Additive manufacturing of metallic components – Process, structure and properties

This study deals with acicular ferrite, bainite, and martensite microstructures observed in three low alloy steels. Electron backscattering diffraction (EBSD) was used to assess crystallographic features of these microstructures. In each area studied by EBSD mapping, ‘crystallographic packets’ defined as clusters of points sharing the same crystallographic orientation were compared with ‘morphological packets’ observed in the corresponding light micrograph. Microtexture studies suggested that acicular ferrite and upper bainite grow with Nishiyama– Wassermann relationships with the parent austenite phase, whereas lower bainite and martensite consist of highly intricate packets having Kurdjumov–Sachs relationships with the parent phase. In all cases three highly misoriented texture components were found within each former austenite grain. Electron backscattering diffraction also gave information about the cleavage and intergranular reverse temper embrittlement fracture mechanisms of these steels. In...

Electron backscattering diffraction study of acicular ferrite, bainite, and martensite steel microstructures

The formation of thick Ni-based coating on a steel substrate by coaxial laser cladding using the Nd:YAG 2 kW continuous laser was studied both from a theoretical and experimental point of view. The theoretical analysis concentrated on the transfer of laser irradiation and powder particles using a simple model of heat transfer to the substrate. This approach provides predictions of the laser power required for melting powder particles and substrate, respectively. For an appropriate experimental analysis of the main process parameters involved, a method based on a gradual change of a single processing parameter was examined. Correlations between the main processing parameters and geometrical characteristics of an individual laser track have been found and are discussed.

Analysis of coaxial laser cladding processing conditions

Austenite to bainite phase transformation in the heat-affected zone of a high strength low alloy steel

3-D finite element modeling of laser cladding by powder injection: effects of laser pulse shaping on the process

A model which takes into account the main phenomena occurring during the laser-cladding process is proposed. For a given laser power, beam radius, powder jet geometry, and clad height, this model evaluates two other processing parameters, namely, the laser-beam velocity and the powder feed rate. It considers the interactions between the powder particles, the laser beam, and the molten pool. The laser power reaching the surface of the workpiece is estimated and, assuming this power is used to remelt the substrate with the clad having been predeposited, the melt-pool shape is computed using a three-dimensional (3-D) analytical model, which produces mmediate results, even on personal computers. The predictions obtained with this numerical model are in good agreement with experimental results. Processing engineers may therefore use this model to choose the correct processing parameters and to establish cladding maps.

A Simple but Realistic Model for Laser Cladding

The aim of this communication is to present a calorimetric method which has been used to determine the mean absorption during the dynamic process of remelting. Under specific processing conditions where most of the laser beam impinges on the liquid pool, this technique yields the absorption value in the liquid. It can also be extended to multitrack experiments or to other laser processes, such as laser surface alloying or cladding, which is not possible with stationary methods, such as ellipsometry

A. Frenk

Papers

A Simple but Realistic Model for Laser Cladding

In-situ technique for measuring the absorption during laser surface remelting