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Localized corrosion of PM Stellite-6 in chloride environments
Powder production MEASUREMENT AND ANALYSIS METAL FLOW RATE IN GAS ATOMIZATION
OF
H.Henein et al. (University of Alberta, Edmonton, Canada.) Int. J. Powder Metall., Vol 35, No 1, 1999,51-59. Metal mass ratio, in gas atomization, is discussed. It is shown that if this can be controlled the powder would be more uniform and mean particle size more predictable. Gas flow is easy to measure but metal flow rate is less so. A new method of measurement is described. Molten metal height is measured and recorded. Friction loss in the delivery system is calculated. It is shown that integrity and cleanliness are important in maintaining a stable metal feed.
Fundamentals MODEL FOR UNIAXIAL COMPACTION OF CERAMIC POWDERS
C.H.Park et al. (National University, Seoul, Korea.) Powder Metall., Vol 42, No 3, 1999,269-274. A yield criterion is proposed for modelling of uniaxial compaction of ceramic powders using continuum mechanics. Three parameters characterize geometric hardening of the powder compact and the strength of the base material. The model was applied to three powders with differing particle size distribution, particle morphology and material base properties. Parameters were determined experimentally. Compaction was analysed by finite element calculation. ANALYSIS OF POWER DRAW IN BALL MILLS BY DISCRETE ELEMENT METHOD
A.Datta et al. (University of Utah, Salt Metall. Lake City, USA.) Canadian Quart., Vol 38, No 2, 1999, 133-140. Energy consumption in ball mills is discussed. It is shown that the power draft can be predicted from analysis of motions in the charge. This is simulated by a discrete element technique and position and velocities of balls can be calculated. Simulated and experimental results are compared. Power draft predictions, as functions of a few variables, are shown. The method is shown to be applicable to mixed ball size.
36 MPR September
2000
Sin tering
bon and steel
SINTERING ABNORMAL
PLASMA NITRIDING OF SINTERED IRON-CHROMIUM-MOLYBDENUM STEELS
OF IRON WITH GLOW DISCHARGE
J.L.R. Muzart et al. (Federal University of St Caterina, Florianopolis, Brazil.) Int. J Powder Metall., Vol34, No 8,1998, 55-62. It is reported that metallic powders had been sintered by heating in an abnormal Ar-20%H glow discharge. The sample to be sintered is the cathode and is heated by bombardment by ions and fast neutral atoms. The method is shown to be a cost effective means of sintering in a non-oxidizing atmosphere. Temperatures above 1300°C were attained but the container wall did not exceed 80°C. The process gave plasma sintering which resulted in low surface porosity due to sputtering effects. PROCESSING OF TITANIUM NET SHAPES BY SELECTIVE LASER SINTERING AND HIP
S.Das et al. Mater. Des., Vol 20, No 213, 1999, 115-121. Combination of selective laser sintering with HIP is discussed. It is shown that selective laser sintering can produce complex shaped parts with a gas tight skin. This is followed by containerless HIP to full density. The advantages of the combined processes are described. Use for Ni base superalloys and Ti-Al-V is reported. A Ti-6%Al-4%V alloy part is evaluated.
Cobalt LOCALIZED CORROSION OF PM STELLITE-6 IN CHLORIDE ENVIRONMENTS
A.E.Nessef University,
et al. Canal (Suez Port Said, Egypt.) 2. Metallkd., Vol90, No 3, 1999, 195-201. Pitting corrosion of Stellite-6, in 3%NaCl solution at ambient temperature, was investigated on a range of materials. HIP materials had the highest resistance to pitting. The critical crevice temperature is shown to be above ambient. Solutions of pH 1.5 and 3.0 crevice caused corrosion. Electrochemical findings are supported by scanning electron microscopy of corroded surfaces.
A.Molinari et al. (University of Trento, Trento, Italy.) Powder Metall., Vol42, No 2,1999,119-125. Fe-(1.5 or 3)%Mo-Cr and Fe-cl.5 or S)%Mo-Cr-C steels, with different microstuctures, were plasma nitrided. Cr allows formation of a hard diffusion layer irrespective of initial microstructure. Wear and impact tests were carried out and comparison is made between quenched and stress relieved samples. It is suggested that the methods could be used for parts subjected to fatigue. PROPERTIES OF NITROGEN ALLOYED STAINLESS STEELS
R.Tandon et al. (Philips Powder Metal Moulding, Menomonie, Wisconsin, USA.) Znt. J. Powder Metall., Vol 34, No 8, 1998,47-54. It is reported that by infusion of N into stainless steel during processing the yield and tensile strengths and corrosion resistance are improved without loss of ductility. Two steels, Fe-lS%Cr5%Mn-5%Ni-3%Mo-O.O14%C and 316L were investigated. N contents of 0.52% were attained. Injection moulding and catalytic debinding were used to make tensile test specimens. Comparison was made with a wrought steel with 0.69%N and conventional 316L steel. IMPROVEMENT OF FATIGUE PROPERTIES OF PM STEELS BY SHOT PEENING
S.Saritas et al. (Gazi University, Ankara, Turkey.) Powder Metall., Vol 42, No 2, 1999, 126-130. Fe-2%Cu-0.5%C steel was shot peened to improve fatigue properties and compared with shot peened Fe, Fe2%>Cu and Fe-O.S%C. Optimum shot peening conditions were established. Fatigue strength was increased by 31% for Fe, by 48% for Fe-C, 46% for Fe-Cu and 38% for Fe-Cu-C. It is concluded that both shot peening and alloy elements contribute to increased fatigue strength. SINTERING
OF CARBON
ATMOSPHERES PRACTICAL
STEELS -
EQUIPMENT
RESULTS
AND
OF
H.Henein et al. (University of Alberta, Edmonton, Canada.) Int. J. Powder Metall., Vol 35, No 1, 1999,51-59. Metal mass ratio, in gas atomization, is discussed. It is shown that if this can be controlled the powder would be more uniform and mean particle size more predictable. Gas flow is easy to measure but metal flow rate is less so. A new method of measurement is described. Molten metal height is measured and recorded. Friction loss in the delivery system is calculated. It is shown that integrity and cleanliness are important in maintaining a stable metal feed.
