Ni/ZrO2梯度镀层高温氧化性能及热应变特性

采用复合电沉积法制备Ni/ZrO2梯度镀层.SEM测试表明,沿镀层生长方向,ZrO2含量由0逐渐增加到21%(体积分数),呈梯度分布;高温氧化实验结果表明,梯度镀层在800℃处理24h后氧化增重仅为纯镍镀层的1/6,氧化处理并未改变镀层中ZrO2微粒的梯度分布.结构分析表明,ZrO2微粒的掺杂使梯度镀层晶粒细化,结晶细致,可阻止高温氧化时氧原子向金属内部扩散.弥散分布的ZrO2对金属镍高温氧化时具有活性元素效应,可阻止Ni的短路扩散,降低氧化增重速率.因此,Ni/ZrO2梯度镀层具有优良的高温氧化性能,可用于高温氧化气氛之中.热应变特性研究表明,沿镀层厚度方向,热应变变化平缓,有效地缓解了界面处材料热失配,从而降低了材料的热应力.

Studies on oxidation resistance and thermal strain of graded nickel/zirconia deposits

In this work the Ni/ZrO_2 gradient deposit is prepared by the method of composite electrochemical deposition.SEM investigation indicates that the content of the ZrO_2 powder increases gradually from 0 to 21vol% in the direction of deposition.Oxidation test shows that the mass gain of the graded Ni/ZrO_2 deposit is only 1/6 of that of Ni deposit after 24h oxidation in air at 1073K.X-ray diffraction(XRD) analysis indicates that the grain size of the gradient deposit is smaller than that of Ni deposit after oxidation at the same temperature.Decreased grain size of the gradient deposit leads to a more compact deposit,which hinders the diffuse of oxygen atoms to the inner of the deposit.In addition,ZrO_2 articles segregated at the NiO grain boundaries retard the short distance diffusion of Ni~(2+),hence increase the performance of oxidation resistance.Furthermore,the strain distribution in the Ni/ZrO_2 gradient deposit determined by the digital-image correlation method can eliminate the mismatch of thermal expansion coefficients at the interface,thus the thermal stresses in the coating are easy to be relaxed.