Abstract: Inconel 625 alloy cladding layer was prepared on AISI 4130 steel surface by hot-wire tungsten inert gas (TIG) welding under a low current (peak/base currents of 160 A/95 A) and different welding speeds (220–300 mm · min⁻¹). The effects of welding current and welding speed on the formability and microstructure of the cladding layer were investigated, and compared with those at a high current (peak/base currents of 190 A/110 A). The results show that at the low current, with the increase of welding speed, the width, depth of fusion of the cladding layer decreased, and the height and the ratio of depth of fusion to height of the cladding layer first decreased and then increased. The width, depth of fusion and the ratio of depth of fusion to height of the cladding layer at the low current were lower than those at the high current, and the height was higher than that at a high current. Low current and low welding speed could obtain the narrow and high cladding layer with low dilution rate. At the low current, cellular crystals and dendritic crystals were mainly formed near the surface and away from the bottom of the molten pool on the cross-section of the cladding layer, and planar crystals were dominant at the bottom of the molten pool. With the decrease of welding speed, the planar crystal region expanded, the grains near the surface developed into columnar or dendritic crystals, and the grains away from the bottom of the molten pool developed into cellular crystals. Under 160 A/95 A peak/base current, 240 mm · min⁻¹ welding speed and 30% bonding rate, the three-layer ten-pass cladding layer was continuously dense and the microhardness was (280±20) HV. After cladding welding, annealing treatment was required to reduce the hardness.