Design and Characterization of Additively Manufactured NGVs Operated in a Small Industrial Gas Turbine

Abstract

The use of additive manufacturing (AM), for example Selective Laser Melting (SLM), is poised to spark a revolution in the way high-temperature components for gas turbines are designed, but a number of grave uncertainties remain. These lie mainly with the materials sciences, but some questions with regard to manufacturing and operating SLM-parts as hot gas path components and the demands on the tolerances of the cooling features associated therewith remain as well. In order to quantify the impact of these uncertainties, Nozzle Guide Vanes (NGVs) with a geometry that would normally be investment-cast were produced with SLM. A back-to-back comparison of vanes from the two manufacturing processes was performed. The design of the SLM-vanes will be described and the SLMmanufacturing process of the NGVs will be touched upon, especially the use of MAR M-509, which is seldom used for SLM. In addition, characterization of the NGVs with 3D-scans of the outer geometry and the pin-fin matrix shall be discussed. The NGVs were operated for approximately 70 hours at relevant load conditions in a highly-instrumented test engine on a test bed at the Oberhausen plant of MAN. The temperatures of the AM and investment-cast vanes were measured using Thermal History Paints (THPs); a comparison between these different kinds of parts will be drawn.

Advanced Gas Turbine Cooling for the Carbon-Neutral Era

“…The heat transfer of AM pin fins increased as well, but not to such an extent that the thermal effectiveness (heat transfer per unit pressure loss) came close to that of cast ones. Other authors [116] did not see any appreciable difference in the temperature within the region with pin fins in additively manufactured and cast NGVs. This may also be attributed to the relative sparsity of the pin-fin array used.…”

“…Nonetheless, the vanes used in Ref. [116] were manufactured from MAR M-509 because they were used in direct comparison with cast NGVs, which were also made from this material. Others have investigated IN939 [109], which showed that the material parameters of the AM parts differed dramatically from cast ones or those made of IN738.…”

“…Moving away from the theoretical considerations into more practical ones, a brief overview of the application of internally cooled AM components in gas turbines is offered. Although the blades would profit most from AM designs (the vanes are already cooled well with impingement cooling), given the concerns about the material properties of AM parts, most work has been done on stationary components [109,116,[147][148][149][150]. In Ref.…”

“…In Ref. [116], additively manufactured NGVs were tested. There were considerable difficulties in printing the very thin insert for the impingement cooling, which points to the limitations with respect to the manufacturability of double-wall cooling designs, which need to be overcome.…”

In Situ Reactive Formation of Mixed Oxides in Additively Manufactured Cobalt Alloy

“…Co-base alloys such as Mar-M 509 also possess improved sulfidation resistance [ 32 ]. While in many of the hot sections of engines, where blades have been replaced with Ni-base superalloys due to the improved creep resistance mechanisms in γ/γ′ microstructures, there remains a need for carbide- and solid solution-strengthened Co alloys for stationary components such as nozzle guide vanes [ 33 ]. These components encounter high temperature exposure for long periods and applied loads are low enough that thermomechanical fatigue and surface oxidation become a more important concern [ 34 ].…”