Abstract

The aim of this study was to determine the influence of selective laser melting (SLM) process parameters on the formation of cracks in nickel-based single crystal alloy. Several sets of laser scanning parameters, with varied laser power, scanning speed and hatch distance, thus resulting in different volumetric and linear energy densities, were investigated. The relationship between energy density, specimen densification, cracks formation and evolution of directional microstructure was shown. It was found that higher linear energy density results in fewer cracking and defects. Cracking in lower energy samples was attributed to the formation of thermal shrinkage pores in the interdendritic spaces and precipitation of Ta, Mo and Nb carbides along the dendrites boundaries.

Highlights

  • Search for new materials suitable for additive manufacturing (AM) of complex parts is driving the future developments of additive technologies

  • Specimens 1 and 2 show that the integrity of the material improves with an increase in the value of the linear energy density, despite the same values of the volumetric energy density

  • This study shows the influence of various selective laser melting (SLM) process parameters on the densification and formation of cracks in Ni-based single crystal alloy

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Summary

Introduction

Search for new materials suitable for additive manufacturing (AM) of complex parts is driving the future developments of additive technologies. Nickel heat-resistant single-crystal silicon-containing alloy was developed in the second half of the last century and is usually used for the production of turbine blades using directional solidification casting method [1]. It is not possible to eliminate the release of rhenium along the borders of dendrites by heat treatment due to its low diffusive activity Such rhenium release leads to the formation of topologically densely packed phases. The advantage of the selective laser melting (SLM) over the directional solidification method is a more homogeneous distribution of alloying elements throughout the entire volume of the product, which will be discussed in this paper. The use of SLM requires optimization of process parameters and problems associated to it One of these problems is in the formation of cracks during the printing process [7-12]

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