On the delamination and crack formation in a thin wall fabricated using laser solid freeform fabrication process: An experimental–numerical investigation

The effect of localized dynamic surface preheating in laser cladding of Stellite 1

“…It was shown by a proper set of operating parameters; a well-developed melt pool can effectively improve poor bonding, and consequently reduce potential delamination between deposited tracks and the substrate. However, even under a proper set of operating parameters micro and macro cracks can be formed even for well-behaved materials in the cladding process, specifically in multi-material deposition due to the differences in the thermal expansion coefficients of the used materials [19,27]. The relationship between the thermal strain/stress and temperature gradient, defined based on the thermoelastic constitutive equations [29], indicates that by controlling the thermal gradient throughout the deposition process, it is possible to control the contraction caused by the thermal strains, and accordingly thermal stresses.…”

“…Micro-cracks substantially decreased across the wall for the samples preheated over 600 K. A crack-free wall was fabricated using the substrate preheated to 800 K prior to the fabrication process. For the fabrication of the wall, the process speed and laser power were set to 1.5 mm/s and 300 W, respectively [19]. However, it was reported that in the second layer of Stellite SF6, micro-cracks were observed.…”

“…This ultimately facilitates to manage the thermal stresses and thus the delamination and crack formation [13][14][15][16][17]. For instance, the effect of preheating the substrate to manage the thermal stresses was studied using the numerical models [15,18,19]. In these studies, the whole substrate was preheated in advance and corresponding temperature of the substrate was considered as an initial condition for the simulation of the process.…”

Cracking behavior and control of Rene 104 superalloy produced by direct laser fabrication

“…Certainly, there is no heat affected when the distance from laser source to this position is far enough. Such a specific thermal condition makes the DLF process sensitive to cracking, as reported by Alimardani et al (2009) and Hussein et al (2013).…”

Effect of heat input on cracking in laser solid formed DZ4125 superalloy

“…When the thermal stresses exceed the critical value, the cracks occur as the results of the undrawn liquid films [13,23]. The low heat input leads to the less amount of liquid during laser processing, but the effect of the higher thermal stresses caused by the high temperature gradient become significant [24,25]. On the contrary, even though the high heat input causes the thicker liquid film, the occurrence of the cracking could be unnecessary with the release of thermal stresses at the low temperature gradient.…”