Study On The Key Technology Of Ti Alloy In Selective Laser Melting

Selective laser melting is an important branch of rapid increasing material manufacturing technology. Balling phenomena crack and porosity has been a bottleneck restricting the development of the progress. With its excellent mechanical properties and good corrosion resistance, light quality, heat resistance, good biocompatibility and other characteristics, Titanium alloy would be widely applied in the aerospace, biology and other prospects. In this paper,Ti6Al4 V powder was regarded as research object. Studied the key technology during the process of SLM. The main subjection is on the cause of formation,influence factors, weakening or prevention measures on these questions and the forming capability of SLM Titanium alloy, which has much more practical significance.Balling phenomenon and pore were studied respectively,on rapid prototyping of HRPM- II A,hat made by Hua zhong University of Science and Technology and Wuhan Binhu Electromechanical Industry.The forming reason of large size ball is the wettability of molten liquid metal and solid surface is poor,the molten metal contract into a ball in the surface tension of liquid metal;the small size ball is formed by the liquid splash during processing or high-energy laser beam impact the molten pool; oxygen content increases the amount of balling phenomena, and white oxide floating on the surface of the weld pool also will increase;forming performance of rules and low oxygen containing spherical metal powder is better than water atomized particles in the irregular shape metal powder;The more oxygen content in the processing environment is,the more obvious of balling phenomenon; When absorption in weld pool and energy scanning speeds is low,balling phenomena gradually weakened with the laser power increases; balling phenomena becomes more and more obvious when the weld pool absorb more energy;The faster the scanning speed is,the shorter time of the laser acting on the metal powder,the more obvious the phenomenon of the balling is;but the scanning speed can cause the weld pool to burn, and the scanning speed of the process should be at least more than 15mm/s; the surface quality of molding increases gradually with the scanning spacing increases,but when exceeds a certain limit the forming surface quality decreased with the scanning distance increasing.The suitable distance is0.08~0.12mm;Of all the scanning mode,the jump change mode can reduce or prevent the occurrence of partial balling phenomena,forming surface is good;Balling phenomena increases gradually with the increasing of thickness of the powder layer,the great thickness is 0.06 ~ 0.1mm; large size metal ball,resulting in uneven paving powder,molding face height above the level of theory,cumulative powder spreading error can lead to forming index is not controllable, forming surface quality is getting worse,forming parts incline deformation,rupture or damage the powder spreading roller; at the same Time,balling phenomena will increase the forming parts of the surface roughness,there will be a large number of pores,the gap between adjacent metal balls may entrain part not melting powder,resulting in the prepared sample density is reduced,it is difficult to guarantee the precision of parts.