Effect on the microstructure of deposit metal nanostructured powders

The experimental results of the effect of nanostructured powder modifier on the microstructure and corrosion resistance of weldments are presented. Specimens were fused by two methods: welding by solid cross-section wire, with the addition of nanosized tungsten powder in a medium of argon (W); and welding by solid cross-section wire, with the addition of nanosized molybdenum powder in a medium of argon (Mo). Welding conditions were the same in both methods. The joint welds were studied by an optical metallography method using the Neophot 21 microscope. Сorrosion tests of the welded specimens were conducted according to State Standard 6032. Weld composition study before and after corrosion tests was performed using the Solver PH47-PRO atomic-force microscope by the contact method. The weld metal has a layered structure, which is caused by changes in the heat dissipation conditions while it moves deeper into the melt pool. It is shown that the addition of nanostructured modifiers leads to decrease in the size of the dendrite and the best equilibrium structure is formed, which increases the corrosion resistance of weldments. It has been observed that through the addition of nanostructured powder of Mo and W into metal weld, intercrystalline corrosion of the welding joint does not occur. It is established that the increase in corrosion resistance increasing with the modified surface of layer results from the different orientation of dendrites and crystallography. The lowest depth of etching was found in a sample modified with tungsten nanopowder; therefore, during corrosion tests, it was least affected by etching. The greatest impact on the environment was on the sample without additives of nanomodifiers. Thus, the weld joint in the specimens modified by molybdenum nanopowder is inferior to the sample modified by tungsten

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