Component Regulation and Cavitation Erosion Resistance of PAI/PU Blend Coatings

ZHANG Zixuan; HOU Guoliang; WAN Hongqi; MA Junkai; ZHOU Huidi; CHEN Jianmin

doi:10.16490/j.cnki.issn.1001-3660.2026.17.007

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Surface Technology ›› 2026, Vol. 55 ›› Issue (17) : 77-88. DOI: 10.16490/j.cnki.issn.1001-3660.2026.17.007

Friction, Wear and Lubrication

Component Regulation and Cavitation Erosion Resistance of PAI/PU Blend Coatings

ZHANG Zixuan^1,2, HOU Guoliang^1,2,*, WAN Hongqi^1,2,*, MA Junkai¹, ZHOU Huidi^1,2, CHEN Jianmin^1,2

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Abstract

In the development of hydropower and marine engineering equipment, flow-passing components often face severe failure risks due to cavitation erosion (CE), which has become a core bottleneck limiting the service life of equipment. This damage occurs through the implosion of vapor bubbles near surfaces, generating intense localized stress cycles. Polyamide-imide (PAI) coatings are characterized by high strength but significant brittleness, making it difficult to dissipate cavitation impact energy through deformation. Although polyurethane (PU) coatings exhibit good flexibility and strong energy dissipation capability, their low modulus and insufficient cohesive strength render them prone to delamination under impact. However, a systematic understanding of how the PU blending ratio affects the macro- and microstructural evolution of PAI coatings and regulates their CE resistance mechanism is still lacking.
To synergistically leverage the advantages of both materials, this study employed a solution blending process to design and prepare a series of PAI/PU composite coatings with varying PU mass fractions (20% to 80%). The coatings were labeled PAIx, where x denoted the mass fraction of PAI resin (e.g., PAI0.4 contains 40% PAI and 60% PU). A comprehensive suite of characterization techniques was utilized, including Fourier Transform Infrared Spectroscopy (FTIR) to analyze chemical structure and intermolecular interactions, tensile testing and nanoindentation to evaluate mechanical properties at different scales, and 3D optical profilometry for surface topography analysis. The CE resistance was rigorously assessed with an ultrasonic vibration accelerated CE test apparatus. The systematic investigation aimed to elucidate the influence of PU content on the chemical structure, mechanical properties, and CE performance of the coatings, establishing clear structure-property- performance relationships.
The results demonstrated that the introduction of PU weakened the intermolecular hydrogen bonding within PAI, thereby enhancing molecular chain mobility. The mechanical properties exhibited a distinct "strength-elasticity" balance, which was non-monotonic.Both excessive rigidity and excessive softness proved detrimental. The PAI0.4 coating (with 60% PU content) achieved the optimal balance, possessing a tensile strength of 42 MPa, an elongation at break of 9%, and a rebound rate of 31%, indicating a combination of load-bearing capacity and energy dissipation potential. In CE tests, the PAI0.4 coating showed the best performance, with a cumulative mass loss of only 1.7 mg after 90 minutes, which is merely 41.5% of the mass loss (4.1 mg) of the PAI0.8 coating. The PAI0.2 coating (80% PU) performed worst, suffering from rapid material loss due to its weak mechanical integrity.
The core mechanism for the excellent CE resistance of PAI0.4 lies in the formation of a "PAI rigid network-PU flexible matrix" bicontinuous structure. Within this structure, the PAI phase provides a load-bearing skeleton to resist cavitation load, while the PU phase dissipates impact energy through chain segment movement. This synergy allows for efficient stress distribution and energy absorption. Furthermore, the PU soft segments undergo preferential degradation during CE, creating a "sacrificial-protection" effect that helps prevent excessive damage to the PAI rigid skeleton. This sacrificial layer absorbs the initial impact, preserving the structural core of the coating. This study provides theoretical support and technical references for the design and application of high-efficiency CE-resistant coatings for flow-passing components.

Key words

cavitation erosion / polyamide-imide / polyurethane / blend coatings / energy dissipation / fatigue mechanism

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ZHANG Zixuan, HOU Guoliang, WAN Hongqi, MA Junkai, ZHOU Huidi, CHEN Jianmin. Component Regulation and Cavitation Erosion Resistance of PAI/PU Blend Coatings[J]. Surface Technology. 2026, 55(17): 77-88

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Funding

Supported by the Strategic Priority Research Program of the Chinese Academy of Sciences (XDB0470102), the Natural Science Foundation of Gansu Province (Grant No. 24JRRA161), the Longyuan Youth Talent Project, and the Youth Innovation Promotion Association of the Chinese Academy of Sciences (2020416)