Research On Surface Strengthening Effect Of Fe-Ni Alloy By Laser Shock Processing

Laser shock processing (shortened form is LSP) is a new surface modification technology. In the process of LSP, the laser with high power density and burst pulse irradiates on metal materials, the coating on the material surface vaporized rapidly, forming plasma, the plasma exploded to induced high pressure shock wave, which can modify the microscopic structure of material superficial cost. So that LSP can increase some mechanical properties of metal materials, such as surface hardness, wear strength, corrosion resistance, fatigue resistance and so on. LSP can effectively strengthen materials without changing chemical components of material surface, especially can prolong the fatigue life of metal materials greatly. LSP has extensive applied foreground in some modern manufacturing such as aerospace industry, motor-dom, internal combustion engine manufactory and so on.Fe-Ni alloy is typical alloy for martensite transformation research. As a new processing technology, laser shock processing (LSP) is also a new method of martensite transformation. So laser shocking Fe-Ni alloy is meaning for martensite transformation research.In this paper, the change of crystal grains and organization of different pretreated samples were observed with JXA-840A scan electron microscope, and the austenite content of samples treated based on different crafts was measured with X-350A residual austenite analysis instrument. The effect of Fe-Ni alloy pretreatment on LSP is studied, and the properties change of laser shocked samples was studied, too. Prepared laser shocking samples, and laser shocked these samples and the copious cooling samples with shock energy 70J, the power density 17.84GW/cm~2, then compared the results.The results indicates that Fe-Ni alloy diffusion annealed for 72 hours at 1200℃, cooling in the air; and austenized for 6 hours at 1150℃, quenched in the 10% brine (wt%=10%), then uniform austenite were obtained. The results of laser shock processing indicated that profile of shock zone was clear, the surface of shock zone was smooth, the roughness of material didn't increase. The test results showed that the shock zone maximal depth of the samples quenched in the 10% brine were 16 μm, the shock zone maximal depth of the samples quenched in liquid nitrogen were 12 μ m.