FR2663872A1 - MANUFACTURE OF TUBES USING A REUSABLE CHUCK. - Google Patents

Abstract

The present invention relates to a method of manufacturing a multiplicity of ring structures having substantially the same internal diameter. A first step in the method consists in providing a mandrel (10) with a relatively high coefficient of thermal expansion and the deposition of a non-reactive oxide layer (14) on the surface of the mandrel. After the oxide deposit, a layer of metal (22) is deposited to form a ring structure on the mandrel. The coefficient of thermal expansion of the metal constituting the mandrel and that of the deposited metal are sufficiently distinct for spontaneous separation of the deposited ring structure to occur when the mandrel and the deposited layer are cooled to room temperature. Before the deposition of a new layer of metal, the oxide layer is restored.

Description

MANUFACTURE OF TUBES USING A REUSABLE CHUCK

  The present invention relates generally to the manufacture of tubes by plasma spraying techniques. More particularly, it relates to the formation by plasma spraying of objects of general tubular shape using a reusable mandrel.

  It is known that spray technology

  Rization under plasma can be used for the formation of objects of various configurations. Several patents concern the

  process for forming objects by plasma spraying

  reading radio frequency plasmas (RF) oahe plasma medium.

  The preparation of sheets based on titanium alloy and similar objects and on reinforced structures in which silicon carbide fibers are housed in a titanium based alloy is described in American patents 4775547, 4782884, 4786566, 4805294 , 4805833 and 4838337, assigned to the assignee of this application The texts of these patents will be considered here

O Eit M oonnus.

  The preparation of comtposites as described in these patents is the subject of in-depth studies since the composites have very good mechanical resistance properties

  One of the properties which is parti-

  Culièraemnt desirable lies in the very high qualities of resistance to rupture oenférés structures with very

  good breaking strength properties of fibers or fila-

  silicon carbide elements The tensile strength properties of structures are linked to the mixing rule According to

  This rule, the proportion of a property, such as the pro-

  fracture toughness, which is assigned to the filaments, and not to the matrix, is determined by the percentage

  volume of filaments present in the structure and by the resistance

  breaking strength of the filament itself Similarly, the proportion of the same breaking strength property that is assigned to the matrix is determined by the percentage

  volume of the matrix present in the structure and resistance

  tance at break of the matrix itself.

  Prior to the development of the processes described in the aforementioned patents, such structures were prepared by sandwiching the reinforcing filaments between

  titanium-based alloy sheets and pressing the stack

  of alternate alloy layers and reinforcing filaments

  until a composite structure is formed Any-

  times, this prior art method has been found to be less than satisfactory when attempts have been made to form ring structures in which the filaments serve as

  internal reinforcement for the complete ring.

  The structures described in the aforementioned patents and the processes by which they are formed, have brought significant progress over prior techniques of matrix sandwich and reinforcing filaments

by compression.

  It was later discovered that, while the

  structures prepared as described in the above patents

  above referenced have properties that exhibit great

  improvement over previous St res, the resis-

  very high ultimate tensile strength which can be achieved with these structures does not reach the theoretically possible values Tests carried out on corposites formed according to the methods taught in the above patents have shown that, although the values of the failure modalities are generally in good agreement with the forecasts of the mixing rule, the ultimate breaking strength is usually much lower

  to oe which is predicted by the underlying properties of oomnpo-

individual health of the composite.

  Urn structures that turned out to be special-

  mentally desirable according to the technology of the aforementioned patents is an annular product comprising a metallic material and provided with a reinforcement with silicon carbide filaments extending several times around the complete ring These ring structures have very good resistance properties at break in relation to their weight, in particular when compared to totally metallic structures. However, it has proved difficult, in particular because of the too high temaperatures which must be used for the formation of these products, to obtain a ring structure which is dimensionally very precise in terms of its internal dimensions Ces

  structures must be careful in terms of their dimensions

  so that they can be used very efficiently.

  cement in a final application provided that the structures are often used as elements of a more complex structure and for this purpose are nested on one or more

  elements of a circular assembly to serve as a reinforcing ring

  cement. One of the structures formed comprises a reinforcing filament wound several times and, in several layers around the ciroonferene, there is a reinforced ring structure. The reinforced ring can be used, for example, as a reinforcement ring for compressor blades. a jet engine compressor disc To maintain the blades in a jet engine compressor stage, a large number of layers of reinforcing filaments is required It has been found to be very difficult to continue to add more and more layers of filamentary reinforcement to a ring structure due to the difference in coefficient of thermal expansion and for other reasons One way of solving this problem has been to form several concentric rings which

  are then joined together to provide a structure

  reinforced ring structure comprising more than 100 layers of reinforcement

  cement Such ring structures can have fairly large diameters of the order of thirty centimeters or several thirty centimeters (several feet) and must nevertheless be nested to each other with very close tolerances of only a few thousandths of

  centimeters (a few thousandths of an inch).

