THE'APPLICATION OF RARE EARTHS IN HARD METALS

In order to investigate the influence of rare-earth elements on the properties of hard metals, the comparative tests for different R.E.elements (MM,Ce,Nd,La,Dy,Y), and different adding contents and adding in different hard metals,(WC-Co, WC-TiC-Co, WC-TaC-Co, WC-TiC-TaC-Co) have been studied under the conditions of conventional producing process of hard metals, Results show that the bending strength of hard metals at room temperature are obviously improved by the addition of R.E.elements. The maximum limit of improvement is achieved by an addition of 15.5% (YTl 5 + 0.2%MM), while hardness increases slightly (0.2-0.4HRA) or remains constant.
By using high magnification metallography it was found that the grain of carbide(including WC-TiC solid solution) in alloys became finer and more homogeneous after the addition of R.E. elements. The above effects were more obvious with increasing the content of the R.E.additives.
602 MM, 710MM rare- earth alloy cutting tools were compared with YG8, YG6X tools for finish machining TA6 titanium alloy and stainless steel parts.The life time of the former tools was 4-6 times longer than the later tools. The productivity was increased by over 2 times and the finished surface of work-pieces was obviously improved by using the former cutting tools.