US-20260124671-A1 - CASTING METHOD AND APPARATUS

Abstract

A mould element (such as mould core) for casting metal is made by a process that starts with a coated mould element having a coating (such as a core coating). The coated mould element is provided with a further coating and a bond coating on the further coating, the bond coating allowing the further coating to attach to a metal casting made with the mould element, such as a cast housing for a turbomachine.

Inventors

• Tongjun GAO
• Kaifeng Wu

Assignees

• WUXI CUMMINS TURBO TECHNOLOGIES COMPANY LTD.

Dates

Publication Date

20260507

Application Date

20221013

Claims (18)

1. 1 . A process of forming a mould for casting metal, the process including: a) providing a coated mould element; b) providing a further coating on the coated central mould element; and c) providing a bond coating on the further coating.
2. 2 . The process according to claim 1 , wherein providing a coated mould element includes providing a sand-based mould element having a water-based core coating.
3. 3 . The process according to claim 1 , wherein one or both of the further coating and the bond coating are provided via thermal spraying and/or dipping.
4. 4 . The process according to claim 1 , wherein the further coating is a coating selected from a thermal barrier coating, an anti-corrosion coating, a friction-reducing coating, an oleophobic coating, a hydrogen-embrittlement protection coating, an anti-oxidation coating, an anti-erosion coating, and an anti-fouling coating.
5. 5 . The process according to claim 1 , wherein the mould element is a central core.
6. 6 . The process according to claim 1 , wherein the mould element is in the shape of an internal passage of a turbomachine, optionally in the shape of an internal volute of a turbine housing of a turbomachine.
7. 7 . A method of casting a housing for a turbomachine having an internal coating, the method including: a) providing a multi-layered core having a central core, a core coating, a further coating, and a bond coating in said order; b) providing a casting mould including the multi-layered core, said casting mould and multi-layered core defining a cavity; c) introducing molten metal into the cavity; and d) allowing the molten metal to solidify in the cavity to form a housing casting intermediary.
8. 8 . The method according to claim 7 , wherein the further coating is selected from a thermal barrier coating, an anti-corrosion coating, a friction-reducing coating, an oleophobic coating an anti-oxidation coating, an anti-erosion coating, a hydrogen-embrittlement protection coating, or an anti-fouling coating.
9. 9 . The method according to claim 7 , wherein the method further includes removing the central core and the core coating thereby leaving the bond coating and further coating on the surface of the housing casting intermediary.
10. 10 . A mould element for use in casting metal, the mould element including: a) a central mould element b) a mould element coating on the central mould element c) a further coating on the mould element coating; and d) a bond coating on the further coating.
11. 11 . The mould element according to claim 10 , wherein the mould element coating is a water-based mould element coating.
12. 12 . The mould element according to claim 10 , wherein the bond coating includes a metal which forms the bulk of the intended casting material, preferably iron or aluminium.
13. 13 . The mould element according to claim 10 , wherein the further coating is selected from a thermal barrier coating, an anti-corrosion coating, a friction-reducing coating, an oleophobic coating, a hydrogen embrittlement protection coating, an anti-oxidation coating, an anti-erosion coating, or an anti-fouling coating
14. 14 . The mould element according to claim 10 , wherein the mould element is a core.
15. 15 . The mould for producing a housing of a turbomachine, the mould including a mould element according to claim 10 .
16. 16 . A housing for a turbomachine, the housing including an internal volute surface, wherein the internal volute surface includes a barrier coating bonded to the internal volute surface of the housing via a bond coating.
17. 17 . The housing for a turbomachine according to claim 16 , wherein the barrier coating is selected from a thermal barrier coating, an anti-corrosion coating, a friction-reducing coating, an oleophobic coating, a hydrogen embrittlement protection coating, an anti-oxidation coating, an anti-erosion coating, or an anti-fouling coating.
18. 18 . A turbine housing manufactured according to claim 1 .

Description

TECHNICAL FIELD The present invention relates to a process of forming a mould element for casting metal, a method of casting a housing for a turbomachine, a mould element for use in casting metal, a mould for producing a casting, a housing for a turbomachine, and a casting or turbine housing manufactured according to the aforesaid process or method or utilising the aforesaid core or mould. The mould element is preferably, but not exclusively, a mould core, which may be simply referred to as a core. The present invention has particular, but not exclusive, application to the manufacture of turbomachine turbine housings which include one or more protective coatings. BACKGROUND OF THE INVENTION Turbochargers are well-known devices for supplying air to the intake of an internal combustion engine at pressures above atmospheric pressure (boost pressure). A conventional turbocharger essentially comprises an exhaust gas driven turbine wheel mounted on a rotatable shaft within a turbine housing. Rotation of the turbine wheel rotates a compressor wheel mounted on the other end of the shaft within a compressor housing. The compressor wheel delivers compressed air to the inlet manifold of the engine, thereby increasing engine power. The turbocharger shaft is conventionally supported by journal and thrust bearings, including appropriate lubricating systems, located within a central bearing housing connected between the turbine and compressor wheel housing. In known turbochargers, the turbine stage comprises a turbine chamber within which the turbine wheel is mounted; an annular inlet passageway defined between facing radial walls arranged around the turbine chamber; an inlet volute arranged around the inlet passageway; and an outlet passageway extending from the turbine chamber. The passageways and chambers communicate such that pressurised exhaust gas admitted to the inlet volute flows through the inlet passageway to the outlet passageway via the turbine and rotates the turbine wheel. Metal castings are commonly made by introducing liquid metal into a mould and then allowing the liquid metal to solidify. For metal castings which have a complicated shape, such as those which define a volute or cavity, it is often necessary to use a mould which includes a core. The core can be an intrinsic part of the mould or a separate piece. Various types of mould exist depending on the type of casting being undertaken. For example, for components which have thin walls, high pressure die casting may be used. In high-pressure die-casting, liquid metal is provided into a mould cavity under pressure where it is held until it has solidified sufficiently. The mould, also referred to as a die, is then opened to release the casting. This cycle can then be repeated to produce further castings. Another type of moulding is sand moulding where a mould and/or core are formed of sand which includes binder additives to allow the mould to retain the desired shape. A surface coating may be provided in order to reduce or prevent gases released from the breakdown of binder additives in the mould due to the high temperatures involved in metal casting from damaging the surface of the casting. For example, acidic gases may be released from the mould and these may cause damage to the surface of the casting. The casting may be released from a sand mould by breaking the sand mould and the casting may then be fettled to remove excess mould material and any casting irregularities after release from the mould. Housings for turbomachines can be made by casting in a sand mould. After release from a mould, castings may require treatment to provide a protective coating on a surface thereof. Whilst this may be straightforward in cases where the casting is of a simple shape or where the casting can simply be dipped, it is much more difficult for castings which have complex shapes, particularly ones with internal surfaces. The additional difficulty in protecting complex shapes incurs additional costs and may still result in a less consistent protective coating being applied, which can lead to the protective coating detaching from the surface or otherwise failing. CN111230048 describes methods for manufacturing cast components with integral thermal barrier coatings. This is achieved by providing a core coated with a thermal barrier coating, disposing the core within a casting mould, casting metal around at least a portion of the coated core to form a casting intermediary, and then removing the core from the casting intermediary to form a cast component. An outer metal layer may be applied to the thermal barrier coating. The present invention has been provided to address at least some of the deficiencies of the prior art. SUMMARY The present invention aims to provide new and useful methods and assemblies for use in the manufacture of castings, particularly housings for turbomachines, which include at least one functional layer, such as a protective or thermal barrier lay