  To form a set of reinforced ring structures, it is desirable to provide a set of standard internal diameter for the rings to be assembled so that some standardization of the dimensions of the ring structure can be used to simplify the manufacturing processes and to save some money in the manufacturing of the ring For example, if an overall structure must have an internal diameter of around 30 centimeters (one foot), several rings with different starting diameters can be used to form an assembly of reinforced structures each of which has a thickness of for example 5 mm (0.2 inch) For example, if an overall ring structure must have an internal diameter of 30 cm and a total of more than 100 layers, it may be desirable to fabricate the structure using 5

  nested rings each comprising 20 individual layers.

  Since each layer has a thickness of approximately 0.22 to 0.25 mm (0.009 to 0.010 inch), each circle will have a thickness of approximately mm (0.2 inch). Thus, the initial ring structures to be nested will have internal diameters of 30.5, 31.5, 32.5, 33.5 and 34.5 cm (12, 12.4, 12, 8, 13.2 and 13.6 inches) Each of these rings can be used as a starting ring for the deposition of the reinforcing and matrix material in layers having a

total thickness of about 5 mm.

  Accordingly, there is a need for a convenient and economical process for producing sets of starting rings having

  tightly reproducible internal diameters.

  Thus, an object of the present invention is to provide

  a process by which a ring structure deposited by spraying

  Plasma production can be produced economically and reliably. Another object of the present invention is to provide a process which allows the production of ring structures deposited by plasma spraying having diameters

well-defined internal.

  Another object of the present invention is to provide a process which by itself leads to the economical and reliable production of ring structures which have internal dimensions

defined in a reproducible manner.

  Other objects and advantages of the present invention will be clear on the one hand to those skilled in the art and on the other hand

  underlined in the description below.

  In one of their most general aspects, the ob-

  jets of the present invention can be achieved by providing

  a mandrel having a coefficient of relative thermal expansion-

  high and with slightly smaller external dimensions

  res to the internal dimensions of the ring structure to be formed.

  The mandrel is heated in a plasma torch and is then subjected to a plasma spraying of a surface layer of protective oxide such as an aluminum oxide egg. After the deposit of the protective oxide on the surface of the chuck, one

  spray deposition of a matrix crystal having a coeffi-

  cient of thermal expansion noticeably lower than that of the mandrel is applied to the surface of the mandrel coated with oxide The mandrel coated with oxide is then left to cool and the tube deposited with matrix metal to cool to room temperature During cooling, the mandrel is contracts and moves away from the tube

  matrix metal due to the relatively large difference

  aunt of coefficient of thermal expansion of their respective materials The surface of the mandrel coated with oxide separates from the ring so that the ring can be removed from the mandrel It will be noted that the separation between the ring and the mandrel occurs in the oxide layer so that the initial oxide layer must be partially reformed before a second matrix layer is deposited After removal of the matrix metal ring, the mandrel is again heated to a temperature of which a spray deposition under plasmna of a protective oxide coating and a layer of matrix metal can be formed on the mandrel The second ring of matrix metal is formed on the oxide coated mandrel and this ring and the mankdrin it surrounds are allowed to cool to room temperature to cause separation between the ring and the surface

coated with oxide.

  The process of depositing ring structures on the

  oxide coated surface is repeated from which it results that a plu-

  lity of ring structures obtained by plasma spraying having basically the same internal diameter is

  produced reliably and economically.

  By providing a set of mandrels of different diameters, sets of die mnetal rings having

  reproducible diameters can be manufactured.

  The detailed description of the invention which follows is

  will understand well with reference to the accompanying drawings, in which: FIG. 1 is a partially schematic perspective representation of a mandrel to which a surface coating of a protective oxide has been applied; Figure 2 is a partially schematic perspective representation of the deposition on the oxide-coated mandrel of Figure 1 of a matrix metal by plasma spraying; and Figure 3 is a partially schematic perspective representation of the oxide-coated mandrel of Figure 1 during removal of the ring structure deposited by plasma spraying after the structures have been cooled. It is known that deposition by RF plasma spraying of a metallic material of titanium-based material on a substrate can be used to form a sheet of the matrix material. Such a process is described in US Patent N 4,838,337 Many other structures have been formed by plasma spraying of a metal on a substrate and there is an abundant patent and technical literature on these methods. However, when the substrate is a mandrel, the conventional method of removing the mandrel consists either to eliminate the mandrel by machining inside the deposit by plasma spraying or else to chemically dissolve the mandrel

  inside the plasma spray depot.

