WO1982004375A1

WO1982004375A1 - Wear-resistant materials

Info

Publication number: WO1982004375A1
Application number: PCT/GB1982/000167
Authority: WO
Inventors: & Ryder Ltd Anderman
Original assignee: Real Michael William; Cooper Derek Redvers
Priority date: 1981-06-09
Filing date: 1982-06-04
Publication date: 1982-12-23
Also published as: EP0080473A1; ZA824048B

Abstract

The material comprises a metal plate (16) with perforations or cavities (17) containing harder oxide ceramic platelets (18) which are disposed parallel to the wear surface with webs of metal between which is in no case smaller in width than the thickness of the platelets. In the landside (12) of a mouldboard plough the platelets (18) are of parallelogram shape. They are of sintered alumina ceramic and secured in a mild steel or other ferrous metal plate by epoxy adhesive. The landside is fastened by bolts (14 and 15) and the recessed head of bolt (15) is protected by ceramic disc forward of the bolt head to reduce wear at the edge of the recess. In another embodiment a regular array of circular ceramic discs are mounted in a perforated metal plate.

Description

WEAR-RESISTANT MATERIALS

The present invention relates to wear-resistant materials. It is well known that metal plate or sheet materials can be made more wear-resistant by changes in their composition (alloying) or by surface treatments after formation. The expense of selecting special materials and/or carrying out hardening processes is frequently greater than can be justified by the increase in component life which is obtained. It is also known to protect metal surfaces by applied coatings or by the application of tiles of alumina or other ceramics. In this case softer metals can be used, for example mild steel instead of an alloy steel, and very good abrasion resistance is obtained, but if the tiles are subject to the action of large particles or lumps cracking takes place as a result of impact and the tiles tend to tear away from the underlying metal.

There is a large range of applications, particularly in the materials handling field, where a wear-resistant material of improved performance which can be produced without a large increase in price would be useful.

British Patent Specification No. 1,480,057 describes the use of blunt or broken cutting tool blades in the form of lamellae composed of metallic carbides, nitrides, borides and/or silicides to form wear zones on metallic bodies. In some examples the lamellae lie parallel to the surface of the wear zone and are secured in position in a groove or recess by means of solder or adhesive. In other examples the lamellae are edge-on to the wear zone and are cast into the metallic body. While this may be a valuable way of using up old cutting blades, it is not a satisfactory method for obtaining good wearresistance at a reasonable cost. In accordance with the present invention there is provided a wear-resistant material comprising a metal plate with a number of cavities or perforations formed therein, each of which has secured in it a platelet of oxide ceramic material of greater wear-resistance than the metal, the thickness of each platelet being disposed generally perpendicular to the surface of the metal plate so that the faces of the platelets are generally parallel to the surface of the plate, and the distance between adjacent platelets being in no case less than the thickness of the platelets.

The oxide ceramic material, which is preferably composed principally of alumina, can be preformed as platelets of any desired shape by known pressing and sintering techniques. The metal plate, which is usually iron or steel, is also preformed by conventional techniques. Perforated metal plate, for example, is readily available as a standard industrial product. The securing of the platelets in their cavities may be achieved simply by a mechanical fit resulting from the relative shape and dimensions or may be aided by the use of cement or adhesive. In either case the cooperation of the hard ceramic material and the softer and more ductile metal around it results in exceptional wear-resistance and greatly increased life. Cracking of the platelets is minimized because of their relatively small area and the support afforded by the surrounding metal while the metal itself is protected against wear by the harder ceramic which may make up 50% or more of the total area in the wear zone. It is important in order to secure the improved wear resistance that the platelets be parallel with the surface of the plate so that their faces form a substantial part of the wear zone but also that sufficient metal be left between them to give proper support.

In the examples which follow ferrous metals are used because the parts in question are normally made from such merals and they cooperate well with the alumina ceramics. However it is believed that other metals, such as aluminium, can also be used in conjunction with oxide ceramics and improvements in wear resistance will be obtained with such combinations.

The platelets may be discs but are not necessarily circular. Perforated metal plate with circular perforations is readily available and in this case circular ceramic discs with a thickness approximately equal to that of the metal plate are preferably used. However noncircular perforations having a rounded contour are also obtainable and other shapes of perforation or cavity can be made without too much difficulty. In each case the platelets are shaped to the appropriate contour. Normally the thickness or depth of each inserted platelet will be less than the minimum overall dimension of its face.

Commercial perforated sheet metal commonly has webs between the holes which are no narrower than the thickness of the sheet. For the thickest sheet the resultant open area can be about 50% and larger open areas can be obtained when the same size of hole is used on thinner sheet. When perforated plate is used the two sides can be made equally wear-resistant but in many cases only a single wear resistant surface is required. Commercial perforated plate often has slightly tapering holes and if the platelets are made with a similar taper a tight fit is obtained. It is also possible to use flanges on the discs or to clamp the discs in position from one side and in such cases the use of adhesive or cement is less necessary. For high-temperature applications an aluminous cement may be used. The material in accordance with the invention has the advantage that it can, within limits, be bent and cut on site without specialized equipment. The metal surfaces may, if required, be hardened before the ceramic platelets are inserted.

