The Formation Mechanism of Reaction-Phases and its Regulation on a Solid-State Bonding Silicon-Nitride Ceramics to Metals

研究结果表明，在低压粘结的情况下，反应层的形成有一定的时间滞后，但对反应层本身的结构没有影响。在abobu 1403 K下，不同氮化硅陶瓷的反应层结构差别不大。用2.0- 3.5 μ m厚的镀铬镶块连接的Si_3N_4/SUS 304偶件，室温下的抗弯断裂强度最高，达440 MPa。在低于1423 K的温度下加热连接初期，Ni侧形成Ni-Cr固溶体，Ni与Cr镀层界面形成Cr_2N，连接界面附近形成Ni-Cr-Si三元合金。然后，Cr_2N转变为CrN，并在结合界面形成CrN、（Cr_3Si）和Ni-（Si）合金的混合相。该混合相的厚度取决于镀铬层的厚度。在反应层的形成使作为镀层的Cr消失后，扩散的Ni通过混合相与Si_3N_4发生另一反应，形成低熔点的Ni-Cr-Si三元共晶合金，使合金相熔化，Si_3N_4受到侵蚀，已形成的CrN相分解。在1473 K下的连接中，在连接界面处形成了致密的CrN相，其中含有少量的Ni-（Si）合金，从而抑制了熔合相的形成。用预先退火的镀铬镍片作为插入物，可以形成类似的紧密凝聚的CrN相。研究结果表明，在钼板上采用镍、铬双层镀层的镶块，有可能获得较高等级的耐热性结合。

The summary of the results of this research is shhown below.In the case bonded under low pressure, there is a slight time lag in the formation of reaction layrs, but there is no influence on the structure itself of reaction layres. There is a little difference in the structure of reaction layrs for different silicon-nitride ceramics bonded at abobu 1403K.The fracture bending strength of Si_3N_4/SUS304 couple bonded with the insert Cr-plated 2.0-3.5mum in thick showed the maxmum of 440MPa at room temperature. At early stage of the heating to bond at less than 1423K,Ni-Cr solid-solution at Ni side, Cr_2N at the interface of Ni and Cr-plating layr and Ni-Cr-Si ternary alloy at near the bonding interface were formed respectively. Thereafter, Cr_2N transforms to CrN and the mixed phase with CrN, (Cr_3Si) and Ni- (Si) alloy were formed at bonding interface. The thickness of this mixed phase depend on the thickness of Cr-plating. After disappearance of Cr as a plating layr as a result of the formation of reaction layrs, Ni-Cr-Si ternary eutectic alloy of low melting temperature is formde by the another reaction with diffused Ni through the mixed phases to Si_3N_4, so that this alloy phase fuses and Si_3N_4 are aggressively attacked and CrN phases already formed aer decomposde. On the bonding at 1473K,the close condensed CrN phases including little Ni- (Si) alloy are formed at bonding interface, so that the formation of fused phases are suppressed. A similar close condensed CrN phases can form by using a previously annealed Cr-plating Ni sheet as a insert. As a result of this research, it was found that there is a possibility of higher grade heat-resisting bonding using a insert with dual layr plating of Ni and Cr on Mo plate.