Hybride part and method to manufacture

The invention relates to hybride part comprising a first portion and a second portion, wherein an interface defines said first portion from said second portion and a channel extends from said first portion through said interface into said second portion.

Further the invention relates to a method to manufacture said hybride part . Additive manufacturing or 3D printing is a process of making three dimensional solid objects with a high degree of freedom of the design according to a 3D virtual module. Basically the object is created by providing layers of material to a substrate or a platform whereby the final object can have a lay- ered material structure. The object can be made by additive manufacturing in total without being one piece of material with the substrate.

Today several additive technologies are known, for example selective laser sintering, direct metal laser sintering, fused deposition modeling, stereo lithography, digital light processing, fused filament fabrication, melted and extrusion modeling, laminated object manufacturing, electron beam melting, selective heat sintering or powder bed and ink head 3D printing.

From DE 44 00 315 CI it is known to lithographically add layers of material to a part to build a micro-structure. A high degree of accuracy is needed to avoid any significant offset in channels extending from a substrate into the added material . From US 2007/0275210 Al it is known to layerwise generate a honeycomb seal .

From EP 1295846 a multilayered microdevice structure compris- ing channels is known.

This invention concentrates on additive technologies which enables the generated composite part to be used in a gas turbine burner. The most interesting technologies are therefore selective laser sintering, direct metal laser sintering or fused deposition modeling. Since these additive technologies are comparatively young developments, design adjustments have not been performed so far to optimal exploit the advantages of these technologies as it is done for conventionally pro- duced parts. Conventional production here means mature technology for example casting, milling or turning.

Especially advantageous is additive manufacturing in the field of service and refurbishment for example of burner heads of gas turbines. If a burner head of a gas turbine made to inject fuel and maybe oxygen containing gas into a combustion chamber is worn out by for example erosion, it is conventionally completely replaced. By using additive manufacturing a part of this burner head can be cut off and the re- maining part can be used as a substrate for additive manufacturing, for example selective laser melting. Here it is, however, very difficult to adjust the position of the used part accurately to guarantee that tiny channels in the first existing part are placed correctly to be continued by the se- cond part to be generated by the additive manufacturing onto the substrate. Normally the aim is to exactly continue these channels extending through the old piece of material into the new piece of material across the interface between these two parts without any position shift restricting the average di- ameter of said channel at the interface. It is therefore up to now not an interesting option to rework such parts as described above since an offset can merely be avoided. It is one object of the invention to improve the design of a part of the incipiently mentioned type such that refurbishment by additive manufacturing can be done without significant quality restriction in the resulting part. It is another object of the invention to provide a method of performing additive manufacturing on an existing first part of the incipiently mentioned type resulting in a final product without significant quality restriction. The invention solves the above objects by a hybride part of the incipiently defined type with the additional properties of claim 1. Further the invention proposes a method according to the claims to overcome the above problems. The respectively dependent claims relate to preferred embodiments of the invention.

It is essential, that the hybride part of said first part and said second part is finally one piece of material. Said first portion can be made by any production method, for example conventionally machining as milling, turning or casting. Channels in this first part can also be provided by any manufacturing method, especially by drilling or electro dynamic machining. Said first part can be done also by additive manufacturing.

Said second part is provided by additive manufacturing as defined above. It is essential that the first part solves as a substrate for the second part in the area of said interface. The invention overcomes the problem that every manufacturing process is limited in accuracy and especially in the area of refurbishing a part during the above described cutting and adding material method. Conventionally additive manufacturing adds up inaccuracies to a magnitude which is not too tolera- ble regarding tiny geometries as channels continuously extending through said first part and said second part. Considering the tininess of these channels it is possible that channels do not even meet due to the limits of accuracy of the respective production methods.

The invention makes the above defined production processes more capable to deal with tingly geometries without spending extensive effort into increasing accuracy. The invention makes the design itself more tolerable for inaccurate manufacturing and safes thereby time and costs. Further the invention simply enables some designs to be done as a hybride part as defined above which were due to accuracy problems not possible before.

One preferred embodiment provides said channel having a first section at said interface and a second section at a specific distance remote from said first element, wherein an average third diameter of said channel at said second section is nominally the same as said first diameter. This design feature enables the best approximation of the channel geometry generated by additive manufacturing to a part which was made of one piece and by one single manufacturing process. If the channel ends in said second part into a nozzle remote from said interface, this nozzle will be nearly not influenced by any offset of the channel in the area of the interface with regard to fluid dynamic properties of said channel . Prefera- bly the cross-section of said channel is shaped round but can be of any geometry.

The average diameter referred to in this document is the diameter of a circle surrounding an area identical to a cross section of said channel.

The preferred application of the invention is a method to refurbish parts by first machining away or cutting off a portion to be replaced, and replacing it by said second portion.

According to the invention this method of rework is preferably applied to gas turbine parts, especially to gas turbine burner parts. The above mentioned attributes and other features and advantages of this invention and a manner of attaining them will become more apparent and the invention itself will be better understood by reference to the following description of the currently best mode of carrying out the invention taken in conjunction with the accompanying drawings, wherein

Figure 1 shows a schematic depicting of a hybride part according to the invention made by a method according to the invention .

Figure 1 shows a schematic depiction of a hybride part P according to the invention comprising a first portion FP and a second portion SP meeting each other at an interface IF defining said first portion FP from said second portion SP. A channel CH extending from said first portion FP through said interface IF into said second portion SP. Said channel CH in said first portion FP extends along a central first axis XI and in said second portion SP said channel extends along a second axis X2. Said first axis XI and said second axis X2 are nominally meant to be identical but are offset from each other by an offset OFF duet to manufacturing or alignment inaccuracies. Said second portion SP is build up on said inter- face IF of said first portion FP by additive manufacturing. In this example said SP was build up by laser sintering.

Said channel CH in said first portion FP has a first diameter Dl especially in the area of said interface IF. Said channel CH in said second portion SP in the area of said interface IF has a second diameter D2 , which is larger than Dl . With increasing distance to said interface IF said channel CH in said second portion SP is tapered along o first taper portion TP till said channel diameter reaches a third diameter D3. Said third diameter D3 here is identical with said first diameter Dl . Diameter here means that the design has a nominal identical average diameter, which can deviate according to manufacturing accuracy. In this example of figure 1 the tapering is conical with a conus-angle of a . However the tapering can have any geometry including a tulip shape aimed to reduce turbulence if said channel CH conducts a process fluid PF especially into the direction from said first part FP to said second part SP. Preferably said channel is designed to conduct a process fluid PF in the direction from said first portion FP to said second portion SP with reduced pressure loss. Preferably said channel CH extends all the way through said second part SP, wherein said channel CH might join into a nozzle NZ .

According to the method of the invention to manufacture the hybride part P in a first step said first part FP is provided and said channel CH extends along a first central axis XI through said first part FP .

In a second step material is added by additive manufacturing to said interface IF in order to build up said second portion SP. Said channel CH in said second portion SP is than provid- ed with the above described geometry.

Preferably said offset OFF between said first axis XI and said second axis X2 is less than (D2 - Dl) preferably (D2- Dl) /2.