An Investigation In Processes And Physical Properties Of Detonation Sprayed WC-Co Coatings

Detonation Spraying(DS) is an important branch in the field of thermal sprayings, because of its excellent wear resistance, corrosion resistance properties. Due to higher costs and lower productivity, DS is generally applied in the military and aerospace fields; recently it is gradually extended to the civilian direction, and has achieved good economic efficiency.The objective in this paper is to solve the defects in coating, such as higher porosity, lower hardness, and the bonding strength between matrix and coating. It makes two kinds of coatings under different conditions, and analyzes the influence of DS energy on properties of the coatings. Then it adds a mixed-N2 in the process of DS by improving the DS equipment, and further enhances the properties of the coating. In order to get the other property parameters of the coating, it measures the bonding strength between coating and the matrix in accordance with HB, tensile strength of the coating, the average coefficient of linear expansion by the indirect measurement systemy, and analyzes influence of coating on the fatigue property of matrix material.The main conclusions are as follows:1. DS energy has significant influence on the quality of coating. In a certain energy range the porosity declines and hardness increase rapidly.2. WC particles are decomposed or oxidized in the high-temperature gas, and generate W₂C or even W and amorphous organizations. The main ingredient of coating is WC and its oxidation products.3. Hardness are influenced by porosity, integration of particles and content of WC phase. The lower of porosity, the better integration of particle, the higher of the coating hardness. The content of WC phase has less impact on hardness.4. It can greatly reduce coating porosity, increase hardness by adding mixed-N2 in process of DS.5. It measures the tensile strength in accordance with HB and average coefficient of linear expansion are 113.2 MPa and 10.5±0.5×10^-6/℃respective.6. In the fatigue life experiment, the first crack appears in the coating and it develops towards matrix surface; but before the arrival, deflection occurs, and it makes coating fall off from matrix finally.