Effect of thermal spraying parameters on cracking and thermal cycling life of thermal barrier coatings

Segmentation cracks can be formed in the top ceramic coatings of thermal barrier coating system by the thermal spraying process without any cooling. The crack system can strengthen the strain tolerance of ceramic coatings. Up to now, there are almost no systemic studies on the cracking, especially on the branch cracks. The quantitative effects of feeding rate and substrate preheating temperature were studied on the cracking in this paper. And the thermal cycling lifetimes of coatings with different cracking systems were compared. It was found that with the increase of feeding rate, the density of vertical cracks and length of branch cracks increase firstly and then decrease. The density of vertical cracks shows an increment tendency with the increase of substrate preheating temperature. However, the length of branch cracks increases firstly, and then shows a decreasing trend. It shows that the lifetime of the top ceramic coatings can be improved effectively through restraining the total length and number of branch cracks in coating and maintaining the density of segmentation cracks at a certain level.