High Pressure Solidification Behavior Of SLM Micro Melting Pool

Selective laser melting technology is one of the most promising additive manufacturing technologies and is developing rapidly.High nitrogen stainless steel is a kind of steel with excellent properties and is widely used in daily life.A new high pressure selective laser melting(HP-SLM)process was developed for the preparation of high nitrogen stainless steel by applying selective laser melting technology to the process of high nitrogen stainless steel.The temperature field during the solidification process of 20 ?m,30 ?m,40 ?m and20 mm molten pool was simulated by numerical simulation method,and the variation of temperature field during the solidification process of micro and macro molten pool was analyzed.The evolution of solidification microstructure in a 20 ?m molten pool was investigated and analyzed by numerical simulation experiments.The effect of high pressure on the surface solidification quality of SLM printing parts was observed by using stainless steel and high nitrogen stainless steel powder.The results show that the cooling rates of the 20 ?m,30 ?m and 40 ?m molten pool are 24135 ?/s,14685.9 ?/s and 12142.4 ?/s,respectively.In the simulation experiment,the temperature field and the change curve of solid rate coincide,which indicates that the solidification process of the micro-molten pool has the characteristics of instantaneous solidification and rapid cooling.The XZ section of the micro-molten pool is mostly columnar grain,about 57.9%.The change of Cr,Mn,N and other alloying elements has no effect on the solidification microstructure of micro pool,but has an effect on the solidification microstructure of large pool.In the high pressure hot state experiment,the chamber pressure increases,which inhibits the spheroidization during SLM printing.Under the laser power of 200 W,the surface forming ratio of the high nitrogen stainless steel samples increases from 81.9% to 98.2% with the increase of the pressure,and the surface solidification quality of the samples is significantly improved.Figure 61;Table 27;Reference 77...