The invention discloses an etchant for displaying a 690
nickel-base
alloy deposited
metal grain boundary and an
etching method thereof. The etchant comprises
ferric chloride, EDTA, deionized water andconcentrated
hydrochloric acid. The surface of the 690
nickel-based
alloy deposited
metal surface is successively wiped with the etchant and a
nitric acid ethanol solution. Thus, it is possible to intuitively observe that the surface of a sample changes from bright to frosty during an
etching process, and the
weld bead can be clearly observed by naked eyes in order to better control the degree ofcorrosion, completely and clearly show the grain boundaries of the deposited
metal sample grains, and avoid the covering by
corrosion products. The etched different grains have different shades due to different orientations. The columnar
crystal structure can be clearly observed and the grain boundaries are clear and complete. The etchant is made of simple raw materials, nontoxic, environmentallyfriendly, convenient in
liquid waste disposal, low in cost, and stable and easy to control in a reaction process. The
etching method is simple and easy to use, and provides detection basis for the
process quality control, the process plan and the quality analysis of nuclear
welding deposited layer, and has very important practical significance.