe Nationale dEtude et de Construction de Moteurs dAviation SNECMA; SNECMA SAS
Current assignee: Safran Aircraft Engines SAS
Priority date: 1981-09-25
Filing date: 1982-09-24
Publication date: 2010-03-17
Anticipated expiration: 2002-09-24
Also published as: GB8227301D0; IT8223391A0; GB2463304B; DE3235359C1; FR2734187A1

Abstract

A method of manufacturing monocrystalline cast blades of cubic structure comprises effecting a directional solidification. A single grain crystal is selected by means of a selection device 1 at the outlet of which a single grain is to be found, of predetermined orientation and having an direction coincident with the vertical. It is arranged that the axis 12 of each portion 8 will be oriented in a direction of the selected crystal. The blades may be cast in a cluster by making a selected grain grow in a common vertical germination column 6, and the solidification front is made to progress continuously from the vertical column 6 up to the portions to be cast (18, fig 2) and along inclined branches 14 stemming from the germinating column 6.

Description

A METHOD FOR THE MANUFACTURE OF MONOCRYSTALLINE BLADES

This invention relates to a method of manufacturing in a shell mould monocrystalline cast blades or other parts of face-centred cubic structure.

In such methods the mould is fed with molten metal at its upper part, directional solidification is effected of which the front progresses vertically from the bottom to the top, a single columnar grain is selected by means of a selection device disposed in the lower part of the mould and at the outlet of which selection device a pre-determined single grain with a transverse orientation is produced. having a directionfOOlJ coincident with the vertical.

Methods for the manufacture of monocrystalline blades and parts are already known, in particular from French

Patent Specification No.1 481 366 and 2 037 187.

Furthermore, in British Application No.81.36625 filed 4th December, 1981, the Applicants proposed a method more particularly intended for the manufacture of fixed inlet guide blades of turbines.

According to. the present invention, there is provided a method of manufacturing in a shell mould, monocrystal-line cast blades with a face-centred cubic structure, the mould being supplied with molten metal at its upper part and directional solidification being effected of which the front progresses vertically from below to the top, a single columnar grain being selected by means of a selection device disposed at the lower part of the mould and at the outlet of which.a single grain is present..of.

predetermined transverse orientation and having a direc-tion [oOlj coincident with the vertical, the shells of the blades being so disposed that the axis of each por-tion will be orientated in the direction riii of the selected crystal.

An improvement in the creep properties of blades in accordance with the invention arises from the fact that it is advantageous that the structure of the monocrystalline parts should be oriented in the direction ElllJ along the principal axis of stress, that is to say, in the case where blades are cast without twist, the direction of the generating line of the blade. It is known that it is very difficult, in practice, impossible industrially, to cause a crystal to grow in this direction, but the method in accordance with the invention permits, by an ingenious arrangement, the production of monocrystalline parts orientated on the axis [111. S. -3-.

Preferably, a chicane device is used as the grain selection device, and in particular a device such as has been described in the above British Patent Application No.81.36625, that is to say, a device comprising a succession of rectilinear passages disposed in a common plane but perpendicular to one another.

The parts to be cast may be arranged as a cluster.

Preferably, the selected grain is caused to grow by the selection device as a common vertical germination column and the solidification front is caused to progress con-tinuously from the vertical column up to the parts to be cast along inclined branches stemming from the germina-tion column..

Advantageously, germination is initiated at each inclined branch, in a plurality of parts disposed parallel to the branch. More particularly, the parts are mounted in pairs at the ends of horizontal stems perpendicular to the inclined branches.

A plurality of selection devices and of vertical germina-tion columns may be arranged as a common cluster. As will be apparent from the following description, such a device enables simultaneous casting of a large number of blades (about forty).

One advantage of blades or other parts manufactured in accordance with the invention is that a micrographic examination in depth may reveal by the dentritic structure of the blade or other part examined that it has been produced in accordance with the claimed method.

The invention will now be described, by way of example, with reference to the accompanying diagrammatic drawings, in which; Figure 1 shows a front elevation of the cluster of parts to be moulded in accordance with the invention; Figure 2 is a plan view of the cluster of Figure 1; and Figure 3 shows, as a perspective view, a second arrange-ment of the cluster of test pieces' moulded in accordance with the invention.