  In the present process, the mandrel and the deposited ring structure spontaneously and automatically separate from each other so that the ring structure can be removed from the mandrel on which it is deposited without using chemical dissolving agents. or to machining or other

metal working techniques.

  The technique by which a plurality is obtained

  rings deposited by spraying under plasma having essential-

  one the same internal dimensions depends on a combination of actions One of these actions consists of coating the surface of the mandrel with a surface coating of oxide intended to serve as a release agent for the separation of a material deposited by plasma spraying of the substrate on which it

is filed.

  The second action on which the process depends resides in the provision of a mandxirin having a coefficient of thermal expansion sufficiently large compared to that of the matrix material which is deposited by spraying under plasma on this mandrel so that the mandrel tends to become contract away

  of the internal surface of the ring structure deposited by spraying

  risation under plasma which is formed there It is the combination of the elements of the process of the present application which makes possible the repeated manufacture of ring structures having essentially the same internal diameter from a single structure of

starting chuck.

  Some of the advantages of the present invention will be better understood when considered in relation to a manufacturing process with which the present invention can beforehand

carefully be used.

  The illustration is given above of the need to obtain

  tion of a set of rings which can be nested one inside the other concentrically to produce a single ring comprising a relatively high number of reinforcing layers by filaments greater than a hundred such layers. For this purpose, a set of five onerntric rings each having about twenty layers of reinforcing filaments is presented by way of example in the description of the background of the invention Each of the five rings has a distinct internal diameter and differs by approximately 1 cm from the diameter internal of

  the adjacent ring, more or less.

  What is desired to provide such a set of filament-reinforced rings which is made possible by the present invention is the production of starting matrix structures which have initial diameters which are reliably reproducible within a tolerance range narrow with respect to a predetermined initial diametral dimension In other words, if it is sought to obtain a ring structure having an internal diameter of 30 centimeters, the method according to the present invention provides for the production of a ring structure having a diameter internal 30.5 ncm (12 inch) with a very narrow tolerance range And the same manufacturing possibility exists for rings of 31.5, 32.5, 33.5 and 34.5 ncm (12.4,

12.8, 13.2 and 13.6 inches).

  The production of a single ring structure of this type is described below in relation to the Craroe figures.

  shows Figure 1, a mandrel 10 has a slight outer diameter

  rement less than the diameter of the ring to be manufactured The mandrel 10 is preferably thick or full wall as shown in Figure 1 This wall thickness is preferable to avoid distortion of the shape of the mandrel to a non-circular shape due to the sequence of heating and

  cooling when the chuck is used many times.

  The mandrel first receives a plasma spray of a

  protective oxide layer using a conventional plasma cannon

  12 and using an oxide powder such as aluminum oxide, magnesium oxide or the like, to form a surface oxide deposit 14 on the mandrel 10 using

  of a conventional plasma torch 16 It has been shown that such reve

  oxide coatings have an adhesion and form a durable coating on a metal surface such as the surface of the

chuck 10.

  The oxide coated mandrel is then introduced into

  a low pressure RF plasma deposition chamber (not shown

  in which the mandrel 10 is mounted to undergo a rotational movement under a planma torch 20 coming from an RF plasma gun 18 Such an RF gun can be as described in the abovementioned patents, such as the state patent -United

from America 4,782,884.

  The RF 18 plasma gun is used to deposit a layer 22 of a titanium-based metal such as Ti-6242 (titanium 6 aluminum 2 tin 4 zirconium 2 cobalt) on the surface 14 coated with oxide of the mandrel 10 The layer formed may for example have a thickness of about 3 mm (1/8 inch) The preferred thickness of the layer depends on a small number of factors A first factor is that the formed ring must stand by itself and the thickness of the layer must be sufficient to provide a ring of sufficient wall thickness to ensure the holding of this ring Another factor lies in the intended use of the ring If the outer surface of the ring must be worn , an additional thickness suitable for removing

  metal by machining must be provided.

  For other reasons, the internal position of a deposited ring of matrix metal is a sacrificial part of a reinforced ring structure for use as an element.

  of a set of concentrically nesting rings and of conso-

  bind into a ring of more than 100 layers of reinforcing filaments

  cement This is a sacrificial part in that it is removed by machining the interior of a 20-layer ring

  of the whole after the 20 layers of reinforcement

  have been added but before the five rings have been

  health are assembled in a concentric network and consolidated

  in a super ring or a single ring of more than 100 layers.

