Low-Temperature Mechanical Properties of Laser-Cladded Alloy Coatings on EH40

Four alloy coatings were deposited via laser cladding on EH40 steel: a Co-based coating (HG), a Ni-based coating (P0), and two Ni-based composite coatings containing 15 wt.% WC (P15) and 30 wt.% WC (P30). Their low-temperature mechanical properties—hardness, tensile strength, shear strength, and impact toughness—were systematically investigated. Hardness increased with WC content, with P30 being the hardest. HG exhibited the highest tensile strength (577 MPa), exceeding the EH40 substrate baseline. Shear tests revealed strong anisotropy: P0 was stronger longitudinally, but WC addition reversed this trend. P30 showed critically low longitudinal shear strength (187.1 MPa), while HG demonstrated high, nearly isotropic shear performance. Impact toughness decreased for all coatings at lower temperatures (−40 °C to −80 °C). P30 maintained good impact energy at −40 °C and −60 °C but suffered severe embrittlement at −80 °C, correlating with its poor longitudinal shear strength. HG offered the best balance of high strength and isotropic properties. P15 provided a reasonable compromise between enhanced hardness and retained toughness. This study highlights the critical trade-off between surface strength and bulk impact toughness for laser claddings on high-strength steel in low-temperature service.