Effect of Cr content on microstructure, mechanical properties and corrosion behavior of weld metal in weathering steel of high-speed train bogie

Abstract The effects of Cr content on the microstructure, mechanical properties and corrosion behavior of two weld metals containing Ti or Mo in the Ni-Cu alloy system for high-speed train bogies were studied. The results show that: In the weld containing Ti, Cr increases the acicular ferrite by about 15%, decreases the GF and FS, and slightly increases the M-A constituents. the effect of Cr on toughness is not obvious. In the weld containing Mo, Cr almost did not change the acicular ferrite content, resulted in a decrease in GF and an increase in FS, and a substantial increase in M-A constituents in the as-welded zone (0.4–2.5%). Cr reduces weld toughness due to increase the proportion and size of M-A constituents and coarsen inclusions, the impact energy at -40℃ and − 60℃ decreases by 44J and 16J respectively. For the corrosion resistance, the initial corrosion rate of Mo-containing welds is reduced by addition of Cr, mainly due to the formation of MnS on the inclusions, which absorbs Cr, is suppressed, MnS is easily dissolved. While in Ti-containing weld this effect is weakened. In addition, Cr densifies the inner and outer rust layers and then reduces the corrosion rate of weld rust layers.