Abstract
The low-carbon martensitic stainless steel CA6NM is widely used in the impellers of hydroelectric and nuclear power units due to its advantages of high hardness, corrosion fatigue strength, and good fracture toughness. In order to analyze the number of repair welding times on the properties of heat-affected zone (HAZ, the most unstable area of welded joint property) in CA6NM, the microstructure and mechanical properties of HAZ with once-repaired welds (1R) and twice-repaired welds (2R) were tested. Through data analysis, the following conclusions are drawn for welded joints: (1) the grain size of HAZ with a different number of repair welding processes is smaller than that of the base material; (2) the density of texture concentration is reduced and the directionality is not obvious; (3) the density of twins and dislocations are increased; (4) the hardness and impact energy of HAZ of the 1R and 2R specimens are higher than that of the base material.
Highlights
It can be established from the XRD pattern of the base material region that the base material is basically composed of a Ni-Cr-Fe phase with body-centered cubic (BCC) structure
The phase composition in the heat-affected zone obviously changes compared with the base material
The martensite beam basically disappears, and the heat-affected zone is replaced by equiaxed grains
Summary
With the development of society and the progress of science and technology, the demand for electricity is consistently increasing. With the increase of environmental pollution and the greenhouse effect, the frequency of extreme weather is on the rise. These phenomena have brought significant risks to people’s lives and property. Many countries are investigating new clean energy resources to reduce pollution and improve the living environment. Nuclear power generation is a clean energy resource, the safe operation of nuclear power plants and nuclear radiation protection remain issues of general concern. These have promoted the continuous development of nuclear power generation technology and the improvement of the construction and operation of nuclear power plants
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