We prepared three kinds of Ni based alloy cladding coatings on 316L stainless steel at different power levels. The microstructure of the cladding layer was observed and analyzed by XRD, metallographic microscope, and SEM. The hardness of the cladding layer was measured, and the wear resistance of it was tested by a friction instrument. The results show that the effect of laser cladding is good, and it has good metallurgical bonding with the substrate. Different microstructures such as dendritic and equiaxed grains can be observed in the cladding layer. With the increase in laser power, more equiaxed and columnar dendrites can be observed. The phase composition of the cladding layer is mainly composed of γ–Ni solid solution and some intermetallic compounds such as Ni₃B, Cr₅B_3, and Ni₁₇Si₃. The results of EDS show that there are some differences in the distribution of C and Si between dendrites. The hardness of the cladding layer is about 600 HV_0.2, which is about three times of the substrate (~200 HV_0.2). Through the analysis of the wear morphology, the substrate wear is serious, there are serious shedding, mainly adhesive wear, and abrasive wear. However, the wear of the cladding layer is slight, which is abrasive wear, and there are some grooves on the surface.

In this study, single-layer and three-layer nickel-based coatings were fabricated on 316L SS by laser additive manufacturing. The phase characterization, microstructure observation, and microhardness analysis of the coatings were carried out by X-ray diffraction (XRD), scanning electron microscope (SEM), and microhardness tester. And the wear resistance of the coatings was analyzed through dry sliding friction and wear test. The results show that the cross-section microstructure of the three-layer nickel-based coating is different from that of the single-layer one under the influence of heat accumulation; the dendrite structure in the central region of the former is equiaxial dendrite, while that of the latter still remains large columnar dendrites. The existence of solid solution phase γ-(Fe, Ni) and hard phases of Ni₁₇Si₃, Cr₅B₃, Ni₃B in the coating significantly improve the wear resistance of the coating, and the microhardness is nearly 2.5 times higher than that of the substrate. However, the average microhardness of multilayer cladding coating is about 48 HV_0.2 higher than that of the single-layer cladding coating. In addition, the fine surface structure of the three-layer nickel-based coating improves the wear resistance of the coating, making this coating with the best wear resistance.

The solid particles or liquid droplets entrained by multi-phase flow in process plants can cause erosion resulting in pipe wall thinning. Hence, it is essential to evaluate erosion rate for determining design margin and taking counter-measures. Many models have been proposed for prediction of erosion induced by particles and droplets, but there is significant difference in their prediction accuracy. The present study aims at verifying prediction accuracy of some major erosion models using the published experimental data, for engineering applications. CFD benchmark simulations were conducted for different flow velocities and piping geometries to investigate prediction accuracy of particle-induced erosion rates for five major erosion models, using the experimental data in literature. CFD results show that the erosion rates predicted by Grant and Tabakoff model are closest to the experimental results with acceptable prediction accuracy for engineering applications. At the same time, CFD benchmark simulations were also carried out to verify the prediction accuracy of droplet induced erosion rates for three erosion models, using the published experimental data. CFD results show that the erosion rates predicted by Haugen model for all the water impingement velocities are closest to the experimental results with acceptable prediction accuracy for engineering applications.

Prevention of piping vibrations during design stage has attracted attention recent years. Though the piping vibration occurs due to various mechanisms, the vibration due to fluid turbulence is one of a major topic discussed. The pressure fluctuation due to fluid turbulence occurs around flow discontinuities such as branches, elbows, flow expansions and valves, and the fluctuation can cause the piping vibration and both shell mode and beam mode vibration can occur. Guideline published by Energy Institute UK[1] (EI-AVIFF) shows a method to check the possibility of piping vibration due to flow induced turbulence and it gives some information on recommended piping span. The method is quite useful for screening purpose to select the piping system with potential vibration risks. However, it is known that the guideline is based on very conservative assumptions, as 90-degree miter bend, and it results in overdesign of piping systems, so more detailed vibration assessment approach succeeding the screening is demanded. In this paper, the method of detailed beam-mode piping vibration assessment using finite element dynamic structural analysis and Large Eddy Simulation (LES) based CFD are discussed. As an example, LES based CFD analyses were conducted on 90 degrees single miter bend, long and short elbow. The resultant pressure fluctuations are compared to past published report and good agreement was confirmed. The CFD results were reorganized and piping dynamic analysis were conducted. Based on these analysis results, the detailed piping vibration risk assessment method using CFD and dynamic structural analysis are proposed.

Three kinds of Ni based alloy cladding coatings were prepared on 316L stainless steel at different power. The microstructure of the cladding layer was observed and analyzed by XRD, metallographic microscope and SEM. The hardness of the cladding layer was measured, and the wear resistance of the cladding layer was tested by friction instrument. The results show that the effect of laser cladding is good and the cladding layer has a good metallurgical bonding with the substrate. Different microstructures such as dendritic and equiaxed grains can be observed in the cladding layer. With the increase of laser power, more equiaxed and columnar dendrites can be observed. The phase composition of the cladding layer is mainly composed of γ - Ni solid solution and some intermetallic compounds such as Ni3B, Cr5B3 and Ni17Si3. The results of EDS show that there are some differences in the distribution of C and Si between dendrites. The hardness of the cladding layer is about 600 HV0.2, which is about three times of the substrate (~ 200 HV0.2). Through the analysis of the wear morphology, the substrate wear is serious, there are serious shedding, mainly adhesive wear and abrasive wear. However, the wear of cladding layer is slight, which is abrasive wear, and there are some grooves on the surface.