镍含量对Co-8.8Al-9.8W合金中γ′相高温粗化的影响

为了研究镍含量对Co-Al-W高温合金中γ′强化相高温粗化的影响,采用场发射SEM观察、图像分析等方法对不同镍含量(5%、15%、25%、35%(原子分数))Co-8.8Al-9.8W基高温合金在1 000℃下经5h、10h、15h和25h时效处理后,合金中γ′相形貌的演变及粗化行为进行研究。结果表明,延长时效时间,γ′相快速长大,体积分数逐渐减小。当Ni含量为5%和15%时,时效时间为10h,γ′相基本溶解消失;当Ni含量为25%和35%时,γ′相形貌随着时效时间的延长从最初的立方状转变为不规则形状,最后趋于圆球状,γ′相尺寸也随之增加。此时,γ′相的粗化行为符合LSW粗化理论。25Ni合金的粗化速率明显高于35Ni合金的粗化速率。

Microstructure and microhardness of Co-8.8Al-9.8W superalloy cladding layer with different boron content

TIG welding was used to deposit Co-8.8 Al-9.8 W-0.2 B superalloy on 304 austenite stainless steel. The form factor of weld, dilution ratio, microhardness, microstructure and distribution of alloying elements were investigated. The microstructure of cladding layer was mainly hypoeutectic. The primary phases were cobalt-rich solid solution. The eutectic phase was composed of cobalt-rich solid solution,Co6W6C and Co Cx. When the boron content increased from 0.2% to 0.5%,the dilution ratio decreased,the primary phase became coarse and the microhardness decreased. When the boron content was from 0.5% to 2%,the dilution ratio and microhardness increased obviously,but the primary phase was refined.The hard phase of Co-8.8 Al-9.8 W became refined and the amount was raised,and the performance of cladding layer was improved with appropriate boron increase.