Laser cladded Cr–W–C co-based alloy layer with enhanced hardness,wear resistance,and corrosion resistance on 30CrNi2MoV steel

Abstract

To mitigate the vulnerability of 30CrNi2MoV steel to wear-induced failure and corrosion degradation in extreme service scenarios (i.e., high-temperature/high-load sliding conditions and chloride-rich media), a Cr-W-C reinforced Co-based functional cladding layer was deposited onto the steel substrate via laser cladding. This work systematically characterized the cladding layer in terms of macroscopic deposition quality, microstructure evolution, phase composition, microhardness distribution, tribological performance, as well as electrochemical and neutral salt spray corrosion behaviors, and its core focus was to clarify the synergistic correlations between the cladding layer's structure and integrated properties. Results indicate that the cladding layer presents a continuous, dense fish-scale overlapping morphology (average thickness: ∼1.1 mm), forming a wavy metallurgical bonding interface with the substrate. The absence of macroscopic cracks or porosity confirms the superior deposition quality of the cladding layer. A distinct through-thickness microstructural gradient is observed: fine dendritic/cellular structures dominate the top region, transitioning to directionally solidified fine dendrites in the middle layer and planar crystals at the substrate-cladding layer interface. The formation of this gradient can be qualitatively related to the variation in thermal gradient (G) and solidification rate (R) during the cladding process. XRD analysis identifies a γ-Co matrix as the primary phase, embedded with hard carbide phases (Cr₂₃C₆, Cr₂₂WC₆, and CoC_x), thereby forming a composite phase structure in which a tough matrix is reinforced by a hard-phase framework. In the top 1.0∼1.2 mm region of the cladding layer, microhardness values fall in the range of 630∼650 HV_0·2, marking an increase of close to 90% over the ∼330 HV_0·2 hardness of the 30CrNi2MoV substrate. Notably, the microhardness profile exhibits a relatively smooth transition across the interface, which is beneficial for alleviating stress concentration. Tribological tests show that the cladding layer reduces the average friction coefficient from ∼0.52 (substrate) to ∼0.30, while the wear mass loss decreases from ∼6.9 mg to ∼2.6 mg (a ∼60% reduction); accordingly, the degradation process transitions from intense abrasive-adhesive wear at the base to gentle plowing and surface wear at the cladding layer level. The electrochemical profiling in a 3.5 wt.% NaCl solution reveals that the cladding layer's corrosion current density decreases to 10⁻⁷ A·cm⁻², a full order of magnitude lower than that of the base material. Moreover, the electrochemical impedance spectroscopy (EIS) data indicates a marked rise in charge-transfer resistance. Furthermore, neutral salt spray tests confirmed the cladding layer's robust protective capabilities. After 200 h exposure, the surface was largely unscathed, with only a thin, uniform corrosion-resistant layer present. These outcomes offer reliable theoretical support and practical references for the surface strengthening and performance optimization of such alloy components.