Cheng Meng

Bio: Cheng Meng is an academic researcher. The author has contributed to research in topics: Composite material & Materials science. The author has co-authored 2 publications.

Effect of High-Temperature-Assisted Ultrasonic Deep Rolling on Microstructure and Tribological Properties of Ni-WC Coatings

Abstract: Cermet coatings are post-treated by a new surface microcrystallization technology, namely high-temperature-assisted ultrasonic deep rolling (HT + UDR). The process parameters of ultrasonic deep rolling significantly affect the microstructure and tribological properties of the Ni-WC coatings. In this paper, the samples were treated with different preloading depths (0.20 mm, 0.25 mm, and 0.30 mm), and the microstructure and properties of the coatings were characterized by SEM, EDS, X-ray stress analysis, and micro-Vickers hardness testing. An MMW-1A-type friction and wear tester was used for the dry friction and wear test at room temperature, respectively. Compared with the untreated sample, plastic rheology occurred on the surface of the coatings after HT + UDR, showing a phenomenon of “cutting peaks and filling valleys”. In the treated coatings, visible cracks were eliminated, and the inside of the coating was denser. The surface hard phase was increased as a “skeleton” and embedded with the soft phase, which played a role in strong and tough bonding. After HT + UDR + 0.25 mm treatment, the surface roughness increased by 68%, the microhardness of the surface layer reached a maximum of 726.3 HV0.1, and the residual tensile stress changed from 165.5 MPa to −337.9 MPa, which inhibited the germination and propagation of cracks. HT + UDR improved the wear resistance of the coating in many aspects. The coating after the 0.25 mm preloading depth treatment possessed the smallest friction coefficient and the lowest wear amount, which is 0.04 and 4.5 mg, respectively. The wear form was abrasive wear, and the comprehensive tribological performance is the best.

Effect of Different Si Target Currents on Performance of Magnetron Sputtering Wear Resistant Coatings

Abstract: In order to ameliorate the properties of the coating material on the surface of the key moving parts of artillery, the influence of different Si target currents on microstructure and mechanical performances of magnetron sputtering TiAlMoSiN coating was studied. The phase structure of the coating, microstructure, coating adhesion, friction and wear properties were characterized, respectively. The deposited TiAlMoSiN coatings were mainly composed of TiN phase, Mo2N phase, amorphous Si3N4 phase and amorphous AlN phase. A typical columnar nano-multilayer structure was formed on the TiAlMoSiN coating after magnetron sputtering process. When the Si target current reached 1.0A, the coating hardness was supreme, valued 32.6 GPa. Along with the addition of the Si target current, the hardness and the bonding strength between the coatings and 45 steel substrates declined. As the Si target current was 1.5 A, TiAlMoSiN coating has the lowest friction coefficient and wear rate. Moreover, it was found out the coating with Si target current at 1.0A had shown the optimal surface properties.