AI
Thursday, September 29, 2016 3:02:39 PM
re: The proverbial devil in the details
There's a devil there alright and dealing with a devil always comes with problems. I have lots of questions. That could be a grain boundary between seed induced microstructure and pre-existing grain structure in the part, so the microstructure is intended to be global, not local, with respect to the part. Then the finished part will eventually have the microstructure on the left side. Notice that the microstructure on the left seems to have what is for some applications a very desirable Widmanstätten pattern. It may be, given that the Y direction in FIG. 1 is parallel to a crystallographic orientation, that we're talking about homogeneous vertical layers, but when looking at a horizontal slice, we see bands or other patterns.
There's a maddening kind of vagueness in that first boldface sentence following [0057], the last paragraph below. Do they mean you can specify a microstructure for the entire part or that the microstructure can vary within the part? I'm not sure.
Then I look to the 2nd boldface sentence in which they use the phrase "without limitation." That could mean there's no limit on how local, or how global, in the way I read it.
Regardless, if we interpret this to say that the range of microstructures possible with the EBM is from single crystal to fine grained as a global quality in the same part, (i.e. the entire part is a single grain or the entire part is fine grained and not both) and that that can be determined from different processes for a given alloy, that's more than I know is possible with SLM. If this is indeed location specific microstructure, EBM has 4th dimension capabilities in 3d printing that SLM can only dream about, for now.
[0057] The process of the invention may be used to produce superalloy metal materials and articles having a crystal microstructure which varies from highly textured to single crystal textured. The crystal microstructure can be controlled by the inclusion of one or more seed crystals having a single crystal orientation. Crystal orientations are referred to, in general, by their Miller Index. The crystal orientation of the seed crystal may be such that Y direction shown in FIG. 1 is parallel with any of the following crystallographic orientations, without limitation, <100>, <010>, <001>, <110>, <011>, <101>, <-110>, <0-11>, <-101>, <111>, <-111>, <1-11>, <11-1>, <102>, <-102>, or <200>. Thus, the resulting superalloy metal will have a microstructure orientation such that the part growth direction is parallel with one of the following crystallographic orientations, without limitation, of <100>, <010>, <001>, <110>, <011>, <101>, <-110>, <0-11>, <-101>, <111>, <-111>, <1-11>, <11-1>, <102>, <-102>, or <200>. In certain embodiments, the seed crystal may be provided in the form of a single crystal superalloy plate upon which the metal is formed during the processing step.
There's a devil there alright and dealing with a devil always comes with problems. I have lots of questions. That could be a grain boundary between seed induced microstructure and pre-existing grain structure in the part, so the microstructure is intended to be global, not local, with respect to the part. Then the finished part will eventually have the microstructure on the left side. Notice that the microstructure on the left seems to have what is for some applications a very desirable Widmanstätten pattern. It may be, given that the Y direction in FIG. 1 is parallel to a crystallographic orientation, that we're talking about homogeneous vertical layers, but when looking at a horizontal slice, we see bands or other patterns.
There's a maddening kind of vagueness in that first boldface sentence following [0057], the last paragraph below. Do they mean you can specify a microstructure for the entire part or that the microstructure can vary within the part? I'm not sure.
Then I look to the 2nd boldface sentence in which they use the phrase "without limitation." That could mean there's no limit on how local, or how global, in the way I read it.
Regardless, if we interpret this to say that the range of microstructures possible with the EBM is from single crystal to fine grained as a global quality in the same part, (i.e. the entire part is a single grain or the entire part is fine grained and not both) and that that can be determined from different processes for a given alloy, that's more than I know is possible with SLM. If this is indeed location specific microstructure, EBM has 4th dimension capabilities in 3d printing that SLM can only dream about, for now.
[0057] The process of the invention may be used to produce superalloy metal materials and articles having a crystal microstructure which varies from highly textured to single crystal textured. The crystal microstructure can be controlled by the inclusion of one or more seed crystals having a single crystal orientation. Crystal orientations are referred to, in general, by their Miller Index. The crystal orientation of the seed crystal may be such that Y direction shown in FIG. 1 is parallel with any of the following crystallographic orientations, without limitation, <100>, <010>, <001>, <110>, <011>, <101>, <-110>, <0-11>, <-101>, <111>, <-111>, <1-11>, <11-1>, <102>, <-102>, or <200>. Thus, the resulting superalloy metal will have a microstructure orientation such that the part growth direction is parallel with one of the following crystallographic orientations, without limitation, of <100>, <010>, <001>, <110>, <011>, <101>, <-110>, <0-11>, <-101>, <111>, <-111>, <1-11>, <11-1>, <102>, <-102>, or <200>. In certain embodiments, the seed crystal may be provided in the form of a single crystal superalloy plate upon which the metal is formed during the processing step.
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