DEPOSITING MATERIAL ONTO A SUBSTRATE

Abstract: The invention relates to methods of depositing a material onto a substrate. In one example, the method comprises placing the substrate (23) on a mould (22) having a groove (21); and causing relative frictional movement between the substrate (23) and the consumable of the material while urging the consumable onto the substrate and against the mould (22) to generate a plasticised layer of the material. The urging action causes the substrate (23) to deform across its thickness into a groove shape, the material being deposited in the groove thus formed.

Description: DEPOSITING MATERIAL ONTO A SUBSTRATE The invention relates to methods of depositing a material onto a substrate comprising the step of causing t relative frictional movement between the substrate and a 5 consumable of the material while urging the consumable onto •» the substrate to generate a plasticised layer of the material. Such methods, referred to generally as friction surfacing, are well known and were proposed initially in GB-A-572789. 10 Friction surfacing is used in particular for applying hard facing materials onto blades and farm machinery as described by Vavilov and Voinov in Friction Welding, 1964, pages 7,8, 98 and 99. Recently, friction surfacing methods have been developed enabling a wide variety of materials to 15 : be laid down. For example, in EP-A-0460900 we describe methods for laying down ceramic materials, such as metal matrix composites. Relatively thick deposits up to 2 mm or more can be laid down in one pass. FR-A-1365426 addresses the problem of providing a 20 surface deposit on a flat surface, the other side of the substrate bearing the surface requiring a relief. This problem is solved by urging the substrate against a mould having the relief pattern during the friction surfacing process so that a flat surface is laid down on one surface, 25 while the underside of the substrate is provided with the relief. Thus, surfacing by frictional means is well established for a variety of metals, alloys and composites with deposition ranging in thickness from about 0.1 mm to 30 over 2 mm for a variety of applications. Multiple deposition both adjacent side by side and cumulative one * above another is readily carried out to extend the overall width of the deposited material or its overall thickness. * Deposits can be made on flat or simple curved surfaces or 35 in recesses in the plane of the substrate against which the consumable member is pressed to generate heat by relative movement either rotational or oscillatory. However, a fundamental problem with this process (which has not been overcome in the long period of history of the process and its application) is the lack of bond or reduced quality of bond produced towards the edges of the deposit. This is largely due to the lack of pressure at the outer edges of the plasticised zone (irrespective of the load applied to the consumable member) and the relative velocity of its movement with respect to the substrate. Thus, in practice a considerable amount of the deposited layer is of reduced effectiveness and in general is cut off, leading to wastage of materials of high integrity and often of relatively high cost. As illustrated in Figure 1, the deposit with a circular consumable member 1 of diameter 10 or 15 mm rotating at 1000-1500 rpm provides a deposit 2 of which 25% is not well bonded to the substrate 3. This is normally cut off or not utilised. Even when the deposit is laid in a groove 4 with chamfered sides, the bonding at the edges is inferior to the bonding in the central region (Figure 2A) . In practice the deposited material either does not fill the groove (as shown in Figure 2A) or, if it does, it can as illustrated in Figure 2B spill over on the upper edges, again with reduced or no bonding between the deposit and the substrate in these regions. To remove these less well bonded areas, the deposit is machined or ground, and often considerably reduced in thickness in order to provide a uniform layer albeit at the cost of wasting a significant proportion which may be as great as 30% or more of the material deposited. In accordance with one aspect of the present invention, a method of depositing a material onto a substrate comprises placing the substrate on a mould having a groove; and causing relative frictional movement between the substrate and the consumable of the material while urging the consumable onto the substrate and against the mould to generate a plasticised layer of the material, wherein the urging action causes the substrate to deform in the thickness direction into a groove shape, the material being deposited in the groove thus formed. With the invention, an effective bond is produced substantially throughout the deposit by shaping the deposit and substrate as the deposit is being made. This also reduces the amount of material wasted (compared with that normally experienced) . Typically, the groove will be double sided although in some cases, an open sided groove could be formed. The method typically further comprises causing relative traverse movement between the consumable and the substrate whereby material is deposited along an elongate groove. The relative frictional movement between the consumable and the substrate can take any known form including one or a combination of rotation, orbital movement, and linear oscillatory movement. Examples of different types of relative frictional movement are described in EP-A-0434430 and EP-A-337691. A common application of friction surfacing is in tool tipping (e.g. providing hard facings on blades) , or manufacture of punches and dies, in which a suitable hard material is deposited onto a suitable substrate which is subsequently machined or ground to the desired profile. For example, in the manufacture of blades (which was one of the first applications of friction surfacing described in the literature) , it is obviously desired to obtain a good bond near the extremity of the exposed end of the blade or die between the deposit and the