Search

The residual stress distributions of ZrO 2 /NiCoCrAlY high-temperature coatings were analyzed using an analytical model and finite element analysis. Three different topics were involved, namely the effect of interlayer on the stress distribution, the zero-deflection design for typical duplex-layer thermal barrier coating-based system, and the edge effect on the residual stress distribution. These topics could provide some insights into the development of a fail-safe design methodology for high-temperature coating systems.

The microstructure and the mechanical properties of the electro-thermal explosion directionally sprayed molybdenum coatings were determined by means of SEM, XRD and microhardness tester, respectively. Experiments on the tribological property of the coatings were performed using a ring-on-block type wear tester. Results showed that the molybdenum coatings were characterized by compact microstructure, high bonding strength and high wear resistance. The applied loads and the counterpart's hardness have an obvious influence on the tribological properties of the coatings. Several wear failure modes, such as micro-plowing and pits, were identified in the post-testing analysis.

In this work, the microstructure and sliding wear behaviors of stainless steel (AISI 420) coatings prepared by electro-thermal explosion directional spraying (EEDS) and high velocity arc spraying (HVAS) were comparatively investigated. Results show that the EEDS coatings possess more compact microstructure, higher nano-hardness and nano-elastic modulus, finer bond and better wear resistance than the HVAS coatings. The dominant wear mechanism of EEDS coatings is slight furrow and that of HVAS coatings is serious furrow and delamination.

A three-dimensional clasto-plastic finite element analysis of pre-twist process for a torsional axis made of 45GrNiMoVA steel, was carried out using a commercial finite element analysis code, MSC MARC 2001. The results show that the critical pre-twist strain angle is 0.027 rad and the maximum elastic shear stress after pre-twist is 1 694 MPa for the torsional axis.

In manual brush-plating process, the coating quality is assured by the experience of the operator. The operator continuously regulates the plating voltage, the speed of the work piece, and the moving speed of the stylus handle according to the plating state he is watching. While in automatic brush-plating process the parameters above are also needed to adjust automatically so as to obtain coating with high quality and, to meet the requirement of piece dimension. However on this occasion the difficult is how to convert the experience of the operator into the suitable control algorithms of the machine. In order to achieve this purpose, a fuzzy controller has been developed, which adopts the coating thickness, the solution temperature, the plating current density, and the deposit rate as input variables, while the relative speed between stylus handle and work piece, the plating voltage, the longitudinal moving speed of stylus handle, and the flux of solution as output ones. The controller has been applied to an automatic brush-plating machine, and the experimental results are satisfactory and help certify this method’s applicability.

Remanufacturing in China is still in its early stage and faces pressures from society, policy, technology and management. Considering the current state of remanufacturing in China, this paper researched several key management issues involving various aspects from the perspective of remanufacturing players. Based on a needs analysis on the trend of remanufacturing development in China, the following six key management problems were researched; risk management of remanufacturing players, remanufacturing production management, remanufacturing quality management, authentication mode of remanufactur- ing in China, subsidy policy of remanufacturing industry, and performance assessment of remanufacturing. The characteristics of issues were analyzed and the correspond- ing countermeasures were put forward.

A Cr3C2–NiCr coating with a thickness of 200 μm was deposited on an AISI 1045 steel substrate using a supersonic plasma-spray technique. The hardness of the Cr3C2–NiCr coating was characterized by a nano-indenter equipped with an atomic force microscope (AFM). The AFM images indicated that the nano-indents on the Cr3C2–NiCr coating exhibited significant “pile-up” deformation. Such pile-up behavior needs to be taken into account in hardness determination because the pile-up height accounts for a large proportion of the indentation depth. In this paper, four different methods are compared to determine the hardness of the Cr3C2–NiCr coating: the Oliver–Pharr method, two work-of-indentation methods (total work of indentation and plastic work of indentation), and an AFM analysis method. The results show that the Oliver–Pharr and work-of-indentation methods overestimated the hardness, and the AFM analysis method is considered as a more accurate method for determining the hardness of the Cr3C2–NiCr coating.