Influence of Laser Energy Density on Interfacial Diffusion Bonding and Surface Density of Chromium Coating by Multi-Arc Ion Plating on Zirconium Alloy

Abstract

The chromium coating prepared by multi-arc ion plating on the surface of zirconium alloy is easy to fall off under extremely harsh conditions due to the defects of larger particles, pores and weak adhesion between the coating and the zirconium alloy substrate. Here we apply a new composite process for the fabrication of Cr coating by laser melting multi-arc ion plating technology. The numerical model of temperature field laser melting treatment was established, and based on the analysis of the above temperature field of laser melting treatment, the laser with an energy density of 9 × 104 J/cm2–18 × 104 J/cm2 was selected as the heat source. Laser energy density has a great influence on the diffusion behavior of Cr at the coating-substrate interface. When the energy density of laser is 9 × 104 J/cm2, the laser heat source cannot provide enough energy to melt the surface of the coating, however, the Cr element diffuses slightly at the membrane base interface, forming a Cr diffusion zone of about 4 μm. When the energy density of the laser increases to 13.5 × 104 J/cm2, the Zr element of the substrate diffused to the whole Cr coating, and the original Cr coating disappeared, forming a Zr-Cr diffusion and fusion zone of 30 μm. As the laser preparation process of the coating is a mixed sintering process of liquid phase sintering and solid phase sintering, the coating surface forms a dense zone and a loose zone respectively, resulting in the increase of porosity and particle rate. With the laser energy density increasing gradually, the Zr-Cr fusion zone is formed, and the coating surface particles were gradually refined and the pores were significantly reduced. With the further increase of laser energy density of 18 × 104 J/cm2, the Zr-Cr fusion zone was extended to 60 μm, and the porosity and particle rate were reduced to 0.3% and 0.4% respectively. In addition, the original stratification cracking of the film base at the fracture of the tensile specimen disappears, and the protrusion of the interface is formed. Coatings with dimple fractures were found, which indicates that the coating exhibited ductility and interfacial metallurgical bonding.

Process Optimization and Tailored Mechanical Properties of a Nuclear Zr-4 Alloy Fabricated via Laser Powder Bed Fusion

“…The melt pools become stable under a moderate laser power. A further increase in the scanning speed under a low laser power leads to insufficient energy within the melt pools, resulting in the increase of unmelted powder particles and pores, thus exhibiting a decreasing trend of the relative density [ 32 , 33 , 34 ]. As shown in Table 3 , the Pearson correlation analysis was used to analyze the correlation between the energy density, the laser power, and the laser scanning speed via SPSS.…”

Review on chromium coated zirconium alloy accident tolerant fuel cladding

“…Laser melting is also a potential method for coating pretreatment, which aims to strengthen the adhesion property and improve the surface density of coatings. For instance, laser melting method is used by Hu et al [108] on multi-arc ion plated Cr coating Zr alloy samples. The authors found that an interface metallurgical bonding is formed when the laser energy density is high enough to heat the sample surface higher than the Cr-Zr eutectic point.…”

Deposition behavior of electroless Ni‐W‐P coating on Zr‐4 surface

“…Concerning the coating techniques, laser surface modification, vapor deposition (PVD and CVD), thermal spray, electroless plating, hot isostatic pressing, and microarc oxidation are widely investigated for cladding coatings. [9,[11][12][13][14][15] Electroless plating has become an irreplaceable surface coating technology because of its advantages such as being suitable for various substrates, uniform thickness, no electrical energy required, and favorable coating performance. [16] Electroless nickel plating is the most common electroless plating method.…”