Showing papers by "Robert F. Singer published in 2018"
TL;DR: In this paper, selective electron beam melting (SEBM) is shown to be a viable production route for titanium aluminides components and fully dense and crack free parts can be produced.
Abstract: Selective electron beam melting (SEBM) is shown to be a viable production route for titanium aluminides components. Fully dense and crack free parts can be produced. In the present paper a titanium aluminide alloy Ti-45Al-4Nb-C was investigated and the complete processing chain was developed, i.e. starting from the determination of the processing window, the evaluation of corresponding material properties for cube like specimens and finally the production of turbocharger wheels. The material properties were optimized by adjusting scanning strategy as well as heat treatment with particular consideration of the application to turbocharger wheels. The issue of dimensional accuracy and the feasibility of joining will be discussed and a proof test is performed.
74 citations
TL;DR: In this article, Alloy solid solution strengthening elements were added in graded amounts, and measured the solidus, liquidus, and γ′-solvus temperatures of the samples by DSC.
Abstract: We prepared 41 different superalloy compositions by an arc melting, casting, and heat treatment process. Alloy solid solution strengthening elements were added in graded amounts, and we measured the solidus, liquidus, and γ′-solvus temperatures of the samples by DSC. The γ′-phase fraction increased as the W, Mo, and Re contents were increased, and W showed the most pronounced effect. Ru decreased the γ′-phase fraction. Melting temperatures (i.e., solidus and liquidus) were increased by addition of Re, W, and Ru (the effect increased in that order). Addition of Mo decreased the melting temperature. W was effective as a strengthening element because it acted as a solid solution strengthener and increased the fraction of fine γ′-precipitates, thus improving precipitation strengthening. Experimentally determined values were compared with calculated values based on the CALPHAD software tools Thermo-Calc (databases: TTNI8 and TCNI6) and MatCalc (database ME-NI). The ME-NI database, which was specially adapted to the present investigation, showed good agreement. TTNI8 also showed good results. The TCNI6 database is suitable for computational design of complex nickel-based superalloys. However, a large deviation remained between the experiment results and calculations based on this database. It also erroneously predicted γ′-phase separations and failed to describe the Ru-effect on transition temperatures.
22 citations
TL;DR: In this paper, an improved numerical multi-criteria optimization tool using CALPHAD calculations and semi-empirical models for alloy development is presented and a possible phase stability model extending the optimization tool and improving the alloy composition predictions is presented.
Abstract: The development of new Ni-base superalloys with a complex composition consisting of eight or more alloying elements is a challenging task. The experimental state-of-the-art development cycle is based on the adaption of already existing compositions. Although new alloy compositions with potentially improved material properties are expected to be similar to already known superalloys, this procedure impedes efficiently finding these compositions in the large multi-dimensional design-space of all alloying elements. Modern alloy development combines numerical optimization methods with experimental validation to guide the development towards promising compositions. In this work, an improved numerical multi-criteria optimization tool using CALPHAD calculations and semi-empirical models for alloy development is presented. The model improvements to its predecessor are described and the successful application for the development of rhenium-free single-crystal Ni-base superalloys ERBO/13 and ERBO/15 is revisited. The optimization tool is described and the designed alloys are discussed regarding phase stability. Finally, a possible phase stability model extending the optimization tool and improving the alloy composition predictions is presented.
16 citations
Patent•
26 Jul 2018
TL;DR: In this article, a continuous extrusion process for a metal-containing bulk material (13) for producing an extruded body, comprising the following steps: introducing the metal containing bulk material into a press channel (8), which is bounded by a rotating extrusion wheel (2) and pressing tool components, which comprise a running-in region having sealing plates (5, 6, 7) and comprise a deflecting region with a counter plate (11) and a feeding plate (10), feeding in the metal-contained bulk material via a peripheral groove (3) of the rotating
Abstract: Continuous extrusion process for a metal-containing bulk material (13) for producing an extruded body, comprising the following steps: introducing the metal-containing bulk material (13) into a press channel (8) of a metal-powder extrusion installation (1), which is bounded by a rotating extrusion wheel (2) and pressing tool components, which comprise a running-in region having sealing plates (5, 6, 7) and comprise a deflecting region with a counter plate (11) and a feeding plate (10), feeding in the metal-containing bulk material (13) via a peripheral groove (3) of the rotating extrusion wheel (2) to the counter plate (11) and deflecting the compacted metal-containing bulk material (13) in the deflecting region through the feed plate (10), which has an opening, to a die (12), wherein at least one of the sealing plates (5, 6, 7) arranged in the running-in region is cooled by means of a cooling device. The invention also relates to a metal-powder extrusion installation that is suitable for carrying out the extrusion process according to the invention.