Search

The present paper addresses the phenomena of hot cracking of nickel-based superalloys in the perspective of hybrid Laser Metal Deposition (combined application of induction and laser). This includes an extract of relevant theoretical considerations and the deduction of the tailored approach which interlinks material–scientific aspects with state-of-the-art manufacturing engineering. The experimental part reflects the entire process chain covering the manufacturing strategy, important process parameters, the profound analysis of the used materials, the gradual process development, and the corresponding hybrid manufacture of parts. Furthermore, hot isostatic pressing and thermal treatment are addressed as well as tensile testing at elevated temperatures. Further investigations include X-ray CT measurements, electron backscattered diffraction (EBSD), and scanning electron microscopy (SEM) as well as light optical microscope evaluation. The fundamental results prove the reliable processibility of the high-performance alloys Mar-M-247 and Alloy 247 LC and describe in detail the process inherent microstructure. This includes the grain size and orientation as well as the investigation of size, shape, and distribution of the γ′ precipitates and carbides. Based on these findings, the manufacturing of more complex demonstrator parts with representative dimensions is addressed as well. This includes the selection of a typical application, the transfer of the strategy, as well as the proof of concept.

To improve the oxidation resistance of a third generation Ti–Al alloy (TNM-B1) at high temperatures, aluminium rich coatings were deposited using pack cementation and magnetron sputtering. The coatings formed were analysed and compared with respect to phases formed and the containing elements. Oxidation tests were carried out on the additionally fluorine treated and preoxidised samples at 900 C in air. Compared to uncoated samples the beneficial effect of coating deposition was confirmed. Additionally, the concentration of incorporated oxygen in the subsurface zone and its influence on the mechanical properties were investigated using EPMA and microhardness measurements. Oxygen concentrations were determined for the three phases of the substrate material -TiAl, -TiAl, and -Ti(Al), and depended on the previous coating layer deposition.

A major part of additive manufacturing focuses on the fabrication of metallic parts in different fields of applications. Examples include components for jet engines and turbines and also implants i ...

Laser metal deposition has been already introduced in various industrial branches, as aviation, energy, medical technology, or tooling. Depending on process conditions of the specific application, powder, wire, or even strips can be used as filler material to coat, and to refurbish as well as to manufacture parts and functional components. Independent from the chosen type of filler material, the deposition has to be in line with specific requirements such as the allowed appearance of porosity, delamination, dilution, or cracking. The latter often becomes rather challenging due to high thermal gradients caused by typical laser-related high energy densities. Relief can be found by hybrid processing as well as suited process regimes yielding in suitable tailored temperature states and crack-free material deposition. Within this paper, such tailored solutions for the manufacturing and processing of materials with a high hot and cold cracking susceptibility such as nickel-based superalloys and alloys based on titanium aluminides are presented. Critical impacts like heating and cooling based on the analysis of melt pool flow and the morphology of solidification are considered. The authors present possibilities to influence, control, and monitor the process. The mechanical properties of corresponding additive manufactured demonstrators will be validated on the basis of destructive and nondestructive testing.

In order to lead to a competitive advantage, there is the need to carefully consider the pros and cons of state-of-the-art manufacturing techniques. This is frequently carried out in a competitive ...