Measurement of saturation magnetization of cemented carbides and applications

Measurement of saturation magnetization of cemented carbides and applications

The conditions under which Al20 a is d e p o s i t e d , on a substrate for an AICI3/ H 2 / C O 2 gas mixture were investigated. In particular the eff...

132KB Sizes 0 Downloads 17 Views

The conditions under which Al20 a is d e p o s i t e d , on a substrate for an AICI3/ H 2 / C O 2 gas mixture were investigated. In particular the effect of the free gas volume a r o u n d t h e s u b s t r a t e was s t u d i e d . A theoretical characteristic dimension, L~ax, of the critical free gas volume is proposed and is defined as the m a x i m u m distance IYom the substrate where H20 molecules, formed in the gas reaction, cannot reach the s u r f a c e of t h e s u b s t r a t e . The dependence of Lma × on pressure, t e m p e r a t u r e a n d g a s flow r a t e s is d i s c u s s e d a n d is r e p o r t e d to be in agreemenl with the experimental data.

Electrical materials RARE EARTH E L E M E N T S AND ADVANCED FURNACE TECHNIQUES FOR P R O D U C T I O N OF PERMANENT MAGNETS M. Croker, (Torvac Furnaces Ltd, Hachenburg, Germany). Powder Metall Int, Vol 24, No 2, 1992, 106-109. The production and use of rare earth p e r m a n e n t m a g n e t s (REPM) and o t h e r m a t e r i a l s is reviewed w i t h r e s p e c t to magnetic properties. Design of sintering f u r n a c e s a n d p r o c e s s p r o c e d u r e s are d e s c r i b e d a n d d i s c u s s e d . Reference is made to ferrite materials, Al-Ni-Co, Sm-Co and R.E. -Fe-B alloys. A P P L I C A T I O N OF A POWDER C O A T I N G M E T H O D TO D I S P E R S I O N OF F I N E NICKEL POWDER INTO SILVERNICKEL ALLOY MATRIX

M. S a t o h et al, (University of Osaka, J a p a n ) , Powder Technology, Vol 70, No 1, 1992, 71-76. A m e t h o d for the coating of a gas atomized Ag-Ni powder (mean %Ni 4wt%, mean size 385 I~m with a fine Ni powder (0.02, 0.2, or 1.0 lam) is described. The c o n s o l i d a t e d m a t e r i a l s are for use as electrical contacts. A high s p e e d / h i g h s h e a r mill was u s e d to p r e p a r e t h e c o m p o s i t e p o w d e r and the s t a t e of dispersion of Ni in the composite was d e t e r m i n e d by control of t h e process. S t r u c t u r e s were a s s e s s e d by s c a n n i n g electron microscopy. The Ag-Ni contacts, with a three-dimensional network of fine Ni particles were reported to show improved performance in comparison with ordinary Ag-Ni contacts. E F F E C T OF MECHANICAL ALLOYING ( M A ) ON T H E M A G N E T I C P R O P E R T I E S OF SAMARIUM-IRON N I T R I D E MATERIALS M. Umemoto et al, (Toyohashi University of Technology, J a p a n ) . J J a p a n Soc Powder and Powder Metallurgy, Vol 38, No 7, 1991, 957-962. (In J a p a n e s e ) .

The use of MA to p r e p a r e Sm-Fe-N magnetic materials is described. Elemental powders were milled and the milled powders are reported to consist of ~Fe, an a m o r p h o u s Sm-Fe p h a s e and SmFe2 at %Sm above 26%. N was introduced by heat treatment. Effects of milling time on nitride formation was studied for the Fe-19% Sm alloy which was found to consist wholly of a m i x e d S m F e n i t r i d e . High v a l u e s o f coercivity are reported.

P R O P E R T I E S AND M I C R O S T R U C T U R E S OF S I N T E R E D SILVER-ZINC OXIDE ELECTRICAL CONTACT MATERIALS L. Yejian and F. Li, (Suzhou Alloy Material Factory, Suzhou, China), PM Technology, Vol 10, No 1, 1992, 44-48. (In Chinese). The p r o d u c t i o n of Ag-ZnO c o n t a c t m a t e r i a l s h a s b e e n i n v e s t i g a t e d . The e f f e c t s of p o w d e r p r e p a r a t i o n by m e c h a n i c a l m i x i n g a n d c h e m i c a l coprecipitation, variations in pressing and sintering conditions and other technological p a r a m e t e r s are described, t h e p e r f o r m a n c e o f t h e alloys w e r e investigated and it is reported t h a t the properties and durability can be optimized by use of chemical co-precipitation and the addition of 0.5% Ni.

