Doctoral thesis information of PhD candidate Bui Van Khoan (revised version after the Institute-level Council):

Full name of PhD candidate: Bui Van Khoan

Affiliation: Hung Yen University of Technology and Education

Supervisors: Assoc. Prof. Dr. Le Thu Quy, Dr. Phan Thach Ho

Field: Mechanical Engineering – Code: 9520103

Training institution: National Research Institute of Mechanical Engineering – Ministry of Industry and Trade

Thesis title: "Study on the influence of plasma spray coating technological parameters on the properties of Al2O3-TiO2 ceramic coating on steel substrate"

Summary of new conclusions of the thesis

1. Based on the experimental conditions at the training institution, the influence of three plasma spray parameters on coating quality, including spray current (I), spray distance (L), and powder feed rate (M), was selected and studied in depth. Microhardness, bond strength, porosity, and friction coefficient are important property indicators of the coating that have been evaluated and analyzed.

2. Using the Taguchi method combined with ANOVA analysis, the percentage influence of the three spray technological parameters on the output quality indicators was determined. The thesis established single-objective optimal spray parameter sets to achieve the highest hardness (619.54 HV); the lowest friction coefficient (0.49); the highest shear bond strength (60.52 MPa); and the lowest porosity (3.92%).

3. Using the least squares method, second-order empirical regression function equations were developed to express the relationship between hardness, bond strength, porosity, and friction coefficient of the coating with the three spray technological parameters I-L-M for predicting coating quality.

4. Through the Overall Evaluation Criterion (OEC), the optimal spray parameter set (I = 600 A; L = 110 mm; M = 1.9 kg/h) was determined, simultaneously ensuring three output mechanical properties of the coating (hardness 585.6 HV; shear bond strength 56.4 MPa; porosity 4.24%), with deviations from the single-objective optimal results at a low level (< 10%).

5. Both single-objective and multi-objective optimization results show that among the three spray technological parameters I-L-M, the spray current always has the greatest influence on the coating quality indicators, significantly greater than the other two parameters. XRD analysis results determining the phase composition of the coating samples compared to the initial spray powder phase composition show that, depending on the spray regime, under the effect of plasma energy, phase transformation occurred with the formation of some new phases when the spray current increased, such as γ-Al2O3 (transformed from α-Al2O3), rutile-TiO2 (transformed from anatase-TiO2), Al2TiO5 (combination of Al2O3 and TiO2).

Detailed information of the doctoral thesis of PhD candidate Bui Van Khoan:
->For the full text of the thesis, please click here
->For the Vietnamese abstract of the doctoral thesis, click here
->For the Vietnamese summary of the doctoral thesis, click here
->For the English summary of the doctoral thesis, click here
->For the doctoral thesis information in Vietnamese, click here
->For the doctoral thesis information in English, click here