that the TiN powder had a high purity which contained no carbon (see Fig.2, a)and other metallic elements except titanium. If the TiN powder did not decompose in the liquid metal during the VIM process,it would remain its original size and morphology in the VIM ingot, being the large inclusion.However,by observing the samples of the VIM ingot carefully,we have not found the original TiN powder in them,although the nitrogen content of the ingot is about 240 ppm higher than that of the original forging bar. Table 1 The Nitrogen Contents of Original Forging Bar and VIM Ingot (ppm) Alloy Forging Bar TiN Added Nitrogen Added VIM Ingot GH169 (1n-718) 96 2000 453 336 GH132 (A-286) 44 2000 453 280 10 10818初BPC Fig.1 Morphology of pure TiN powder (a)and Inclusions in the VIM Ingot of GH169 (In-718)(b)(um) The investigation result shows that the average size of inclusions in the VIM ingot for both GH169 and GH132 is about 2um smaller than that in the original forging bar,but the quantity larger and a number of inclusion clusters,consis- Table 2 The Composition of Inclusions in the VIM Ingot of GH169 (In-718),wt% Inclusion Ti Nb Fe Ni Cr 1008-1 6.85 72.13 4.01 11.44 5.56 2 32.17 16.10 19.38 29.21 12.14 3 53.75 12.07 7.12 17.00 9.26 -4 48.49 30.12 4.36 10.86 6.10 503了 一 ， 。 ， ， · ， ， ， 一 一 一 笋 黔 霎 澳 羚滁聋 李 蠢 毕 、 参 纂 粉 、 牛 穷 髦移 娜酬 一 拼 拼 ， ， 一 一 ， 目二，上口，比 任丹﹄八 … 七丹乙户 上 一 一 一 一 。 。 。 。 。 。 口口上， 曰