Investigation on Interfacial Adhesion Enhancement Mechanisms of TiAlN Coatings on Nitrocarburized 300M Steel

This study investigates the interfacial adhesion enhancement mechanisms of TiAlN coatings deposited on nitrocarburized 300M ultra-high-strength steel substrates. Through radio frequency （RF） magnetron sputtering technology， TiAlN coatings （approximately 4 μm thick） are fabricated on both pristine and plasma-nitrocarburized （PNC） substrates. Comparative analyses of phase composition， microstructure， and mechanical properties are conducted using field emission scanning electron microscope （FESEM）， X-ray diffraction（XRD）， nanoindentation， and scratch testing. Molecular dynamics （MD） simulations with Materials Studio （MS） software elucidate atomic-scale interactions between TiAlN coatings and substrates. Results demonstrate that the PNC pretreatment generates a dual-phase structure （about 65 μm thick） comprising the γ-Fe4N compound layer and a high-hardness diffusion layer， establishing a continuous hardness gradient at the coating-substrate interface. The PNC/TiAlN composite coating exhibits enhanced interfacial adhesion strength， attributed to mechanical interlocking from plasma-etched microvoids and optimized lattice matching. Scratch tests reveal a significant increase in critical load to 60 N for coating delamination in PNC/TiAlN systems compared with monolayer coatings. These improvements mitigate brittle spallation risks while maintaining superior hardness （29.26 GPa） and wear resistance. This paper provides atomic-level insights into adhesion enhancement mechanisms and proposes a viable duplex surface engineering strategy for high-strength steel components.