Effects of niobium addition on microstructure and properties of CPM121 powder metallurgy high-speed steel  

铌的添加对CPM121粉末冶金高速钢组织和性能的影响

作　　者：ZHANG Qian-kun LI Su-wang XIAO Yi-feng WU Liang QIAN Jin-wen CHEN Ze-min SHEN Wei-jun LIN Nan HE Yue-hui 张乾坤;李苏望;肖逸锋;吴靓;钱锦文;陈泽民;沈玮俊;吝楠;贺跃辉(School of Mechanical Engineering,Xiangtan University,Xiangtan 411105,China;State Key Laboratory of Powder Metallurgy,Central South University,Changsha 410083,China;College of Materials Science and Engineering,Hunan University,Changsha 410082,China)

机构地区：[1]School of Mechanical Engineering,Xiangtan University,Xiangtan 411105,China [2]State Key Laboratory of Powder Metallurgy,Central South University,Changsha 410083,China [3]College of Materials Science and Engineering,Hunan University,Changsha 410082,China

出　　处：《Journal of Central South University》2021年第4期1206-1218,共13页中南大学学报（英文版）

基　　金：Projects(51771237,51704257)supported by the National Natural Science Foundation of China;Project(2019JJ60019)supported by the Joint Fund of Hunan Province,China;Project(17QDZ25)supported by the School Level Fund of Xiangtan University,China。

摘　　要：Massive vanadium additions as hard phases in powder metallurgy high-speed steels(PM HSS)lead to higher cost and bad machinability.In this study,ultrahigh alloy PM HSS with CPM121(10W-5Mo-4Cr-10V-9Co,wt.%)as the basic composition,was directly compacted and activation sintered with near-full density(>99.0%)using pre-oxidized and ball-mixed element and carbide powders.Niobium-alloyed steels(w(V)+w(Nb)=10 wt.%)show higher hardness and wear resistance,superior secondary-hardening ability and temper resistance.But excess niobium addition(>5 wt.%)leads to coarsened carbides and deteriorated toughness.EPMA results proved that niobium tends to distribute in MC carbides and forces element W to form M6C and WC carbides.Further,the role of rotary forging on properties of niobium-alloyed steels(S3)was researched.After rotary forging with deformation of 40%,the bending strength and fracture toughness of niobium-alloyed steels could be further improved by 20.74%and 43.86%compared with those of sample S3 without rotary forging,respectively.超高钒粉末冶金高速钢通常存在加工困难、生产成本高的问题。研究以超高合金粉末高速钢CPM121(10W-5Mo-4Cr-10V-9Co,wt.%)作为基础成分,采用元素和碳化物的预氧化球磨混合粉为原料,经压制、活化烧结制得致密化(>99.0%)的样品,研究铌的添加(w(V)+w(Nb)=10 wt.%)对CPM121粉末冶金高速钢组织和性能的影响。结果表明:铌强化高速钢表现出较高的硬度及耐磨性、优异的二次硬化性能和抗回火性。但当铌含量超过5%时则会导致组织中碳化物的粗化和偏聚现象,进而导致材料的强韧性降低。EPMA结果表明铌是MC碳化物的形成元素,促使大量W在M6C及WC碳化物中聚集。其次,旋锻变形可以大幅度提高材料的强韧性,成分为S3(3%Nb+7%V)的CPM121铌高速钢在40%的变形量下,材料的抗弯强度和冲击韧性相较于未旋锻态分别提高了20.74%和43.86%。

关 键 词：CPM121 niobium-alloying microstructure mechanical properties temper resistance wear resistance rotary forging powder metallurgy 

分 类 号：TG142.1[一般工业技术—材料科学与工程]