Grain refinement and polymorphic precipitation of Ni–NbC coatings via ultrasonic vibration assisted laser cladding

Abstract

Ultrasonic vibration assisted laser cladding (UVALC) is an effective approach for enhancing the performance of wear-resistant coatings through microstructural regulation. In this study, Ni-based coatings reinforced with 20 % NbC particles were fabricated on H13 steel substrates via UVALC under different ultrasonic power levels. The results revealed that ultrasonic vibration significantly refines the grain size, decreasing it from 21.58 μm to 10.84 μm, and promotes the polymorphic precipitation of hard phases, such as CrB and Cr7C3. The cavitation and acoustic streaming effects improve the dispersion of reinforcement particles and break the preferential grain orientation, leading to the formation of a fine-grained, isotropic, and dense microstructure. Compared with the coatings without ultrasonic assistance, the ultrasonic vibration-treated NbC-reinforced nickel-based coatings exhibit a microhardness increased of 8.3 %–813.25 HV0.3, a compressive strength increased by 12.2 %–1503.48 MPa, an impact toughness increased by 8.7 %–40.48 J, and a corrosion current density reduced by 62.6 % to 1.699 × 10−6 A·cm−2. Moreover, under high-temperature conditions of 600 °C, the optimized coatings show a reduction in the average wear rate from 3.55 × 10−5 mm3/(N·m) to 2.61 × 10−5 mm3/(N·m), which is attributed to the formation of a dense oxide glaze layer and the improved load distribution. This work establishes the process-structure-property relationship for NbC-reinforced coatings and provides a technical pathway for the development of high-performance coatings in extreme service environments.

Keywords

• Ultrasonic vibration assisted laser cladding
• Polymorphic precipitation
• High-temperature wear resistance
• Grain refinement
• Ni–NbC composite coatings