substrate. As already indicated the quality of bond at the edge of the deposit in friction surfacing is poorer than that obtained in the more central regions. Thus normally a considerable amount of material must be removed before the high quality bond region is reached. In accordance with a second aspect of the present invention, a method of depositing a material onto a substrate comprises causing relative frictional movement between the substrate and a consumable of the material while urging the consumable onto the substrate to generate a plasticised layer of the material, the material being deposited into a groove having opposed sides in the substrate; and removing part of the substrate including one of the opposed sides of the groove to expose part of the deposited material. In contrast to the post-friction machining techniques previously used, this method enables post machining to be avoided by removing part of the substrate and possibly also part of the deposited material to expose part of the remaining deposited material. Removal of the substrate (and deposited material) can be achieved simply by cutting or splitting the deposit and substrate. However, in one preferred case, the substrate is in two parts whereby one of the parts can be removed after the depositing process thus revealing part of the deposit. The part of the substrate removed will be shaped so that the exposed part of the deposit has the required shape without post machining being necessary. The invention is applicable for use with any pair of materials which have been bonded by friction surfacing in the past. For example, the bonding of aluminium, steel or metal matrix composites to a substrate such as titantium. In some applications, the depositing of material into a groove of the substrate can be carried out using a method according to the first aspect of the invention. Some examples of conventional methods and methods according to the invention are illustrated in the accompanying drawings, in which:- Figure 1 is a schematic cross-section through one conventional deposit; Figures 2A and 2B illustrate cross-sections through two further conventional deposits; Figure 3 illustrates a first example according to the invention; Figure 4 illustrates a second example according to the invention which makes use of a sacrificial support; Figure 5 illustrates a third example of the invention similar to that shown in Figure 4 but with a shaped, sacrificial support; Figure 6 illustrates a fourth example according to the invention for manufacturing a pair of blades; Figure 7 illustrates a fifth example of the invention for providing hard facings on a pair of previously formed blades; Figure 8 is a plan of the blades used in Figure 7 prior to the deposit step; Figure 9 illustrates a modified form of the Figure 7 example. Figure 10 illustrates a sixth example of the invention in which a groove is formed in a substrate during the surfacing process; Figure 11 illustrates the substrate of Figure 9 after the deposit process; and, Figure 12 illustrates the formation of a double edged blade. In the example shown in Figure 3, a substrate 4 with a typical thickness of 5-10 mm has a preformed groove 5 formed in it, the groove 5 having a substantially 45° chamfered edge 6 along one side and a shallower, typically 20° chamfered edge 7 along the opposite side. A friction surfacing process is then carried out in a conventional manner to deposit material 8 into the groove 5 by relatively rotating a consumable member (not shown) which is urged under pressure into the groove 5 while laying down material in the groove. Typically, the consumable diameter is similar to the groove dimension so material can be laid down in a single pass. The resulting deposit is automatically moulded or shaped by the form of the groove into the desired shape so that if a section 9 of the substrate 4 having a surface including the edge 7 of the groove and cut along a dashed line 9' is subsequently removed, the deposit 8 is exposed and already has the required shaped edge and is thus suitable as the edge of a blade, for example, after grinding or sharpening. The extremity 30 of the substrate/deposit bond is in a region spaced from the original outer edge of the deposit and thus provides a strong bond. Typically in this and the examples to be described, the groove is elongate (being shown in cross-section in the drawings) , the consumable and substrate undergoing relative lateral movement so that a deposit is laid down along the groove. In the example shown in Figure 3, section 9 initially forms an integral part of the substrate 4. In the Figure 4 example, a separate ceramic or sacrificial member 10 is : mounted alongside the substrate 4 to define an open side of the groove 5. The support 10 is preferably formed of a material which is not metallurgically bonded to the deposit 8. As illustrated in Figure 4, the deposit 8 bonds well to the substrate 4 up to the extremity of the substrate, since this is positioned in the region of high applied pressure from the plasticised zone due to the applied load on the consumable member. Regions of reduced pressure and hence reduced bonding would occur further to the extremity, but in this case are not relevant since the support material 10, (such as ceramic) is utilised which does not readily bond to the material deposited. Alternatively for the support material a high strength high temperature alloy may be used such as a monel alloy which, for normal hard facing materials such as tool steel and stellite, does not readily bond to the deposit during friction surfacing. To ensure good bonding at the extremity of the substrate, the further support material 10' can be of slightly reduced thickness in this region and furthermore may comprise a retaining wall or chamfer 11 (see Figure 5) to help maintain reasonable pressure towards the extremity of the deposit on to the substrate. These arrangements are particularly suited for applications in punches and dies, as well as cutting blades and the like where the chamfer 11 is made at