针对激光熔覆过程中温度变化对其凝固组织的影响,讨论了温度梯度G与冷却速度（即降温阶段的温度变化率）对凝固组织的影响,利用形状控制因子K分析了激光熔覆过程的凝固行为。分析结果表明：在热源中心的正下方晶粒是沿基体垂直方向析出的;冷却速度有细化晶粒的作用,冷却速度越大,晶粒越细小;熔覆材料或基材达到熔点的时间与达到最大冷却速度时间的先后顺序对其凝固组织形态有重要影响,若冷却速度先达到最大值,其组织呈胞状晶粒,否则,其组织呈柱形树枝晶。K在80×106～120×106℃.s时,凝固组织为密布排列且粒径较大的胞状晶粒;当K大于200×106℃.s时,凝固组织为柱形树枝晶。%Finite element was used to analyze effects of the temperature variations on the solidification organization for laser cladding.The influences of the temperature gradient G and the cooling rate（cooling part of temperature changing rate） were discussed.A feature controlling factor K was used to study the solidification performance in the laser cladding process.The results show that the grains precipitate along the vertical direction below the heat source center and the cooling rate plays an important role in refining the grains.The larger the cooling rate is,the less the grains are.It is also found that the solidification structure is significantly dependent on the occurring time of the highest cooling rate and on that of K at the melting point of the cladding or the substrate.It is demonstrated that,if the largest cooling rate is achieved prior to K at the melting point,the structure is of the cellular-grain form.Otherwise,it is of column-dendrite grain form.And when K is in the range of 80×106~120×106℃·s,the solidification structure is of densely arranged cellular-grain form whose grain size is larger.When K is more than 200×106℃·s,the structure is of column-dendrite form.
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