激光重熔对等离子喷涂ZrO_2-NiCoCrAlY梯度涂层组织与性能的影响

LASER REMELTING TREATMENT OF PLASMA SPRAYED ZrO_2－NiCoCrAlY GRADED COATING

在保证梯度涂层的成分分布方式不被影响的前提下，对其ZrO2表面层进行了激光重熔处理．经重熔处理后，ZrO2熔化区形成了致密的结晶组织，其硬度得以大幅度提高，涂层的抗氧化性能得到较大的改善．同时，由于涂层经受了严重的不均匀受热－冷却过程，在涂层中形成了较大的残余热应力，使ZrO2晶粒发生强烈畸变，并致使熔化区表面形成网状裂纹和少量纵向裂纹贯穿熔化区，降低了熔化区与未熔涂层间的结合强度，对涂层的抗热震性能造成不良影响．

The laser remelting treatment of plasma sprayed ZrO2－NiCoCrAlY graded coating on TC4(Ti－6Al4V) alloy substrate was investigated. In order to maintain the gradual compcaitinn distribution， the laser remelted zone was controlled in ZrO2 top layer. Laser remelting treatment diminished the pores in the ZrO2 top layer and resulted in a dense microstructure. Compared with the unmelted coating， the ZrO2 melted zone had a higher micrcahardness and a more excellent oxidation resistance. However， owing to the graded coating being heated and cooled unevenly by the laser beam， a serious residual thermal stress was produced in the coating. Laser remelting distorted the ZrO2 grains， some coarse cracks were formed in the coating， and the adherence strength between ZrO2 top layer and graded layers was weakened. As a result， the thermal shock property of the graded coating was worsen.