Influence of deposition parameters on the formation of surface cracks in segmented APS-TBCs

Segmented structure featuring channeled surface cracks has been identified as a highly exceptional type of air plasma spray (APS) thermal barrier coating system (TBCs) with remarkable strain tolerance and long-term serviceability. However, the underlying mechanisms governing the relationship between deposition parameters and segmental cracking responsible for surface crack formation in APS-TBCs remain incompletely elucidated. In this article, we conducted experimental analysis to investigate the sensitivity of five chosen deposition parameters on the induced peak quenching stress in top coat (TC) during fabrication. Subsequently, we established a quantitative relationship between the five deposition parameters and the peak quenching stress, enhancing our understanding of how these parameters influence segmental cracking. During our investigation, we monitored in-flight particle parameters using the DVP-2000 equipment and coating mechanical parameters using a self-developed real-time curvature measurement equipment under different deposition conditions. This allowed us to further analyze the correlations between particle and coating parameters. Based on their relative impact on peak quenching stress, we determined that the sensitivity of these five deposition parameters on segmental cracking is as follows: deposition power > deposition speed > preheating cycles > deposition distance > feed rate. Furthermore, we recommend setting optimum deposition parameters as follows: highest power, lowest speed, highest preheating cycles, lowest distance, and lowest feed rate to improve the possibility of fabricating segmented APS-TBCs with higher density of surface cracks.