梯度结构对Ti6Al4V表面Nb2O5/Nb2O5-Ti/Ti多层涂层残余热应力的影响

Effects of Gradient Structure on Thermal Residual Stress of Nb2O5/Nb2O5-Ti/Ti Multilayer Coatings on Ti6Al4V

采用有限元法对Ti6Al4V表面Nb2O5/Nb2O5-Ti/Ti多层涂层的残余热应力进行分析,研究中间梯度层Nb2O5-Ti的层数与厚度、成分分布指数对涂层残余热应力的影响,并对其进行优化。结果表明:随着梯度层数由1层增加到6层,深层的残余热应力最大值由12.6 MPa减小到11.7 MPa;但梯度层数继续增大到8层时,残余热应力最大值无明显变化。梯度层越厚,残余热应力最大值越小。当成分分布指数由0.5增大到3.0时,残余热应力最大值呈现先减小后增大的变化趋势,其中分布指数为1.5时的残余热应力最大值(8.93 MPa)最小。通过正交试验法得到了多层涂层的梯度层的最优结构参数组合,即梯度层数为7,梯度层厚度为1μm,成分分布指数为1.5。优化后的多层涂层残余热应力的最大值为8.53 MPa,较Nb2O5单层涂层(20.9 MPa)和Nb2O5/Ti双层涂层(22.1 MPa)的残余热应力最大值分别减小了59.2%和61.4%。

An analysis has been made of the residual thermal stress of Nb2O5/Nb2O5-Ti/Ti multilayer coating on Ti6Al4V by adopting the finite element method,followed by a research and optimization of the influence of the number and thickness of the film layer and composition exponent of the Nb2O5-Ti gradient interlayers on the residual thermal stress.The results show that the maximum residual thermal stress decreases from 12.6 MPa to 11.7 MPa with the increase of gradient interlayers from 1 layer to 6 layers,but the maximum value of residual thermal stress undergoes no significant change with the number of gradient layers increasing to 8 layers.The thicker the gradient layer is,the smaller the maximum residual thermal stress will be.When the composition exponent increases from 0.5 to 3.0,the maximum residual thermal stress first decreases and then increases,and the maximum residual thermal stress(8.93 MPa)is the minimum with the composition exponent being 1.5.The optimal combination of structural parameters of the gradient layer of multilayer coating can be obtained by using the orthogonal test method,i.e.,with the number of gradient layers being 7,the thickness of each gradient layer 1μm,and the composition exponent 1.5.The maximum residual thermal stress of the optimized multilayer coating is 8.53 MPa,which is 59.2%and 61.4%lower than that of Nb2O5 monolayer(20.9 MPa)and Nb2O5/Ti bilayer coating(22.1 MPa),respectively.