Study of the microstructure and impact properties of the heat-affected zone of high nitrogen steel for laser-arc hybrid welding

Abstract

The effect of different heat inputs on the microstructure and impact properties in the heat affected zone (HAZ) for laser-arc hybrid welding of high nitrogen steel are studied in this paper. The microstructure and impact properties were investigated using optical microscopy, scanning electron microscopy, and other methodologies. The results showed that the HAZ consists of massive amounts of austenite with small amounts of δ-ferrites. The combination of laser and arc causes the high nitrogen steel to absorb more energy, and the area of the heat affected zone increases as the heat input increases. At an identical heat input, the upper grain size of the HAZ is larger than the lower grain size, and the grain size of the HAZ increases as the laser power and welding current increase, and decreases as the welding speed increases. The impact energy decreases as the laser power and welding electric current increase, and the impact performance decreases as the welding speed increases. The experimental impact specimens showed obvious ductile fracture characteristics, with many dimples distributed on it.