In order to simplify the illustration, a common Figure (1 or 2), represents definitively the interface of the mould-part and the mould which are phus seen to be represented simultaneously, the same reference numerals being employed for the two corresponding parts of the one and of the other.

A grain selection device 1 is shown in Figure 1, similar to that described in British Patent Application No.81.36625 and is composed of two rectilinear passages perpendicular to one another; a vertical passage 2, a horizontal passage 3, and possibly another vertical passage 4 and another horizontal passage 5.

The selection device 1, parallel to the plane of Figure 1, discharges into a vertical column 6 for distribution of the grain.

The substantially horizontal solidification front 7, progresses from the bottom to the top in accordance with conventional techniques.

By the provision of the chicane device 1, it is ensured that one monocrystal of known orientation and defined by the said device is present in the vertical column 6; the axis 00lJ of the monocrystal is parallel to the vertical passage 2, and thus lies in the axis of the column 6, and the axis fl100j is ir the plane of the chicane.

It is also possible to develop a monocrystal of pre-determined orientation starting from a germ.

In accordance with the invention, the parts to be cast are disposed (there will be recognised here the corres-ponding form to the moulding of rotor blades 8, aerofoil 9, platform 10 and part of a root 11) in such a manner that the axis 12 of each blade will be orientated in a direction ill J of the selected crystal. The parts 8 thus form an angle = arc tg,[Twith the vertical (column 6) and an angle of 45 with the plane 13 of the chicane (Figure 2).

A rising, inclined branch 14 enables the continuous progression of the solidification front, from the vertical column 6 up to the lower part of each blade pOrtion 8.

The orientation of the branches 14 may be selected to be parallel or not to that of the blade portions 8. It is in effect the orientatIon of the part itself in a direction 11 111 which is the determining factor.

The method in accordance with the invention possesses in the sphere of metallurgy a very important advantage.

It may happen in practice that in the course of directional solidification, new grains are formed start-ing from a defect in the walls of the mould, owing to the S. -7-.

accidental presence on these walls of a grain which acts as a germinating factor.

In the proposed method, these parasitic grains of random orientation are rapidly extinguished by the growth of the main grain with directions [ 001 1 and [iO0.

The implantation of the branches 14 on the common column 6 responds to the minimal weight criterion in order to be able to dispose as many parts as possible as a common cluster. It is possible to arrange them, in the manner illustrated in Figure 1, somewhat like empty bottles on a drying rack, and distributed around the column 6 according to four directions Llll:i of the monocrystal.

In order to increase the number of parts per cluster, it is possible to mount a plurality of blades on each branch 14. Figure 2 shows the case where for each in-clined branch 14, a pair of parts 8 has been mounted at the ends of Stems 15 perpendicular to the axis 12 of the parts, which are indeed orientated in a direction E lii 1 of the crystal.

The metal supply, not shown in Figures 1 and 2, is effected at the upper part of the column 6. It is clear that it is possible to adopt any kind of arrangement other than that illustrated in Figures 1 and 2, it being understood that it is.essential to respect the orientation of each part in a direction [ ill of the monocrystal and to ensure the necessary conditions for the develop-ment in each part of the said monocrystal starting from the column 6 of the germination zone.

It is also possible to adopt an arrangement of the cluster in which a plurality of selection devices is utilised.

Thus, Figure 3 shows a group of forty parts, here cylin-drical test pieces. Five vertical columns 17 for the distribution of the grain are regularly distributed about a single metal supply arrangement 16 (only three columns are effectively illustrated) into which the upper ends of five grain selection devices 18 communicate (here, five chicanes).

At each of these five columns 17 there is a corresponding monocrystal of special orientation. For the distribu-tion of grain two vertical groups of four rough test pieces 19 and 20 (inclined branches 14 are not shown), are implanted on each column 17 at four levels the parts 19 and 20 of each col'umn being orieptated in two direc-tions [iiij of the selected monocrystal by the device 18 for the selection of the grain of the column. The outlines in a horizontal plane of the parts 19 and are perpendicular to one another, which is not, of course, readily apparent from the perspective view of Figure 3.