  The inner layer of the matrix mntal of each of

  rings to be assembled is sacrificed, i.e. machined and rejected

  tee, to increase the volume portion of filaments of each

cxxcomponent ring of the assembly.

  After the deposition of the layer 22 of matrix metal, the ring and the mandrel are allowed to cool. The ring 22 separates spontaneously from the mandrel and slides out of the mandrel.

  the way represented in figure 3.

  The process according to the invention and the way in which it can

  to be implemented is illustrated by the following example.

EXAMPLE 1

  A hollow mild steel ring with a length of

  cm and a diameter of 10 can was provided The steel had a coef-

  thermal expansion approximately 14 x 10-6 OC-1 The hollow ring was mounted for deposition by spraying under normal pressure plasma of a surface coating with a thickness of 0.075 to 0.125 mm (0.003 0.005 inch) aluminum oxide Le

  plasma gun used was a Metco 3 MB using the condi-

  spraying options suggested by Metoco The chuck first

  heated by the plasma torch and then the aluminum oxide layer

  minium was deposited by spraying.

  After the normal oxide deposition of the aluminum oxide

  nium, the mandrel was introduced into a low-pressure RF plasma deposition chamber similar to that described in the aforementioned US patents. The hollow oxide-coated ring was then heated by the plasma torch to a sufficiently high temperature. to deposit a matrix metal The matrix mnetal applied was a titanium-based alloy and more particularly Ti 6242 (Ti-6 Al-2 Sn- 4 Zr-2 Mo) The coefficient of thermal expansion of the matrix metal titanium based alloy deposited was approximately 11 x 10 o-6 C-1 After depositing a thickness of approximately 3 mm (0.125 inch) of the titanium based alloy matrix, the mandrel and its oxide and mnetal coatings were allowed to cool to room temperature and then removed from the low pressure plasma deposition chamber After removal from the chamber, it turned out that the

  matrioe's metal ring had separated spontaneously and automatically

  oxide coated mandrel so that it was possible to slide the ring out of the mandrel without using

  chemical agents, machining or other destructive steps.

  It will be noted that the implementation of the method according to the present invention depends both on the coating of the mandrel by

  a non-reactive oxide coating and the existence of a different

  notable rene of coefficient of thermal expansion between the metal of the mandrel and the matrix metal deposited on its part coated with oxide Significant differences in coefficients of

  thermal expansion are required for satisfactory operation

  making the present invention and preferably the differences in coefficients of thermal expansion should also be

as high as possible.

  After depositing the titanium-based metal ring and removing it from the oxide-coated mandrel, the mandrel was again sprayed with additional A 1203 to supplement the amount that was incorporated into the matrioe ring when it

  has separated from the oxide-coated mandrel The mandrel with its new

  Calf oxide coating was introduced into the low pressure plasma deposition chamber and heated to deposit a second ring of matrix metal. The matrix metal of the same titanium alloy was formed on the surface of the mandrel and again the mandrel and ring were cooled to room temperature and then removed from the low pressure plasma deposition chamber Again, the ring spontaneously separated from the oxide coated mandrel and was removed from the mandrel without assistance from agents

mechanical or chemical.

  The internal diameter of the two rings formed as described in the example was measured and found to be identical

  to better than 0.075 to 0.125 ma (0.003 to 0.005 inch).

  The above demonstrates that it is possible to produce a multiplicity of ring structures having fundamentally

  the same internal diameter by the process of the present invention

tion.

Claims (5)

  1 Method for manufacturing a plurality of ring structures having practically the same diameter, characterized in that it comprises the following steps: providing a mandrel (10) with a high coefficient of thermal expansion,   coating the mandrel with a low reactivity oxide (14)   quickly, place a ring (22) by RF plasma spraying   of a matrioe metal with a low coefficient of thermal expansion   mique on the oxide coated surface of the mandrel,   allow the mandrel and the ring to cool to provo-   that a spontaneous separation of the ring from the mandrel, and   repeat spray deposition and cool   several times to form a plurality of rings having   practically the same internal diameters.   2 Method according to claim 1, characterized in that   that the deposited oxide is aluminum oxide.   3 Method according to claim 1, characterized in that the coating of the mandrel with oxide is carried out by plasma spraying.   4 Method according to claim 1, characterized in that   that the matrix metal is a titanium-based metal.   Method according to claim 1, characterized in   that the matrix metal is Ti-6242.   6 Method according to claim 1, characterized in that   that the matrix ring has a thickness of approximately 3 mmin.