Research On Hot Corrosion Resistance Of Inconel X-750 Nickel-Based Alloy Treated By Laser Peening

Laser peening(LP),as a new type of surface strengthening technique,can improve the residual stress and hardness of the material surface,as well as inducing dislocation propagation and grain refinement of the surface.In this paper,Inconel X-750 nickel-based alloy was treated by LP and the performance of samples after LP were analyzed and characterized.Based on theoretical analysis and experimental study,the effect of LP on improving high-temperature stability and hot-corrosion resistance were studied.The principal works in this paper are as following:(1)The principle and characteristics of LP technology are introduced.The grain refinement and residual stress mechanism of laser peening surface modification are discussed.The effects of LP on the surface morphology,hardness,residual stress and microstructure of the material were analyzed.Based on the basic theory of thermal corrosion,the mechanism of thermal corrosion resistance of nickel-based alloy strengthened by LP was studied.(2)A set of LP experiments under different pulse energies and different times were conducted on Inconel X-750 nickel-based alloysamples.The surface morphology,roughness,microhardness,residual stress and microstructure of the material under different LP parameters were tested by micro-hardness tester and X-ray stress instrument.It was realized that,within the optimum laser pulse energy range,the micro hardness,residual stress and grain refinement of the material surface increased with the increase of laser pulse energy.The micro hardness,residual stress and grain refinement of the material surface increased after the double LP on the basis of single layer of LP,and the surface roughness of the material decreases.(3)The hot-corrosion test at 950℃ under mixed salt film(75% Na2SO4 + 25%NaCl)was carried out on LP samples and untreated samples and the corrosion kinetics curves of samples were measured.It was found that the corrosion weight loss and corrosion depth of LP samples were significantly lower than those of untreated samples,which was as a result of the dense and stable Cr2O3 oxide film appearing on the corrosion surface.At the same time,SEM and EDS analysis of the surfacemorphology and cross-section of corrosion were carried out.It was found that the grain refinement and residual stress of the material after LP could effectively prevent the intrusion of O2 and S,and so on,which effectively improved the thermal corrosion resistance of the material.