Study on Process Optimization of Sprayable Powders and Deposition Performance of Amorphous Al2O3–YAG Coatings

Zheyi Zhang,Haifeng Yang,Yin Zhuang,Jian Rong,Yizhaotong Ai,Chuanxian Ding,Jing Sheng,Xinghua Zhong,Kai Yang

doi:10.3390/coatings10121158

Abstract

In this study, the process optimization of sprayed powders and deposition performance for amorphous Al2O3–Y3Al5O12 (YAG) coatings was investigated. The solid-state reaction mechanism of the nano-sized Al2O3 and Y2O3 powders with eutectic molar ratio was studied by multiple step-by-step heating cycle calcination processes. The calcination process could be adjusted according the dominant control factors like chemical reaction rate or ion diffusion rate. Finally, the actual deposition performance of the calcined powders (Al2O3/YAG) was examined by atmospheric plasma spraying (APS). XRD, SEM and DTA were used to characterize the powders and the as-sprayed coatings. The results showed that the reaction of Al2O3–Y2O3 system is a high temperature solid reaction dominated by Al3+ diffusion, the initial reaction process was usually belong to chemical kinetic range, then the reaction will be transformed from chemical kinetic range to diffusion dynamic range with the temperature increasing. The process optimization of powders was very effective, and the deposition effect of coating was effective.

Highlights

Y3 Al5 O12 (YAG) with garnet structure formed by the reaction of Al2 O3 and Y2 O3 is a kind of composite oxide, which is mainly used to prepare phosphors, laser crystals, etc
The nano-sized powders are light in weight and easy to agglomerate, so the fluidity of the powders is poor in the gas-solid two-phase flow of atmospheric plasma spraying
According to the current investigation results, the reaction of Al2 O3 –Y2 O3 system is a high temperature solid reaction dominated by aluminum ion diffusion, which is mainly controlled by the chemical reaction rate at the phase interfaces and the ion diffusion rate in the solid phase

Summary

Introduction

Y3 Al5 O12 (YAG) with garnet structure formed by the reaction of Al2 O3 and Y2 O3 is a kind of composite oxide, which is mainly used to prepare phosphors, laser crystals, etc. It is widely applied in the field of military, industrial and medical industries [1,2,3,4]. The as-sprayed coatings are mainly composed of amorphous phases, and some crystalline grains were distributed in the coating. This kind of coating has excellent thermo-mechanical performance. The initial crystallization temperature of the amorphous coating is as high as 876.3 ◦ C, which is much higher than that of the commonly used amorphous alloy coatings [12,13,14], such as Fe-based, Co-based and Ni-based amorphous coatings

Methods

Results

Conclusion