# Study on Preparation of Aluminum Ash Coating Based on Plasma Spray
## 2 Experiments
### Characterization and Test  
The coating was prepared by the plasma spraying complete set of equipment, namely the FH-80 type, produced by China Shanghai Fahan Spraying Machinery Co., Ltd. The composition analysis was performed by X-ray fluorescence (XRF), which is the MiniPal4 type, produced by PANalytical Company. Phase analysis was performed by X-ray diffraction (XRD) analysis, the D/Max 2500 PC Rigaku type, produced by Japan Science and Technology Co., Ltd. The microstructure of the coating was observed by scanning electron microscope (SEM), S-3400 type, produced by Hitachi, Ltd. Adhesive strength was tested by the mechanical test machine, CMT5105 type, produced by MTS Industrial Systems (China) Co., Ltd. Abrasion rate was measured by ring three-body abrasion tester, MMH-5 type, Jinan Hansen Precision Instrument Co., Ltd. The microhardness was measured by a digital microhardness tester, TMV-1 type, which was produced by Times Group. The porosity was measured by the Archimedes drainage method, and the experimental platform was self-made.  
The diffraction pattern was obtained by Jade 6.0 and Orgin 9.1 analysis software. The flow properties of the USP were evaluated by the angle of repose, and it refers to GB/T11986-1989 \"Measurement of surfactant powder and particle angle of repose\". The adhesive strength of the coating refers to GB/T8642-2002 \"Thermal spray-determination of adhesive bond strength\".  
The main parameters used to evaluate the performance of ultimate coating were porosity, adhesive strength, microhardness, and abrasion rate. According to the work of [23], the porosity can be measured by multiple methods, such as liquid intrusion, nondestructive testing, and image microscopic analysis. When the thermal spray method a is detonation gun, the porosity level is below 1%. However, in this experiment, we proposed a method for characterizing porosity from the side using water absorption. It is a simplified Archimedes drainage method, which is easy to operate, and the experimental results are convenient for calculation. The test piece of the coating was dried and weighed to obtain a mass m\({}_{0}\), and then put in distilled water to get the mass of the discharged water m\({}_{1}\). The test piece was removed from the water and weighed to obtain the mass m\({}_{2}\). Finally, the porosity of the ultimate coating could be obtained according to the formula \((m_{2}-m_{0})/m_{1}\). It can be seen from the formula that this method is different from the traditional porosity calculation method, so there are some differences in the calculation results. This method can qualitatively reflect the change trend of porosity; that is, the smaller the measured value, the denser the coating, which provides a basis for the optimization of spraying process parameters. According to the China national standard GB/T 8642-2002, the adhesive strength was measured by the stretching method. The equipment used was a universal mechanical testing machine, CMT5105 type, produced by Meters Industrial Systems (China) Co., Ltd. Owing to the thin thickness of the aluminum ash coating, the Vickers hardness tester was used to measure the hardness of ultimate coating. The 10 relatively smooth areas selected on the surface of the coating were tested and the results were averaged. Sandpaper was used as the grinding part to test the abrasion rate of the ultimate coating. The sample after abrasion was ultrasonically cleaned, dried, and weighed, and the abrasion rate was calculated according to the formula \((m_{1}-m_{2})/t\), where \(m_{1}\) is the mass before grinding, \(m_{2}\) is the mass after grinding, and \(t\) is the grinding time.  
Figure 4: Process flow of the ultimate coating preparation.