Ti-6Al-4V基体激光植入ZrO2颗粒工艺过程数值分析

Numerical research on the Ti-6Al-4V strengthen process by laser melt injection of ZrO2 particles

摘要:

为了提高Ti-6Al-4V合金零部件的表面强度及耐热性能，在利用激光熔化后的Ti-6Al-4V材料表面上植入ZrO2陶瓷颗粒。本文基于CFD计算方法建立了三维瞬态激光植入工艺过程数值分析模型并对部分实验结果进行了验证。该模型根据等效热效应对移动激光热源进行计算，利用VOF方法追踪流体的自由表面。考虑浮力、惯性力、粘性阻力对颗粒运动的影响分析了颗粒在熔池内的运动过程，对比分析了是否添加颗粒两种工况下熔池内的温度场与流场分布。结果表明颗粒的进入使得熔池内温度场与流场重新分布，流体的流动和熔池的凝固使颗粒分布于不同位置。通过对100μm深度上熔池不同位置处的颗粒数进行统计发现，随着激光扫描速率的增加，颗粒在基板上表面的分布更加密集。

Abstract:

In order to improve the surface strength and heat-insulating capability of Ti-6Al-4V alloy, ZrO2 particles were injected into the Ti-6Al-4V surface melted by laser. In this paper, the melt-injection-interaction process was modeled using CFD method and the simulations were partly verified by experiments. In this model, the moving gauss laser was defined based on the equivalent thermal effect. VOF method is adopted to analyze phase change process and detect the free surface of molten pool. The buoyancy, inertia force and viscous drag were considered when calculating the particle movements. Temperature and velocity fields inside the molten pool were analyzed, and the influences of the convection caused by thermal-fluid coupling on particles injection and distribution were revealed. The results show that the temperature field and flow field in the molten pool are redistributed with the entry of the particles and the fluid flow and the solidification of the molten pool distribute the particles in different positions. The number of ZrO2 particles was counted per 100 μm depth, it’s found that with the increase of laser scanning velocity, particle densest positions became closer to the substrate surface.