Effect of Ultrasonic Rolling on the Surface Integrity and High Temperature Oxidation Properties of Laser Melted NiCrAl Coatings

This study investigates the effects of ultrasonic surface rolling process (USRP) parameters—static load, indentation depth—on the surface integrity, mechanical properties, and high-temperature oxidation properties of laser-clad NiCrAl coatings. Comprehensive experimental results demonstrate that USRP treatment effectively eliminates surface cracks and significantly enhances surface integrity. The process simultaneously improves mechanical properties, with microhardness increasing by 24.6% due to grain refinement-induced strengthening and elevated dislocation density. Under constant preload, increasing the ultrasonic rolling indentation depth effectively transforms residual tensile stress into beneficial compressive stress (from +69.8 MPa to −1315.3 MPa), with higher preload further enhancing this effect. Moreover, USRP-treated coatings achieve complete oxidation resistance at elevated temperatures by forming a denser and more continuous oxide layer while effectively suppressing internal oxidation, resulting in markedly improved high-temperature oxidation performance. Quantitative analysis confirms that the enhancement in surface mechanical properties is primarily attributed to microstructural refinement and dislocation strengthening mechanisms.