The interface microstructure, micro-hardness, and tensile properties of hot isostatic pressing (HIP) densified Inconel 690 cladding on low alloy steel were investigated during the 600℃-aging process. The interface region can be divided into four zones - carbon-depleted zone (CDZ), partial melting zone (PMZ), planar growth zone (PGZ), and brownish feature zone (BFZ) - from base metal to deposited metal. Dimensions of these zones do not significantly change during aging. However, type Ⅰ carbides noticeably increase in size in the PMZ, and precipitates clearly occur in the PGZ. The main reason for their growth and occurrence is continuous carbon migration. Micro-hardness of the interface shows that the highest hardness appears in the PGZ and BFZ region, which is related to carbon accumulation and precipitates in this region. Tensile failure occurs on the base metal side due to the high strength mismatch between these two materials and is located at the boundary of CDZ and base metal due to the lower strength of only ferrite. The ultimate tensile strength decreases by only 50 MPa after aging for 1500 h, and the interface region maintains high strength with no significant deformation.