Effect of dilution and macrosegregation on corrosion resistance of laser clad AerMet100 steel coating on 300M steel substrate

To improve the corrosion resistance of low alloy ultra-high strength steel 300M, AerMet100 steel coating was fabricated on 300M steel using laser cladding under different laser powers and scanning speeds. Chemical compositions, hardness, microstructures and corrosion resistances of the coating were investigated. Results show that as-laser clad AerMet100 steel layer consists of fine lath martensite, a small amount of retained austenite and rod-shaped ξ-carbides within the martensitic laths. Dilution ratios of the layers increase with the increase of laser powers and scanning speeds. Macrosegregations took place in AerMet100 steel coatings when convection of molten liquid is insufficient, and which could be avoided by applying high laser power as well as slowing down the scanning speeds. The corrosion resistance of 300M steel substrate could be greatly improved after coating with the AerMet100 steel. High dilution ratios and severe macrosegregations are observed to degrade the corrosion resistance of clad layers by reducing the alloy elements Cr, Mo and Ni in the zones where riches in 300M steel.