无损鉴定WC-Co硬质合金显微结构参数的物理基础

Physical Basis of Nondestructive Evaluation on Microstructure Parameters in Cemented Carbides WC-Co

根据γ相磁性分析法用物理性能测定数据进行计算或用体视金相学技术直接测定γ相平均自由程,所得真实γ相平均自由程λ和通称γ相平均自由程λγ的关系规律一致。依据λ和λγ的关系确定了γ相平均自由程λ或WC晶粒邻接度CWC分别与γ相体积分数fγ和WC平均晶粒尺寸LWC的试验关系。阐明了用物理性能测定取代体视学测量无损鉴定WC-Co硬质合金显微结构参数的物理基础。结果表明:两相WC-Co合金的显微结构特征可用两个基本参数fγ和LWC确定;fγ和LWC分别主要取决于合金的钴配量和原料WC粉末平均颗粒尺寸,并在液相烧结过程中受γ相成分的制约;延长烧结时间将加剧LWC的长大程度,但不影响fγ的数量;烧结过程中fγ的增量和LWC的长大程度分别随合金碳含量的改变呈反向和正向变化,因而烧结过程中fγ的增加无助于WC晶粒尺寸的长大。

The consistent numerical value relationship regularity between the trueγ-phase mean free pathλand the nominalγ-phase mean free pathλγwas deduced by means of both calculating physical property measured data with theγ-phase magnetism analysis and measuring directlyγ-phase mean free path with stereo-metallographic technique.The respective relationships of theγ-phase mean free pathλor the WC-grain contiguity CWC with the elemental parametersγ-phase volume fraction fγand WC mean grain size LWC were deduced from the relation betweenλandλγ.The physical basis evaluating nondestructively microstructure parameters in cemented carbides WC-Co by use of to replace stereo-metallographic test by physical property measurement was expounded.The results showed that the microstructure feature of two-phase WC-Co alloy could determined by the two basic parameters fγand LWC;fγand LWCwere respectively determined by cobalt content and WC mean partical size in raw material and were restricted byγ-phase composition under sintering;the LWCgrowth degree bore a positive-going relation to sintering time,but the fγvalue bore no relation to sintering time;the fγincrement and the LWCgrowth degree bore opposite-going and positive-going relation to the carbon content increment in alloy respectively,so the fγincrement was helpless to the WC grain size growth by recrystallization under sintering.