Fundamentals MODEL FOR UNIAXIAL COMPACTION OF CERAMIC POWDERS
C.H.Park et al. (National University, Seoul, Korea.) Powder Metall., Vol 42, No 3, 1999,269-274. A yield criterion is proposed for modelling of uniaxial compaction of ceramic powders using continuum mechanics. Three parameters characterize geometric hardening of the powder compact and the strength of the base material. The model was applied to three powders with differing particle size distribution, particle morphology and material base properties. Parameters were determined experimentally. Compaction was analysed by finite element calculation. ANALYSIS OF POWER DRAW IN BALL MILLS BY DISCRETE ELEMENT METHOD
A.Datta et al. (University of Utah, Salt Metall. Lake City, USA.) Canadian Quart., Vol 38, No 2, 1999, 133-140. Energy consumption in ball mills is discussed. It is shown that the power draft can be predicted from analysis of motions in the charge. This is simulated by a discrete element technique and position and velocities of balls can be calculated. Simulated and experimental results are compared. Power draft predictions, as functions of a few variables, are shown. The method is shown to be applicable to mixed ball size.
36 MPR September
2000
Sin tering
bon and steel
SINTERING ABNORMAL
PLASMA NITRIDING OF SINTERED IRON-CHROMIUM-MOLYBDENUM STEELS
OF IRON WITH GLOW DISCHARGE
J.L.R. Muzart et al. (Federal University of St Caterina, Florianopolis, Brazil.) Int. J Powder Metall., Vol34, No 8,1998, 55-62. It is reported that metallic powders had been sintered by heating in an abnormal Ar-20%H glow discharge. The sample to be sintered is the cathode and is heated by bombardment by ions and fast neutral atoms. The method is shown to be a cost effective means of sintering in a non-oxidizing atmosphere. Temperatures above 1300°C were attained but the container wall did not exceed 80°C. The process gave plasma sintering which resulted in low surface porosity due to sputtering effects. PROCESSING OF TITANIUM NET SHAPES BY SELECTIVE LASER SINTERING AND HIP
S.Das et al. Mater. Des., Vol 20, No 213, 1999, 115-121. Combination of selective laser sintering with HIP is discussed. It is shown that selective laser sintering can produce complex shaped parts with a gas tight skin. This is followed by containerless HIP to full density. The advantages of the combined processes are described. Use for Ni base superalloys and Ti-Al-V is reported. A Ti-6%Al-4%V alloy part is evaluated.
Cobalt LOCALIZED CORROSION OF PM STELLITE-6 IN CHLORIDE ENVIRONMENTS
A.E.Nessef University,
et al. Canal (Suez Port Said, Egypt.) 2. Metallkd., Vol90, No 3, 1999, 195-201. Pitting corrosion of Stellite-6, in 3%NaCl solution at ambient temperature, was investigated on a range of materials. HIP materials had the highest resistance to pitting. The critical crevice temperature is shown to be above ambient. Solutions of pH 1.5 and 3.0 crevice caused corrosion. Electrochemical findings are supported by scanning electron microscopy of corroded surfaces.
A.Molinari et al. (University of Trento, Trento, Italy.) Powder Metall., Vol42, No 2,1999,119-125. Fe-(1.5 or 3)%Mo-Cr and Fe-cl.5 or S)%Mo-Cr-C steels, with different microstuctures, were plasma nitrided. Cr allows formation of a hard diffusion layer irrespective of initial microstructure. Wear and impact tests were carried out and comparison is made between quenched and stress relieved samples. It is suggested that the methods could be used for parts subjected to fatigue. PROPERTIES OF NITROGEN ALLOYED STAINLESS STEELS
R.Tandon et al. (Philips Powder Metal Moulding, Menomonie, Wisconsin, USA.) Znt. J. Powder Metall., Vol 34, No 8, 1998,47-54. It is reported that by infusion of N into stainless steel during processing the yield and tensile strengths and corrosion resistance are improved without loss of ductility. Two steels, Fe-lS%Cr5%Mn-5%Ni-3%Mo-O.O14%C and 316L were investigated. N contents of 0.52% were attained. Injection moulding and catalytic debinding were used to make tensile test specimens. Comparison was made with a wrought steel with 0.69%N and conventional 316L steel. IMPROVEMENT OF FATIGUE PROPERTIES OF PM STEELS BY SHOT PEENING
S.Saritas et al. (Gazi University, Ankara, Turkey.) Powder Metall., Vol 42, No 2, 1999, 126-130. Fe-2%Cu-0.5%C steel was shot peened to improve fatigue properties and compared with shot peened Fe, Fe2%>Cu and Fe-O.S%C. Optimum shot peening conditions were established. Fatigue strength was increased by 31% for Fe, by 48% for Fe-C, 46% for Fe-Cu and 38% for Fe-Cu-C. It is concluded that both shot peening and alloy elements contribute to increased fatigue strength. SINTERING
OF CARBON
ATMOSPHERES PRACTICAL
STEELS -
EQUIPMENT
RESULTS
AND