This invention relates to additive layer manufacturing, and particularly to making multi-material metal/ceramic gas turbine components by selective laser sintering and selective laser melting of adjacent powder layers of different materials.
Selective layer additive manufacturing includes selective laser melting (SLM) and selective layer sintering (SLS) of powder beds to build a component layer by layer to achieve net shape or near net shape. A powder bed of the component final material or precursor material is deposited on a working surface. Laser energy is selectively directed onto the powder bed following a cross sectional area shape of the component, thus creating a layer or slice of the component, which then becomes a new working surface for a next layer. The powder bed is conventionally spread over the working surface in a first step, and then a laser defines or “paints” the component sectional area on the bed in a following step, for example by raster scanning.
A related process, often referred to as micro-cladding, deposits a powder onto a component via a moving nozzle or other delivery device. A laser concurrently melts the powder at the deposit point, thus forming a bead of material on the component as the delivery device moves. Successive passes can build a layer or layers of material for repair or fabrication of a component.
The invention is explained in the following description in view of the drawings that show:
The inventors have devised a method for additive manufacturing of a component having multiple adjacent materials of different properties. It produces a net shape or near net shape with strong bonding of the adjacent materials, including metal to ceramic. This is especially beneficial in fabricating gas turbine components such as superalloy blades and vanes with ceramic thermal barrier coatings. Such airfoils are difficult to fabricate, because they have complex shapes with serpentine cooling channels lined with turbulators and film cooling holes.
An interface 56 between the first and second powder layers may be delivered so as to form an overlap zone 57 that provides a material gradient transition between the two adjacent powder layers 48, 50. An interface 58 between the second and third powders 50, 52 may be delivered so as to form an engineered mechanical interlock such as interleaved fingers projecting alternately from the second and third powders (later shown). The powder delivery device 60 may have one or more nozzles 62 delivering powder spray 64 to a focal point 66.
The powder delivery device 60 may incorporate multi-axis movements 61 relative to the working surface 54A, so that the nozzle can follow non-linear sectional profiles in a given horizontal plane, can move to different planes or distances relative to the working surface 54A, and can deliver powder at varying angles. The axes may be implemented by motions of the work table 55 and/or the powder delivery device 60 via tracks and rotation bearings under computer control. Powder delivery parameters such as nozzle translation speeds, mass delivery rates, and spray angles may be predetermined by discrete particle modeling simulations to optimize the final slice geometry. After spraying, the powder may be compacted and stabilized by means such as electromagnetic energy and/or mechanical or acoustic vibration prior to laser heating.
The powder may be wetted with water, alcohol, lacquer or binder prior to or during spraying so it holds a desired form until the laser melts or sinters it into a cohesive slice of the component. As described more fully in co-pending United States Patent Application Publication US 2013/0140278 A1, attorney docket 2012P22347US, incorporated by reference herein, flux material may be included with the powder materials to facilitate the cladding process.
The laser energy 69A-B (
86. Delivering a plurality of adjacent powder layers of respective different materials onto a working surface in respective area shapes representing a given section plane of a multi-material component.
88. Overlapping at least two of the adjacent powder layers to form a gradient material zone of transition between said at least two adjacent powder layers.
90. Applying a particular laser energy to each of the powder layers to melt or sinter the layer, wherein at least two of the layers receive respectively different laser intensities.
92. Repeating from step 86 with successive section planes to fabricate the component by selective layer additive manufacturing.
Inclusion of nano-scale ceramic particles can reduce the sintering temperature of the ceramic layer by as much as 350° C. in some embodiments. This can facilitate co-sintering and bonding of the metal and ceramic layers. Temperature reduction occurs particularly when the ceramic powder comprises at least 2% and up to 100% by volume of particles being less than 100 nm average diameter, and it especially occurs with particles less than 50 nm average diameter. The present method allows sintering by only partially melting such nano-particles. This is not possible when applying a ceramic coating with thermal spray technologies, because it tends to fully melt the smaller particles.
Nickel-based superalloys used in high temperature gas turbine components are often strengthened by a gamma prime precipitant phase within a gamma phase matrix. The properties of these superalloys that make them durable in high-temperature environments also make them difficult to fabricate and repair. However, they can be fabricated and joined to adjacent layers of different materials, including ceramics, by the method described herein. Casting of gas turbine blades having serpentine channels with turbulators and film cooling exit holes is difficult and expensive. The present method reduces cost while more fully joining the different material layers. It allows a complete multi-material component such as a turbine blade to be fabricated in one process, instead of casting a superalloy blade, then coating it in a separate process, such as thermal spray.
While various embodiments of the present invention have been shown and described herein, it will be obvious that such embodiments are provided by way of example only. Numerous variations, changes and substitutions may be made without departing from the invention herein. Accordingly, it is intended that the invention be limited only by the spirit and scope of the appended claims.
This application claims benefit of the 8 Oct. 2012 filing date of U.S. provisional patent application No. 61/710,995 (attorney docket 2012P24077US), and the 10 Oct. 2012 filing date of U.S. provisional patent application No. 61/711,813 (attorney docket 2012P24278US), both of which are incorporated by reference herein.
Number | Date | Country | |
---|---|---|---|
61710995 | Oct 2012 | US | |
61711813 | Oct 2012 | US |