Hard materials TITANIUM C A R B I D E / N I T R I D E AND ITS APPLICATIONS S.N. Bhat and R. Scinivasan, (Widia (India) Ltd., Bangalore, India), Trans Pm Assoc. of India, Vol 18, 1991, 57-62. A comparison is made of the structure p r o p e r t i e s and c u t t i n g p e r f o r m a n c e of cutting tools in which WC is partially replaced by varying a m o u n t s of TiC, TaC, NbC, TiN and Mo2C and the binder used is a mixture of Co and Ni. The performance of a TIC-TiN, as assessed by flank and crater wear, is reported to be better t h a t alloys without TIN. Coatings are also considered.

HEAT TREATMENT OF ELECTROLYTICALLY COATED CHROMIUM BORIDE-NICKEL C O M P O S I T E MATERIALS V.N. Yanesky et al. P o r o s h k o v a y a Metallurgiya, No 7, 1991, 49-53. (In Russian). Interactions, during annealing of Ni cemented CrB2 Ni, between Ni and CrB2 have been investigated by high t e m p e r a t u r e microscopy and the thermodynamic relations established. The transformation of CrB2 into NiaB is shown to proceed by the formation of ternary c o m p o u n d s CraNiB and Cr2NiB 2. The findings are confirmed by X-ray p h a s e and spectral analysis.

A L U M I N A C O A T E D C U T T I N G TOOL MATERIALS FOR E F F I C I E N T MACHINING

M. Tobioka et aI, ( S u m i t o m o Electric Hardmetal Ltd, Prince's Risborough, UK),

Int J Refactory Metals & Hard Materials, Vol 10, No 4, 1991, 211-218. The d e v e l o p m e n t of a c u t t i n g tool material in which an Al203 coating. 'ACE Coat AC15', is deposited on a c e m e n t e d carbide substrate, with a composition gradient between substrate and coating, is d e s c r i b e d . The c o m p o s i t e m a t e r i a l is reported to have improved resistance to breakage while retaining plastic d e f o r m a t i o n resistance, i n c r e a s e d w e a r resistance and cutting performance.

S I N T E R I N G OF SILICON-TITANIUMBORON DOPED DIAMOND

W. Tao et al, (University of Science and Technology, Beijing, China), PM Technology, Vol 10, No 1, 1992, 13-18 (In Chinese). The p a p e r describes investigations into the reactions occurring during the sintering of diamond, powder which had been d o p e d with Ti, Si or B. It is shown t h a t as the t e m p e r a t u r e increases TiC, SiC and TiSi2 are formed. At 1500 to 1600°C the TiSi2 decomposed into Ti and Si which then formed additional carbides. The d i a m o n d particles are reported to be bonded by the sintering of the carbides in the matrix.

M E A S U R E M E N T OF S A T U R A T I O N M A G N E T I Z A T I O N OF C E M E N T E D CARBIDES AND APPLICATIONS

W. Weixin, (Cemented Carbide Inst., Tianjin, China), PM Technology, Vol 10, No 1, 1992, 54-58. (In Chinese). M a g n e t i c s a t u r a t i o n of c e m e n t e d carbides have been measured and related to structure. The use of the m e a s u r e m e n t s for a s s e s s m e n t of quality is discussed and the relations between magnetic properties and composition and transverse rupture strength are considered.

C H A R A C T E R I Z A T I O N OF P O W D E R A N D HIP T15 TOOL S T E E L

A. Lawley et al, (Drexel University, Philadelphia, Pennsylvania, USA), Metallurgical Trans A, Vol 22A, No 11, 1991, 2733-2745 The effects of powder particle size on the s t r u c t u r e of gas atomized p o w d e r and c o n s o l i d a t e d T15 tool steel have been i n v e s t i g a t e d . The p o w d e r s h o w e d a s e g r e g a t e d s t r u c t u r e i r r e s p e c t i v e of particle size with MC and M2C carbides mainly at grain boundaries. The m a t r i x of the p o w d e r was a mixture of retained austenite and martensite. After consolidation the carbides are reported to

MPR July/August 1992 59