Thermal stability of the cellular structure of an austenitic alloy after selective laser melting

Published ArticleThe thermal stability of the cellular structure of an austenitic Fe–17% Cr–12% Ni–2% Mo–1% Mn–0.7% Si–0.02% C alloy produced by selective laser melting in the temperature range 20–1200°C is investigated. Metallographic analysis, transmission electron microscopy, and scanning electron microscopy show that structural changes in the alloy begin at 600-700°C and are fully completed at ~1150°C. Differential scanning calorimetry of the alloy with a cellular structure reveals three exothermic processes occurring upon annealing within the temperature ranges 450–650, 800–1000, and 1050–1200°

Pulsed laser treatment of plasma-sprayed thermal barrier coatings: effect of pulse duration and energy input

Pulsed laser treatments of plasma-sprayed thermal barrier coatings can provide good corrosion resistance of protected components without impairing thermal fatigue resistance of the ceramic layers. Laser treatments are performed over a wide range of pulse durations and energy inputs, and their effects on microstructure, crystalline grain size and chemical composition of the remelted thin upper layer are investigated. Particular attention is given to macro and microcracking originating on the surface, gas bubble motion inside the melted layer and consequent surface crater formation. Density, shape, dimension and distribution of craters in the laser-irradiated zone are correlated with pulse duration and energy input of the laser beam. A numerical simulation of temperature distributions and heat phenomena originating in the ceramic coating during laser irradiation is presented, in order to explain the influence of laser characteristics on the quality of the coating surface