the required cutting edge angle. Figure 6 illustrates a further example which is particularly suitable for dies and punches and the like, and which may also be adapted for blades and cutting edges. In this case, a substrate 12 is provided which is substantially symmetric about a plane 13 and has an elongate double sided groove 14 positioned centrally about the plane 13. Material 8 is deposited in the groove 14 using a conventional friction surfacing method. Following the depositing step, the substrate 12 and deposit 8 are split into halves along the plane 13 so as to generate a pair of separate blades. One of the main advantages of this technique is that the edges of the punches or blades which are produced arise from the central region of the deposit 8 which is of the highest quality in terms of bond strength and microstructure. The outer edges of the deposited layer can be subjected, if desired, to a further applied load using a bush or sleeve, for example, which squeezes the so-called flash and increases the pressure in the region of normally lower quality bonds, or they may be allowed to form a natural resultant to the process since quality demands in these regions are less stringent. Figure 7 illustrates a variant of Figure 6 in which a pair of substrates 15,16 of similar form are brought together and abut along a line 17. Each substrate 15,16 has an elongate, open sided groove 18,19 respectively. This arrangement is shown in plan form in Figure 8. The butted blades 15,16 are then provided with a deposit in the resultant, double sided groove in a similar manner to that shown in Figure 6. Following the laying down of this deposit, the deposit is split in a line parallel with the line 17 thus producing a pair of hard faced blades. Figure 9 illustrates a modification of the Figure 7 embodiment in which a ceramic insert 20 extends between the substrates 15,16. This assists in separating the blades following the deposition of material. In a further arrangement (Figure 10) , which is particularly suitable for relatively thin substrates, a channel or groove 21 having a depth of 5mm for example and a width (as seen in Figure 10) of say 30 mm is formed in a mould 22 which supports a substrate 23 having a thickness of 4mm. During the friction surfacing process, the consumable (not shown) with a diameter of about 25mm is urged onto the upper surface of the substrate 23 in the region spanning the groove 21 so that the relatively thin substrate 23 is caused to deform and bend into the groove or channel 21 so as to form a grooved substrate 23 • (Figure 11) with deposited material 24 in the groove. Here the : bond quality of the edges of the deposit is enhanced by further bending action enforced on the substrate 23 particularly onto the sloping sides of the groove so formed. This arrangement may be used for double ended components as shown in Figure 7 or to provide shaped deposits with better quality bonds at their outer extremities than found with friction surfacing with the preformed substrate. This also provides for more economic manufacture since the substrate itself does not require pre-machining and only the mould is appropriately machined but is utilised repetitively for further components. The techniques shown in Figures 10 and 11 can be used in particular for providing hard facings on double edged blades as shown in Figure 12. In this case, in a first step a mould (not shown) will be provided having an open ended groove conforming to a groove 25 in the finished blade. A substrate 26 is then laid onto the mould and the friction surfacing operation performed in a manner similar to that described with reference to Figures 10 and 11. In this way, a deposit 27 is formed in the groove 25 produced in the substrate 26. The substrate 26 is then inverted and the process repeated so that a deposit 28 is formed in a groove 29.

Claims: CLAIMS 1. A method of depositing a material onto a substrate, the method comprising placing the substrate on a mould having a groove; and causing relative frictional movement between the substrate and the consumable of the material while urging the consumable onto the substrate and against the mould to generate a plasticised layer of the material, wherein the urging action causes the substrate to deform in its thickness direction into a groove shape, the material being deposited in the groove thus formed. 2. A method according to claim 1, further comprising causing relative traverse movement between the consumable and the substrate whereby material is deposited along an elongate groove. : 3. A method according to claim 1 or claim 2, wherein the groove has opposed sides. 4. A method of depositing a material onto a substrate, the method comprising causing relative frictional movement between the substrate and a consumable of the material while urging the consumable onto the substrate to generate a plasticised layer of the material, the material being deposited into a groove having opposed sides in the substrate; and removing part of the substrate including one of the opposed sides of the groove to expose part of the deposited material. 5. A method according to claim 4, wherein only a part of the substrate is removed. 6. A method according to claim 5, wherein the part of the substrate removed defines an inclined side of the groove. 7. A method according to claim A , wherein the removing step comprises dividing the substrate along a plane extending along the groove. 8. A method according to claim A , wherein the substrate is defined by a pair of butting substrate sections, each section having an open ended groove, the grooves opening into each other to define the double sided groove. 9. A method according to claim 4, wherein the step of providing material in the groove is carried out by performing a method according to any of claims 1 to 3.

Inventors: NICHOLAS EDWARD DAVID, THOMAS WAYNE MORRIS, NICHOLAS, EDWARD, DAVID, THOMAS, WAYNE, MORRIS
Applicants: WELDING INST, THE WELDING INSTITUTE
Application year: 1991
Main classification: C23C26
IPC codes: B23K20, C23C26