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Coupled metallographic examination and heat transfer numerical simulation are applied to reveal the laser sintering mechanisms of Ti powder of 63‐315 μm particle diameter. A Nd:YAG laser beam with a diameter of 2.7‐5.3 mm and a power of 10‐100 W is focused on a bed of loose Ti powder for 10 s in vacuum. The numerical simulation indicates that a nearly hemispherical temperature front propagates from the laser spot. In the region of α‐Ti just behind the front, heat transfer is governed by thermal radiation. The balling effect, formation of melt droplets, is not observed because the temperature increases gradually and the melt appears inside initially sintered powder which resists the surface tension of the melt.

The particularities of the selective laser processing of single‐component metal powder layers were investigated, especially the occurrence of the balling‐processes under different processing conditions. During laser processing, sintered, semi‐sintered/semi‐melted or completely melted cakes can be formed. Size and shape of the laser processed parts can change depending on the energy and time parameters of the laser irradiation and on the properties of initial powder layers.

A comparison of selective laser sintering (SLS) and selective laser cladding (SLC) methods is presented. Loose single‐component, Ni‐alloy powder was used in this study. The powder feeding system formed the flow of powder particles directed into the zone of laser spot. The particles were deposited directly onto a substrate or onto the top of a pedestal. The powders were treated with a CW‐ Nd:YAG laser (λ=1.06 μm). The beam was motionless relative to the powder bed. As a result, the samples of sintered or remelted powders were built up as the vertical rods. The geometrical characteristics, structure and mechanical properties of samples were investigated.

The normal spectral absorptance of a number of metal, ceramic and polymer powders susceptible to be utilised for selective laser sintering (SLS) technique was experimentally determined. The measurements were performed with two laser wavelengths of 1.06μm and 10.6μm obtained by using two lasers – Nd‐YAG and CO₂ respectively. The change in the powder absorptance with time during laser processing was also investigated. The effect of the absorptance characteristics on the sintering process is discussed.

A comparative characterisation of selective laser sintering (SLS) mechanisms of single‐ and two‐component powders is presented. The effects of the volume fraction of liquid phase and the powder absorptance were discussed. Single‐component Ni‐alloy, Fe and Cu powders as well as two‐component powder systems based on Ni‐alloy, Fe and Cu were investigated. In particular, the following types of two‐component powder systems were studied: Ni‐alloy‐Cu and Fe‐Cu powder mixtures as well as Cu‐coated Ni‐alloy powder and Cu‐coated Fe powders. SLS experiments were performed with a CW‐ Nd:YAG laser (λ=1.06 μm). The acting mechanism in all cases was liquid phase sintering.