Research on flame characteristics and coating growth process of titanium alloy in HVAF spraying

Abstract

In this work, a flow field model of WC–12Co powder sprayed by high-velocity air fuel (HVAF) was established based on the computational fluid dynamics (CFD) method. The macro–micro coupled thermodynamic model of coating multilayer growth process was established based on the birth and death element method. The temperature and velocity of the particles in the combustion flame were applied to the coating growth model, and the transient evolution of the coating temperature and thermal stress was revealed. The results show the temperature and thermal stress of coatings increase with the increasing the number of spraying layers, and their incremental gradient gradually decreases with the increasing the number of deposition layers. The peak temperature of the coating surface reaches 1494 K, and the peak thermal stress of the first coating reaches 2693 MPa. The maximum stress of spraying particles appears at the contact edge of particles. Further preparation of WC coating, through the hardness, friction, and wear, corrosion tests verify that WC–12Co coating can effectively provide the TC18 substrate performance. The microhardness of WC–12Co coating was approximately three times that of TC18 substrate. The average friction coefficient and corrosion rate of the coating are 0.15 and 0.06 mg/cm²/h lower than that of the substrate, respectively.