Papers by Author: Zeng Da Zou

Abstract: In friction surfacing process, the temperature field and strain field, especially of coating rod, is considered an important element in analyzing the process’ mechanism and choosing the key process parameters properly. In this paper, the finite element method was employed to simulate the coupling of 3-D temperature field and deformation field of coating rod during friction surfacing. The simulation results show that at the preliminary preheating period, the isotherm goes down at the center part, and the temperature field presents “M” along the radial direction. The temperature increasing rate at the friction interface is higher at first, and then become lower, once the friction system becomes quasi-steady, the temperature here will be stable approximately. The largest effective strain occurs near the center of bottom circle. The simulation results are close to the experimental results, thus builds a basis for analyzing the process’s mechanism, allows for theoretical guidance for analyzing feasibility and helps optimize key parameters.

Abstract: Friction Surfacing is an advanced surface modification method, so it is of great importance to study figuration mechanism of deposit in friction surfacing process for controlling deposit’s quality. By friction surfacing, consumable-rod of 1Cr18Ni9Ti (321)was surfaced on the substrate of mild steel (1020) by different process parameters (rotation speed, force and traverse speed). The effects of process parameters on deposit’s figuration are discussed. Experiments show that deposit’s width and thickness decrease linearly with increasing consumable-rod rotation speed; deposit’s width increases and its thickness decreases with increasing force. If traverse speed between substrate and consumable-rod increases, deposit’s thickness and width decrease simultaneously. According to conservation of mass, the material transferring & figuration rules in friction surfacing were analyzed, which explains the experimental results as well. So, figuration control methods of deposit in friction surfacing are set up. In practice, process parameters must be chosen properly to ensure good figuration. Only if process parameters are inside the feasible area, material can transfer fluently and deposit with good figuration could be got.

Abstract: Shear strength and fracture behavior of Al2O3 matrix ceramic composite brazed joints to carbon steel with Ag-Cu-Ti brazing alloy in flow argon have been studied by means of SEM, EDX and all-purpose testing machine. Results have shown that there is a close relationship between the shear strength and the fracture form of brazed joints. The fracture occurring completely in the composite near the composite/filler metal interface corresponds to the low strength of a joint, and the strength of the joint fractured partially in the composite usually increases with decreasing the proportion of the composite on the fracture surface in the steel side. When the fracture occurs in the reaction layer between the composite and the filler metal, the closer the fractured position comes to the composite/reaction layer interface, the higher the joint strength. The maximum shear strength is obtained when the fracture occurs fully at the interface.

Abstract: In this study, Si3N4 was bonded to Inconel600 with Nb/Cu/Ni interlayer by partial liquid phase diffusion bonding method under vacuum condition. The bonding temperature, bonding time, bonding pressure and cooling velocity was 1403K, 50min, 7.5MPa and 5K/min, respectively. The effects of interlayer thickness on the strength and fracture behaviors of joint were investigated through evaluating the strength of joints based on shear test and observing the fracture morphology by means of SEM. The results showed that the shear strength of joint changed with variation of the interlayer thickness. When the shear strength of joint increased, the location of fracture was changed from the ceramic/interlay interface to the reaction layer.

Abstract: WC-TiC-Co cermet and CuZnNi alloy composite coatings were produced on mild steel by a high temperature inside-furnace brazing technique. The microstructure, phase constituents and interfacial diffusion behavior of cermet and Cu-based alloy were investigated by means of scanning electron microscopy (SEM), transmission electron microscopy (TEM), electron probe microanalysis (EPMA) and X-ray diffraction. The tensile strength and wear property of composite coatings were also investigated. The results show that crème particles were not decomposed severely during the inside- furnace brazing process. The microstructure of the matrix is α and β phases. Diffusion occurred at the cermet/Cu-based alloy interface. The tensile strength of the composite coatings reached 240-300MPa, which depended on the brazing temperature and was far higher than that of the flame hardfacing layers. Cermet fracture was basically a brittle fracture in nature and matrix involves ductile fracture.