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Surface durability studies on sintered low alloy steel gears
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Ferrous mechanical properties HIGH PERFORMANCE FERROUS PM MATERIALS UTILIZING HIGH TEMPERATURE SINTERING
J.A. Hammill et al, (Hoeganas Corp, Riverton, N e w Jersey, USA). The need for P M steels with higher strength and improved dynamic properties was discussed with respect to the high temperature sintering to attain these requirements. The properties of several grades of Fe base powders with alloy additions were investigated. Tensile, impact and fatigue properties were viewed. CYCLIC DEFORMATION BEHAVIOUR OF SINTERED P U R E AND ALLOYED IRON S. Klumpp et al, (University of Karlsruhe, Germany). A study of the effects of cyclic loading on deformation and microstructure of PM pure Fe, Fe-P, Fe-Cu and Fe-Cu-C alloys with densities in the range 6.8 to 7.6 g / c m 3 was reported. As a result of pores, inhomogeneous plastic deformation and p r e m a t u r e crack initiation and growth w e r e o b s e r v e d . C r a c k n u c l e a t i o n was always at pores and during cycling new cracks formed and there was crack growth because of coalescence of cracks. Plastic deformation became more homogeneous with increase in density. Additions of P, Cu or Cu and P were reported to increase the fatigue strength notably in materials with higher densities. HIGH CYCLE F A T I G U E BEHAVIOUR OF SINTERED STEELS A. Piotrowski and I.D. Eifler, (University of Essen, Germany). Results of fatigue tests on Fe, Fe-Cu and F e - C u - N i a l l o y s w e r e p r e s e n t e d for materials with densities in the range 6.2 to 7.2 g / c m z. Fatigue limits and cyclic stress/strain responses were determined a n d c h a n g e s in s u r f a c e t o p o g r a p h y observed and correlated with m i c r o s t r u c t u r e a n d cyclic d e f o r m a t i o n curves. Measurements of inhomogeneous stress distribution were made and
48 MPR November 1992
localized plastic deformation was found. Short term tests with continuously increasing stress amplitude were used to predict the fatigue limit of a range of P M steels. COPPER INFILTRATION OF WATER ATOMIZED POWDER COMPACTS
W.I~ Fricke, (Kobelco Metal Powder of America Inc, Seymour, Indiana, USA). Infiltration of Cu into Fe base compacts m a d e from water atomized powders was d i s c u s s e d as a f u n c t i o n of d e n s i t y , dimensional changes and 0 content. The effects of t h e s e factors and l u b r i c a n t content, sintering atmospheres and delubricating conditions were investigated. An outline of the tests carried out and the results obtained was presented. Optimum conditions for infiltration were identified.
Heat treatment EFFECT OF MATERIAL AND DENSITY ON IONITRIDING OF PM PARTS W. Rembges and W. Zimmerman, (Ringsdorf-Werke GmbH, Berlin, Germany). The effects of material and its density on hardness, c o m p o u n d s formed and case depths of ionitrided parts were studied. Problems in ionitriding steel of normal density were noted. Efforts of inhomogeneity and alloy elements were outlined. SURFACE HARDENING OF PM S T E E I ~ BY VACUUM AND GLOW DISCHARGE CARBURIZING M. Rosso et al, (Polytechnic of Turin, Turin,
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INFLUENCE OF PHOSPHORUS ON HF_~T AND THERMOCHEMICAL TREATMENT OF SINTERED STEELS
A. Molinari et al, (University of Trento, Trento, Italy). The role of P as a sintering enhancer was reviewed with regard to the improvements in properties arising from increased densification. The tendency of P to segregate at grain boundaries during thermal cycling was considered. Research into the effects of alternative thermal cycles for hardening and surface carburizing and nitriding of Fe-Mo-P and Fe-C-P alloys was described. It was confirmed that Fe alloys with P cannot be satisfactorily treated by conventional heat treatment procedures but modified thermal cycles can minimize segregation of P thus preserving the beneficial effects of P on properties of sintered and hardened parts.
Heavy alloys MICROSTRUCTURE MORPHOLOGY ASPECTS AND THE RELATIONSHIP TO MECHANICAL PROPERTIES OF HE~AVY ALLOYS TJ. McCabe and J. Mullendore (Metalworking Technology Inc, USA). The structure, W particles in a W-Ni-Fe matrix, of heavy alloys was discussed with respect to the effects of microstructure, alloy composition and processing history on the mechanical properties. Quantitative metallography was used in the study of microstructure/property relationships. W particle shape, particle contiguity and separation were considered. Tests on WNi-Fe and W-Ni-Co alloys were described.
Italy). The c a r b u r i z i n g of PM s t e e l s w a s discussed. Particular reference was given to low pressure processes, vacuum and plasma discharge carburizing using CH4 as the source of C for which carburizing rates are high and cases are of uniform depth. In the investigation described a range of PM steels were vacuum or plasma carburized to a d e p t h of 0.7 mm. H a r d n e s s e s w e r e m e a s u r e d and s t r u c t u r e s e x a m i n e d by optical and electron microscopy. Effects of process variables were e x a m i n e d using microhardness depth correlation.
