Study of the Gamma Radiation Induced Change on the Surface Morphology of Electroless Ni–P Deposited AISI 304 Stainless Steel

In this research electroless Ni–P coatings were deposited on AISI 304 stainless steel. Deposits have been irradiated in 30 % H₂O₂ environment with a ⁶⁰Co gamma source at a dose rate of 0.48 Gy/s at ambient temperature. The effect of gamma radiation on surface characteristics of electroless Ni–P coated AISI 304 stainless steel was investigated. Scanning electron microscopy results revealed that the Ni–P deposit was completely cracked and fragmented after gamma radiation. Energy-dispersive X-ray examination showed high oxygen and phosphorous content on the surface after gamma radiation. According to X-ray diffraction result it originated from the formation of P₂O₃ oxide on the surface after gamma radiation. It was found that gamma radiation of Ni–P deposit at H₂O₂ environment caused oxidizing of Ni–P deposit and preferential formation of P₂O₃ oxide. Atomic force microscopy images showed typical nodular structure for Ni–P deposit and clustered structure with positions breaking off between the clusters for Ni–P deposit after gamma radiation.     

Correlation Between Potentiodynamic Polarization Behaviors of Transient Liquid Phase Bonded 2205 Duplex Stainless Steel and the Bonding Constituents

In order to precisely evaluate the contribution of each bonding constituent to the pitting corrosion resistance of transient liquid phase (TLP) bonded 2205 duplex stainless steel (DSS), we have undertaken potentiodynamic polarization (PDP) and microstructural analytic measurements all across the TLP bonded area. The PDP results show that the pitting corrosion resistance of TLP bonded specimens is significantly affected by the presence of certain bonding constituents across the TLP bonded area. Electron microscopy analysis indicates that the formation of complex (Fe,Ni,Cr,Mo)₃P phosphide in the bonding zone (BZ) before the completion of isothermal solidification (IS) as well as the formation of P-rich sigma phase in the diffusion-affected zone (DAZ) following the completion of the IS provides the most preferential sites for the occurrence of pitting corrosion. The PDP results also confirm that the pitting potentials (E_pit) of the TLP bonded specimen before and after IS completion are, respectively, closer to the E_pit of the BZ and the E_pit of the DAZ rather than to those of other TLP BZs.