The supply with metal is effected from the inlet funnel 16 by inclined collectors 21 conducting the metal to the upper end of vertical supply column 22, which supplies the upper portion of each part 19, 20.

The grain selection devices 18, although they are independent one from the other, are regularly orientated with respect to the central supply 16 (for example in five planes at 720), in such a manner as to give to the cluster a symmetrical appearance about its vertical axis 23 (chain line) thus ensuring homogeneity and compactness. S.

Claims

CLAIMS1. A method of manufacturing in a shell mould, mono-crystalline cast blades with a face-centred cubic structure, the mould being supplied with molten metal at its upper part and directional solidification being effected of which the front progresses vertically from below to the top, a single columnar grain being selected by means of a selection device disposed at the lower part of the mould and at the outlet of which a single grain is present of predetermined transverse orientation and having a direction [0011 coincident with the vertical, the shells of the blades being so disposed that the axis of each portion will be orientated in the direction E11l of the selected crystal.
2. A method according to claim 1, wherein the selection device is a chicane device.
3. A method according to claim 2, wherein the chicane device is constituted by a succession of rectilinear passages disposed in a common vertical plane perpendicular to one another.
4. A method according to any one of claims 1 to 3, -11 -wherein the portions to. be moulded are arranged as a cluster.
5. A method according to claim 4, wherein the selected 5, grain is made, to grow by the selection device in a vertical single germination column and the solidification front is made to progress continuously from the vertical column up to the portions to be moulded along branches which are inclined and stemming from the germination column.
6. A method according to claim 5, wherein starting from each inclined branch, the, germination is caused to grow in a plurality of portions.
7. A method according to claim 6, wherein the said portions are mounted in pairs at the ends of horizontal stems perpendicular to the inclined branches.
8. A method according to any one of claims 5 to 7, wherein a plurality of selection devices and of vertical germination columns are disposed.in a common cluster.-12 - 9. A method of manufacturing monocrystalline cast parts in a shell mould comprising supplying the mould with molten metal, causing directional solidification from the bottom upwardly so that a single vertical grain has a direction rOOli and the individual shells of the blades are orientated with the direction [1111 10. A method of manufacturing monocrystalline cast blades or other parts substantially as hereinbefore described with respect to the accompanying drawings.11. A cast blade or other part.when made' by a method in accordance with any one of the preceding claims.Amendments to the claims have been filed as follows 1. A method of manufacturing in a shell mould, mono-crystalline cast blades with a face-centred cubic structure, the mould being supplied with. molten metal at its upper part and directional solidification being effected of which the front progresses vertically from below to the top, a single columnar grain being selected by means of a selection device disposed at the lower part of the mould and at the outlet of which a single grain is present of predetermined transverse orientation and having a direction [ooi coincident with the vertical, the shells of the blades being so disposed that the axis of each blade will be orientated in the direction rill] of the selected crystal.2. A method acrding to claim 1, wherein the selection device is a chicane device.3. A method according to claim 2, wherein the chicane device is constituted by a succession of rectilinear passages disposed in a coion vertical plane perpendicular to one another.4. A method according to any one of claims 1 to 3, ILt-wherein the portions to be tnoulded are arranged as a cluster.5. A method according to claim 4, wherein the selected grain is made to grow by the selection device in a vertical single germination column and the solidification front is made to progress continuously from the vertical column up to the portions to be moulded along branches which are inclined and stemming from the germination column.6. A method according to claim 5, wherein starting from each inclined branch, the germination is caused to grow in a plurality of portions.7. A method according to claim 6, wherein the said portions are mounted in pairs at the ends of horizontal stems perpendicular to the inclined branches.8. A method according to any one of claims 5 to 7, wherein a plurality of selection devices and of vertical germination columns are disposed in a common cluster.
9. A method of manufacturing rnonocrystalline cast elongate parts in a shell mould comprising supplying the mould with molten metal, causing directional solidi-fication from the bottom upwardly so that a single, selected, vertical grain has a direction [QO coincident with the vertical and the individual parts are orientated with their longitudinal axes in the direction of the selected crystal.
10. A method of manufacturing monocrystalline cast blades or other parts substantially as hereinbefore described with respect to the accompanying drawings.
11. A cast blade or other part when made by a method in accordance with any one of the preceding claims.