Production of aluminium materials by spray deposition

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systems, notably Ni-Cd, Pb-acid, Li cells and Fe-air were considered to meet specific requirements.

of t h e disk. O t h e r friction p a i r s were c o n s i d e r e d for future use including A1 composite disc materials.

FRICTION MATERIALS -- A REVIEW

MANUFACTURING METHODS AND QUALITY CONTROL P R O C E D U R E S FOR THERMAL SPRAY POWDERS

I~D. L6cker, (Miba-Frictec, Vorchdorf, Austria). Metallic and n o n - m e t a l l i c friction materials for wet and dry running were reviewed w i t h r e g a r d to c o m p o s i t i o n , coefficients of friction, energy absorption, type of application such as brakes and clutches, t e m p e r a t u r e and environmental stability and the elimination of asbestos from compositions. Sintered metallic materials with non-metallic additives were included in the review. CHANGES CAUSED BY LEGISLATION AGAINST A S B E S T O S R. Baker, (Ferodo, Stockport, UK). Attention was drawn to the hazards to health posed by the use of asbestos which,~ in t h e p a s t , h a s b e e n a very useful constituent of friction materials and the consequent need to eliminate its use. The p a p e r w e n t on to d e s c r i b e efforts to substitute other, less hazardous, substances for asbestos. It was shown t h a t although some materials are good substitutes there was a significant cost penalty arising from their use. Costs could be reduced by mixing low and high cost m a t e r i a l s . A l t e r n a t i v e s to a s b e s t o s , including metallic materials, were discussed. FRICTION MATERIALS IN AEROSPACE APPLICATIONS T. Wells, (Dunlop Aviation, Coventry, UK). The f o r m u l a t i o n of s i n t e r e d friction materials, which contain abrasives, friction modifiers, lubricants and sintering aids in a m e t a l l i c m a t r i x , w a s d e s c r i b e d . The development of organic friction materials to replace these was discussed. The usual metallic matrix materials are Cu or Fe. Be has been used to a small e x t e n t to reduce weight for aerospace applications. The used of C-C composites was considered. FRICTION MATERIALS FOR USE IN RAIL TRANSPORT APPLICATIONS K.D. Dolbera, (Ferodo, Stockport, UK). The p a p e r traced the development of braking m a t e r i a l s for railway uses. In particular the d e v e l o p m e n t of d i s k / p a d friction pairs for use at high speed was discussed with regard to the need for dissipation of considerable quantities of energy as heat. Sintered metal p a d s were reported to have been successfully used in a n u m b e r of cases. The rigid n a t u r e of s i n t e r e d m e t a l p a d s h a s led to t h e d e v e l o p m e n t of low modulus conformable brake p a d s which a d a p t to the t o p o g r a p h y

62 MPR March 1992

C.R. Britton, (Metco Ltd., Woking, UK). The m e t h o d s u s e d to m a n u f a c t u r e metallic and non-metallic powders for use in coatings was discussed with reference to quality control and assurance. Each method, including spray drying, atomization and electric arc melting, was s h o w n to h a v e i t ' s own m e r i t s a n d limitations. The existence of a n u m b e r of novel m e t h o d s , sol-gel t e c h n i q u e s , cop r e c i p i t a t i o n a n d s p r a y pyrolysis, were noted. Quality factors, particle size and size distribution, chemical composition, including trace and impurity element control and powder morphology were discussed. THERMALLY SPRAYED COATINGS IN TRANSPORTATION APPLICATIONS P.m. Chandler, (Plasma-Technik, Newport, cg). A p p l i c a t i o n s for t h e r m a l l y s p r a y e d coatings on c o m p o n e n t s used in t r a n s p o r t were reviewed. A description of the process, involving the use of metallic or non-metallic powder, was given. The process can be carried out in air which gives coatings which have a few p e r c e n t porosity or in vacuum which reduces the porosity to less t h a n 0.5%. Coatings with a wide range of compositions are possible. An outline of possible future trends, including sprayed coatings of metal m a t r i x composites, was presented. COATED N E O D U R E (IRONNEODYMIUM-BORON) MAGNETS P. Mitchell, (Philips Components, Southport, UK). Attention was drawn to the s u s c e p t i b i l i t y to c o r r o s i o n of Fe-Nd-B magnets and to the need for protective coatings of types d e t e r m i n e d by service requirements. A n u m b e r of coatings, A1 chromate, Ni, TiN, cathodically deposited p a i n t and d u p l e x coatings with two or more of these were reviewed. PLASMA SPRAYED COATINGS K.T. Scott, (AEA Industrial Technology, Didcot, UK). The process of p l a s m a spraying was described with emphasis on the requirements of the powder used and the properties of the coatings. Application of p l a s m a s p r a y e d c e r a m i c c o a t i n g s in t r a n s p o r t use were described. The use of p l a s m a spraying as a technique for nearnet-shape fabrication was discussed.

ROLE OF HARDMETALS IN TRANSPORTATION R. Edwards. The role of h a r d m e t a l s in the p r o d u c t i o n of components for transportation applications was discussed with regard to t h e cutting a n d forming of parts. The limited use of h a r d m e t a l s as c o m p o n e n t s was noted and this was attributed to high cost and p a r t weight. ALLOYS FOR TRANSPORTATION SYSTEMS I.C. Elliot, (Inco Alloys Ltd, Hereford, UK). The use of PM in the production of parts for t r a n s p o r t systems was reviewed with regard to t h e need for high integrity, particularly for aero engine parts. The use of m e c h a n i c a l alloying w a s d i s c u s s e d . E x a m p l e s were given to i l l u s t r a t e t h e r e q u i r e m e n t s for consistent, defect free material which is delivered on a j u s t in time basis. PRODUCTION OF ALUMINIUM MATERIALS BY SPRAY DEPOSITION J. White and J.C. Willis, (Alcan International Ltd, Banbury, UK). The use of spray deposition to produce Al alloys and Al-base MMC was discussed from the point of view of the improvements in mechanical properties arising from RS. The process was r e p o r t e d to give greater production rates t h a n conventional PM. A1Cu-Mg and Al-Li alloys, a m o n g s t others, w e r e s h o w n to b e n e f i t f r o m t h e RS treatment. In the case of MMCs it was shown to be possible to incorporate up to 20% SiC p a r t i c l e s into an Al alloy. A s u m m a r y of p r o p e r t y i m p r o v e m e n t s for individual alloys and MMCs was given. E F F E C T S OF ALUMINA FIBRE CONTENT ON P R O P E R T I E S OF A PM ALUMINIUM ALLOY 6061 J.W. Kaczmar and I~U. Kainer (Technische Universit~it, Clausthal-Zellerfeld, Germany). An Al alloy 6061 with 5A120:~ fibre was made by wet blending alloy powder with the fibre, consolidated by hot extrusion and heat treated. Densities of 97.5 and 99.3% w e r e a t t a i n e d w i t h 30 a n d l 0 vol% respectively. Structure and properties were reported. The PM materials were c o m p a r e d with squeeze cast preforms. POWDERS AND P R O C E S S E S FOR HIGH PERFORMANCE PM S T E E L S U. EngstrSm et al, (HSgan~ism, Sweden). Some high s t r e n g t h alloys a n d t h e effects of process parameters on dimensional tolerances were described. It was shown t h a t to meet the requirements of new applications it was necessary to use diffusion alloyed powders and prealloyed