煤油流量对HVOF喷涂FeCrMoSi-Ti3SiC2涂层高温摩擦磨损性能的影响

目的 提高燃煤锅炉四管的耐磨性能。方法 使用喷雾造粒技术制备FeCrMoSi/Ti3SiC2复合粉末，并利用超音速火焰喷涂技术(HVOF)在12CrMoV基体上制备煤油流量分别为26、28、30、32 L/h的复合涂层。使用X射线衍射仪(XRD)、扫描电镜(SEM)及其自带的能谱仪(EDS)、Raman、维氏显微硬度计和摩擦磨损试验机研究FeCrMoSi/Ti3SiC2粉末及其涂层相组成、组织结构，检测涂层的力学性能，并对涂层在800 ℃下的摩擦学性能和磨损机理进行系统分析。结果 粉末物相主要由Ti3SiC2、Fe-Cr和TiC组成，涂层的物相与粉末类似，但是新产生了SiC相，且随着煤油流量的升高，Ti3SiC2物相逐渐分解。当煤油流量为30、32 L/h时，涂层内Ti3SiC2物相大量分解。涂层的硬度和断裂韧性随着煤油流量的升高表现出先升高、后降低的趋势，孔隙率和磨损率呈现先减小、后增大的趋势。当煤油流量为28 L/h时，涂层磨损率最低，约为5.44 ´ 10^-15 m³/(N.m)。结论 煤油流量为28 L/h时，涂层表面生成的SiO2、TiO2和Fe2O3等氧化物均匀分布在磨痕和对偶球表面，有效阻挡了对偶球和涂层的直接接触，使得涂层显示出最优异的摩擦学性能。涂层的主要磨损机制为氧化磨损和黏着磨损。

Effect of Kerosene Flow Rate on Friction and Wear Properties of HVOF Sprayed FeCrMoSi-Ti3SiC2 Coating at High Temperature

Titanium silicon carbon (Ti3SiC2) is a new ternary compound MAX phase with excellent properties of both metallic and ceramic materials and it is prone to form oxide film on the friction surface, which makes it show excellent tribological performance at high temperature. However, the phase decomposition of Ti3SiC2-based coating prepared by thermal spraying technology is easy to occur, which affects its performance and restricts its wide application in high temperature protection filed. The work aims to individually granulate Ti3SiC2 powder by spray granulation technique, and then investigate the effect of different kerosene flow rates on the coating phase structure and tribological properties at high temperature. Ti3SiC2 particles were ground by a vertical planetary ball mill and mixed with quantitative deionized water and binder to obtain Ti3SiC2 water-based slurry, and then spherical Ti3SiC2 powder was prepared by spray granulation technique. The 12CrMoV matrix square sample with the size of 20 mm × 20 mm × 5 mm was prepared by electric discharge wire cutting mechanism. Before spraying experiment, the matrix sample was roughened by sand blasting and cleaned by ultrasonic with alcohol. The composite coatings with kerosene flow rates of 26 L/h, 28 L/h, 30 L/h and 32 L/h were prepared on 12CrMoV matrix by supersonic flame spraying (HVOF) technology. The phase composition, microstructure of powder and coating were investigated with X-ray diffractometer (XRD), scanning electron microscope (SEM), energy spectrometer (EDS) and Raman spectrum. Vickers microhardness tester and high temperature friction wear testing machine were applied to test the mechanical properties and the tribological properties. Finally, the wear mechanism of the coating at 800 ℃ was analyzed. The results indicated that the powder phase was mainly composed of Ti3SiC2, Fe-Cr and TiC. The coating phase was similar to that of the powder, but a new SiC phase appeared. With the increase of kerosene flow, the Ti3SiC2 phase was gradually decomposed. When the kerosene flow was 30 L/h and 32 L/h, the Ti3SiC2 phase in the coating was decomposed a lot. The average microhardness of K-26, K-28, K-30 and K-32 coatings was 359HV0.3, 528HV0.3, 548HV0.3 and 485HV0.3, the fracture toughness was 3.75, 3.94, 4.65 and 3.95 MPa.m1/2, and the mean friction coefficient was 0.48, 0.45, 0.59 and 0.52, respectively. The hardness, fracture toughness and average friction coefficient of the four coatings all increased firstly and then decreased with the increase of kerosene flow. The porosity of coatings K-26, K-28, K-30 and K-32 was 1.03, 0.44, 0.31 and 1.62, and the wear rates was 6.17´10-15, 5.44´10-15, 8.62´10-15 and 6.79´10-15 m3/(N.m), respectively. The porosity and wear rate of the four coatings decreased firstly and then increased with the increase of kerosene flow. In summary, when the kerosene flow rate was 28 L/h, the coating had higher MAX content, higher hardness and lower porosity, which ultimately resulted in the lowest coefficient of friction and wear rate. The K-28 coating retains a high content of MAX phase, and the oxides such as SiO2, TiO2 and Fe2O3 generated on the surface are evenly distributed on the surface of the wear scars and dual ball, effectively blocking the direct contact between the dual ball and the coating, which makes the coating show the most excellent tribological performance.