This study is to determine the adhesion strength characteristics of the coating layer created inside cylindrical surfaces using high velocity oxygen fuel (HVOF) technology. The coating material is tungsten carbide powder on a 20 Cr steel substrate. The main parameters of the spraying process studied include spray flow, spray distance, and relative velocity of the spray gun. The experiments are arranged according to Taguchi L9 design. The research results show that the selected spraying process parameters in the experiment significantly affect the adhesion strength of the coating to the substrate. According to Taguchi and Anova analysis in the experiment, the optimal spray parameter values are achieved at a spray distance of 0.25 m, powder flow of 26 g/minute, and relative velocity of the spray gun at 0.15 m/s. With these parameters, the optimal adhesion strength value obtained is 66.47 MPa. The analysis results also indicate the influence of the spraying process parameters on adhesion strength, with spray distance contributing 38.4%, powder flow 34.7%, and spray gun velocity 25.7%. A math function was developed to establish the relationships between adhesion strength and spraying parameters, enabling the evaluation of the influence of the researched spraying parameters on adhesion.