灰铸铁表面激光重熔的数值模拟与工艺试验

Numerical Simulation and Experiments of Gray Cast Iron by Laser Surface Remelting

通过建立三维瞬态仿真模型,分析了HT250灰铸铁在激光重熔过程中的温度分布及其变化规律,探讨了激光功率对激光熔池温度场的影响。利用超景深显微镜和扫描电镜,观察了激光单熔道的几何特征和显微组织,用硬度计测试了熔道横截面的显微硬度。研究结果表明,激光重熔后,熔道呈半圆弧形,由表层向内依次为重熔区、热影响区和母材,激光功率增加,激光熔池的峰值温度升高,熔道的深度加深、宽度加宽。数值模拟激光熔池的计算几何尺寸,与工艺试验中激光重熔熔道的实际测量值基本相吻合,证明了模型的可靠有效。另外,工艺试验结果表明,HT250灰铸铁重熔区的显微组织为细小的树枝状变态莱氏体,重熔区的平均硬度约为1000 HV,约为母材硬度的5倍。

The temperature distribution and variation of HT250 gray cast iron during laser remelted are analyzed by establishing a three-dimensional transient simulation model,and the influence of laser power on the temperature field of laser melting pool is discussed.The geometric characteristics and microstructure of laser remelting single channels are observed by metallographic microscope and scanning electron microscope,respectively.The microhardness of the channel’s cross section is measured by the microhardness tester.The results show that the remelted zone is semiarc.From the surface to the inside,the remelted zone,the heat affected zone and the base metal are in turn.With the increase of laser power,the peak temperature of laser molten pool increases,the depth increases,and width of melt track deepens.The calculated geometry of the laser melted pool is in good agreement with the actual measurement of the laser melted pool,which proves that the model is reliable and effective.In addition,the experimental results show that the main microstructure of the HT250 gray cast iron in the remelted zone is very small dendritic modified ledeburite.The average microhardness of the remelted zone is about 1000 HV,which is about 5 times higher than that of the substrate.