The invention will now be described in more detail with the aid of example illustrated in the accompanying drawings, in which:-

Fig. 1 is a side elevation of a mould-board plough having a landside constructed of wear-resistant material in accordance with the invention,

Fig. 2 is an enlarged detail of the landside of Fig.1, and Fig. 3 is a perspective view of one bucket of a bucket wheel in which the bucket has a hinged bottom composed of wear-resistant material in accordance with the invention.

In the plough shown in Fig.1 the share is supported by a leg 10 from a beam (not shown). A mould-board 11 lifts and turns the soil while a landside 12 runs along the cut made by the point 13 of the share and thereby keeps the share running straight. The landside 12 runs in sliding contact with the vertical surface of the freshly cut ground and is thus subjected to severe sliding and impact abrasion. The landside 12 is secured to the plough share by coach bolts 14 and 15 to enable it to be removed and replaced. In present ploughs the landside is either made of expensive high-grade steel with the object of prolonging the period between initial fitting and replacement or is made of lower grade material to reduce the cost of replacements. In either case replacement may be made more difficult by corrosion and wear affecting the heads of the fastening bolts even though these are recessed into the surface of the landside. The landside incorporating the invention is shown in more detail in Fig.2. It comprises a plate 16 of mild steel type EN9 in accordance with British Standard 970:1955. The plate is 10 mm thick and in addition to holes for the reception of the fastening bolts 14 and 15 it has eight perforations 17 each of which has a contour of parallelogram shape with rounded corners. The perforations 17 receive ceramic platelets 18 of corresponding shape and thickness which are composed of dense sintered alumina ceramic of 97.5% purity. The platelets 18 are secured in the perforations 17 by means of an epoxy adhesive.

Each of the platelets 18 is arranged with its upper edge in advance of its lower edge with respect to the direction of movement of the plough share. The forward platelet 18A is spaced from the adjacent platelet by a web of metal approximately twice as wide as that separating each of the other pairs of platelets. The perpendicular distance between the inclined sides of these other pairs of platelets is 10 mm, which is equal to the thickness of the metal plate 16. At the rear end of the landside 12, which is where the greatest wear occurs, a steel strengthening plate 19 is welded to the back of the plate 16. The plate 19 extends behind the three rearmost platelets 18 and thus provides additional support for these platelets, more especially against impact loading which might force the platelets out of their perforations.

An additional ceramic insert 20 in the form of a circular disc is disposed in advance of the recess occupied by the head of the bolt 15. This is intended to increase the resistance to wear in the region ahead of the bolt head and thus avoid grooving, thereby preventing increased abrasion of the bolt head.

Fig. 3 illustrates the application of the invention to a basket 21 of a bucket wheel. The bucket 21 is of conventional construction, having scraper teeth 22 at its forward edge to facilitate picking up of the spoil and a hinged bottom flap 23 which is opened at the appropriate point in the roration of the wheel in order to deposit the spoil. The inner surface of the bottom flap 23 is subject to heavy wear by impact and abrasion and to increase its wear resistance it is provided in accordance with the invention with a regular pattern of circular ceramic inserts 24 over its whole surface. The flap is of 10 mm thickness. The ceramic inserts are held in perforations extending through the thickness of the flap. They are arranged in staggered rows with a uniform centre to centre spacing in all directions. The inserts are of 25 mm diameter and at a centre to centre spacing of 35 mm. (They are not shown to scale in the drawing). The inserts cover approximately 50% of the total area.

Claims

CLAIMS :

1. A wear-resistant material comprising a metal plate with a number of cavities or perforations formed therein, each of which has secured in it a platelet of oxide ceramic material of greater wearresistance than the metal, the thickness of each platelet being disposed generally perpendicular to the surface of the metal plate so that the faces of the platelets are generally parallel to the surface of the plate, and the distance between adjacent platelets being in no case less than the thickness of the platelets.

2. A material as claimed in claim 1 in which the metal plate has perforations and the platelets are of a thickness approximately equal to that of the metal plate.

3. A material as claimed in claim 1 or 2 in which the platelets are secured to the plate by cement or adhesive.

4. A material as claimed in any of the preceding claims in which the metal plate is composed of ferrous metal and the platelets are composed principally of alumina.

5. A material as claimed in any of the preceding claims in which the thickness of each platelet is less than the minimum overall dimension of its face.

6. A material as claimed in any of the preceding claims in which the platelets are in the form of circular discs.

7. A material as claimed in claim 6 in which the discs are arranged in a regular array with the same centre to centre spacing in all directions.

8. A landside for a plough comprised of a material in accordance with any of claims 1 to 5.

9. A landside as claimed in claim 8 having platelets of generally parallelogram contour arranged with their short edges parallel to the bottom edge of the landside and with the upper edge of each platelet closer to the forward end of the landside than the lower edge of the platelet.

10. A landside as claimed in claim 8 or 9 wherein a recessed bolt-hole for a securing bolt has a ceramic platelet disposed in a perforation forward of the bolt-hole to reduce wear at the edge of the bolt hole.