Based on the central composite rotatable design (CCD), clad beads of Inconel 625 were deposited on the surface of AISI 4130 plates using hot wire pulsed TIG (tungsten inert gas arc welding) technique. The response surface methodology (RSM) was used to establish models between process parameters and geometrical characteristics of the clad beads. Then, multiple-track two-layer weld overlay was deposited using the optimized process parameters. The microstructure of the weld overlay is primarily composed of columnar dendrites, and there are also a few planar crystals and cellular dendrites near the fusion zone. Meanwhile, equiaxed grains and steering dendrites are mainly distributed in the upper portion of the weld overlay. Potentiodynamic polarization tests were used to evaluate the corrosion resistance of the weld overlay and the substrate. The results show that adding clad layers can enhance the corrosion resistance, which degrades with the increase in Fe dilution. Moreover, the corrosion resistance of the second layer surface is close to that of wrought Inconel 625.
Degradation analysis methods are increasingly used in reliability assessment of long-life products. The small sample size problem is worthy of attention in the degradation analysis. Bayesian hierarchical method is employed for fusing multi-source degradation information to handle small sample problems. The competing relationship multiple degradation models have been widely researched and applied. However, there is the non-competing multiple degradation situation exist in mechanical products. In this paper, a Bayesian hierarchical model-based information fusion degradation method with gamma process model is introduced for describing the non-competing relationship multiple degradation process. Therefore, the Bayesian method and the MCMC method are employed for parameters estimation. A numerical example of spool valve of hydraulic system in exoskeleton robot is provided to demonstrate the proposed Bayesian hierarchical model-based information fusion degradation method.
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