Fabrication Of Cu-based Porous Mirrors By Direct Laser Sintering

Although the application of porous mirrors could solve the probelm of thermaldeformation in high power laser, there is none suitable methods to fabricate the porousCu-based mirrors. It’s difficult to connect the mirrors and the commercial foam metal withtraditional technology, such as braze which would filled the pores because of the capillaryforce. A high porosity Cu-based mirror was fabricated successfully using direct lasersintering in this thesis. The effects of porogen to laser sintering and porous structure werestudied. Some value conclusions have been obtained, which are listed as follows:(1) Firstly, the surface modification treatment of Cu substrate has been investigated.The processes such as shot blast, oxidation, laser cladding were utilized. Further analysis ofmetalloscope, SEM(Scanning Electron Microscope), EDX(Energy Dispersive X-RaySpectroscopy) shows that the metallurgical bonding between the Cu substrate and thesintered layer has been achieved.(2) Secondly, direct laser sintering of Cu-based metal powders on the Cu substrate hasbeen carried out, the porous Cu-based mirrors were obtained. The sintering was based onliquid-phase sintering mechanism by using Cu and CuP powders.(3) Lastly, during the laser sintering, NaCl and MgSO4powders were utilized as theporogen in the powder mixture, the influences of these two porogens on the sinteringbehavior and the performances of the porous structure have been investigated. Whenporogen MgSO4was added in the powder mixture, O2is generated since MgSO4decomposes,inducing the oxidation of Cu and balling effect. During the laser sintering, NaCl melts,inducing a larger amount of liquid phase, whose effect is similar as the liquid phase insintering. After NaCl removed, the dense and strong longer-bar shape tracks with largeramount of pores in the microstructure can be obtained. The effect of the NaCl content on themicrostructure morphology and porosity of the sintered sample was also investigated in thispaper. The results reveal that the size of pores as well as the porosity of the sintered sample increase with the NaCl content in the powder mixture. The porosity is57%as the mass ratioof NaCl and metal powders is0.5. Infiltrated experiment verifies the pores in the structureare inter-connected.