Study On The Surfare Contained Coalt Super-hard High Speed Steel Of 20Cr2V2

Superhard high speed steel,as a kind of high speed steel with temperature hardness over HRC67,due to wear resistance,hot resistance,high hardness and so on,had become a very important material for processing hard cutting tools,producing numerical control machine tools and high speed cutting tools.In industry developed country,the output of cobalt-superhard high speed steel has already reached twenty percent of high speed steel's.However,the price of cobalt was very expensive in market and cobalt was short in our country,so this kind of speed steel was seldom made.The surface metallurgy HSS could be made on the surface of common carton steel or low alloy steel by a kind of advanced surface metallurgy technology.After alloying W,Mo,C and so on on the substrate,then by quenching and tempering process,the surface could got HSS'S composition and properties.Because of adequately making use of the surface's high hardness,anti-temper softening ability, wear resistance and the substrate's excellent toughness,this kind of surface metallurgy HSS was the best abilities combine.Besides,the price would be greatly gone down. This article presented a new method to produce a layer of super-hard high speed steel on the surface of low alloy steel by double glow plasma alloying technique.First, W-Mo-Co permeation was discussed on the surface of low alloy steel 20Cr2V2 and certain alloy elements was got;then the suface alloy component was close to supe-rhard high speed steel by following carburizing process;after quenching and tempering process,the alloying layer may possessed super HSS'excellent abilities.At last,the paper was mainly introduced that the wear resistance comparative experiments among W-Mo-Co permeation surface super-hard HSS and surface intensifying GCr15 steel.In the paper the following results had been achieved:1.Another new process of preparing contained cobalt super-hard surface HSS was achieved on the basis of tungsten molybdenum surface HSS by double glow plasma alloying technique,which perfected the double glow surface metallurgy technology,broadened the applying fields and would be more suitable for industry application.2.The composition of molybdenum reached 6 wt%and that of cobalt was about 12.5wt%and that of tungsten was about 11wt%after W-Mo-Co permeation on the surface of low alloy steel 20Cr2V2.In addition,the layer was metallurgical bonded with substrate and its column grain structure also had certain phase relation with substrate.3.After solid carburizing,the contents of carbide reached above 1.2wt%inside 75μm of W-Mo-Co alloying layer and surpassed the balance carbon value. 4.After hardening,the highest surface hardness reached 1200HV(above 70 HRC)and was graded distribution.At about 100μm from the surface,the hardness still reached 942HV(above 67HRC),so the alloyed layer satisfied the hardness standard of super-hard high speed steel.Besides,at 625℃,the hot hardness could reached 856HV(65HRC)and surpassed the hot hardness of contained cobalt super HSS M42(59HRC)and Co5(62.2HRC).So the surface contained cobalt super HSS had better tempering resistance stability.5.The main carbide styles and intermatallic compounds of W-Mo-Co permeation surface compound intensifying treatment were MC(?)M₂C(?)M₆C(?)Cr₇C₃ Co₃W and Fe₇Mo₃.6.The wear resistance of low alloy steel 20Cr2V2 after W-Mo-Co permeation surface compound intensifying treatments was excellent compare to low alloy steel 20Cr2V2 intensifying treatments.In contrast,the surface compound intensified specimen recorded a lower friction coefficient and the surface almost was not worn.However,the surface was covered a large number of substance from the worn steel ball,so the wear loss,wear ratio and wear velocity were negative reflected excellent performance of wear resistance.