High-Temperature Fretting Fatigue Mechanisms and Microstructure-Sensitive Life Modeling of Laser-Clad IN718/WC Composite Coatings

Very-high-cycle fretting fatigue (VHCFF) behavior at elevated temperatures is critical for the safety and longevity of aerospace components. This study investigates the VHCFF mechanisms of laser-clad IN718/20%WC composite coatings at 650 °C. Fatigue tests were conducted to generate S-N data, and the resulting wear and fracture morphologies were characterized. Crack initiation was found to preferentially occur in grains exhibiting higher Schmid factors, lower elastic moduli, and larger equivalent sizes. To simulate fretting fatigue, a crystal plasticity finite element model (CPFEM) incorporating the actual microstructure was developed. An improved fatigue indicator parameter (FIP) was proposed, which integrates multiple physically significant factors including plastic strain, dislocation density, elastic modulus, and grain size. Life predictions based on a critical FIP value demonstrated high accuracy, with 97.6% of the results falling within a ±3.5 scatter band of the experimental data, confirming the model’s effectiveness in predicting crack initiation life.