PHYSICAL PROPERTIES WITH BINDER COMPOSITES IN 93% TUNGSTEN HEAVY ALLOYS H.S. Song et al, (Agency for Defence Developments, Korea). The effects of matrix composition in W7%(Ni, Fe) were investigated. Binder Ni contents of 70, 80 and 90% were studied. The o p t i m u m sintering temperature was reported to increase with Ni content which also increased the volume fraction of the
Ferrous mechanical properties HIGH PERFORMANCE FERROUS PM MATERIALS UTILIZING HIGH TEMPERATURE SINTERING
J.A. Hammill et al, (Hoeganas Corp, Riverton, N e w Jersey, USA). The need for P M steels with higher strength and improved dynamic properties was discussed with respect to the high temperature sintering to attain these requirements. The properties of several grades of Fe base powders with alloy additions were investigated. Tensile, impact and fatigue properties were viewed. CYCLIC DEFORMATION BEHAVIOUR OF SINTERED P U R E AND ALLOYED IRON S. Klumpp et al, (University of Karlsruhe, Germany). A study of the effects of cyclic loading on deformation and microstructure of PM pure Fe, Fe-P, Fe-Cu and Fe-Cu-C alloys with densities in the range 6.8 to 7.6 g / c m 3 was reported. As a result of pores, inhomogeneous plastic deformation and p r e m a t u r e crack initiation and growth w e r e o b s e r v e d . C r a c k n u c l e a t i o n was always at pores and during cycling new cracks formed and there was crack growth because of coalescence of cracks. Plastic deformation became more homogeneous with increase in density. Additions of P, Cu or Cu and P were reported to increase the fatigue strength notably in materials with higher densities. HIGH CYCLE F A T I G U E BEHAVIOUR OF SINTERED STEELS A. Piotrowski and I.D. Eifler, (University of Essen, Germany). Results of fatigue tests on Fe, Fe-Cu and F e - C u - N i a l l o y s w e r e p r e s e n t e d for materials with densities in the range 6.2 to 7.2 g / c m z. Fatigue limits and cyclic stress/strain responses were determined a n d c h a n g e s in s u r f a c e t o p o g r a p h y observed and correlated with m i c r o s t r u c t u r e a n d cyclic d e f o r m a t i o n curves. Measurements of inhomogeneous stress distribution were made and
48 MPR November 1992
localized plastic deformation was found. Short term tests with continuously increasing stress amplitude were used to predict the fatigue limit of a range of P M steels. COPPER INFILTRATION OF WATER ATOMIZED POWDER COMPACTS
W.I~ Fricke, (Kobelco Metal Powder of America Inc, Seymour, Indiana, USA). Infiltration of Cu into Fe base compacts m a d e from water atomized powders was d i s c u s s e d as a f u n c t i o n of d e n s i t y , dimensional changes and 0 content. The effects of t h e s e factors and l u b r i c a n t content, sintering atmospheres and delubricating conditions were investigated. An outline of the tests carried out and the results obtained was presented. Optimum conditions for infiltration were identified.
Heat treatment EFFECT OF MATERIAL AND DENSITY ON IONITRIDING OF PM PARTS W. Rembges and W. Zimmerman, (Ringsdorf-Werke GmbH, Berlin, Germany). The effects of material and its density on hardness, c o m p o u n d s formed and case depths of ionitrided parts were studied. Problems in ionitriding steel of normal density were noted. Efforts of inhomogeneity and alloy elements were outlined. SURFACE HARDENING OF PM S T E E I ~ BY VACUUM AND GLOW DISCHARGE CARBURIZING M. Rosso et al, (Polytechnic of Turin, Turin,
.
.
.
.
.
.
.
....
INFLUENCE OF PHOSPHORUS ON HF_~T AND THERMOCHEMICAL TREATMENT OF SINTERED STEELS
A. Molinari et al, (University of Trento, Trento, Italy). The role of P as a sintering enhancer was reviewed with regard to the improvements in properties arising from increased densification. The tendency of P to segregate at grain boundaries during thermal cycling was considered. Research into the effects of alternative thermal cycles for hardening and surface carburizing and nitriding of Fe-Mo-P and Fe-C-P alloys was described. It was confirmed that Fe alloys with P cannot be satisfactorily treated by conventional heat treatment procedures but modified thermal cycles can minimize segregation of P thus preserving the beneficial effects of P on properties of sintered and hardened parts.
Heavy alloys MICROSTRUCTURE MORPHOLOGY ASPECTS AND THE RELATIONSHIP TO MECHANICAL PROPERTIES OF HE~AVY ALLOYS TJ. McCabe and J. Mullendore (Metalworking Technology Inc, USA). The structure, W particles in a W-Ni-Fe matrix, of heavy alloys was discussed with respect to the effects of microstructure, alloy composition and processing history on the mechanical properties. Quantitative metallography was used in the study of microstructure/property relationships. W particle shape, particle contiguity and separation were considered. Tests on WNi-Fe and W-Ni-Co alloys were described.
Italy). The c a r b u r i z i n g of PM s t e e l s w a s discussed. Particular reference was given to low pressure processes, vacuum and plasma discharge carburizing using CH4 as the source of C for which carburizing rates are high and cases are of uniform depth. In the investigation described a range of PM steels were vacuum or plasma carburized to a d e p t h of 0.7 mm. H a r d n e s s e s w e r e m e a s u r e d and s t r u c t u r e s e x a m i n e d by optical and electron microscopy. Effects of process variables were e x a m i n e d using microhardness depth correlation.
PHYSICAL PROPERTIES WITH BINDER COMPOSITES IN 93% TUNGSTEN HEAVY ALLOYS H.S. Song et al, (Agency for Defence Developments, Korea). The effects of matrix composition in W7%(Ni, Fe) were investigated. Binder Ni contents of 70, 80 and 90% were studied. The o p t i m u m sintering temperature was reported to increase with Ni content which also increased the volume fraction of the