Nitrocarburizing of sintered steels

Nitrocarburizing of sintered steels

Review MATERIALS ASPECTS OF FATIGUE BEHAVIOUR OF PM STEELS P Engdahl, et al, (Hoganas AB, Sweden). Vol 2, Paper 29, 144-154. The paper describes the d...

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Review MATERIALS ASPECTS OF FATIGUE BEHAVIOUR OF PM STEELS P Engdahl, et al, (Hoganas AB, Sweden). Vol 2, Paper 29, 144-154. The paper describes the different fatigue behaviour of heterogeneous and homogeneous material structures as well as the differences between materials based on sponge and water atomized powders. Fatigue strengths of high temperature PM steels, with 0.5-1.0%C, produced from partially prealloyed powders, are reported.

Alloy compositions and process variables of potential high strength sintered steels were investigated with regard to properties of finished parts and cost minimization. Two steels, Fe-4%Ni- 1.5%Cu-0.5%Mo-0.5%C and Fe-0.2%Mo- 1%Cr-0.8%Mn-0.5%C were studied. The steels have superior properties compared with Fe-Cu-C steel.

PROCESSES INVOLVED DURING PRODUCTION OF PM Fe-Mo ALLOYS A Boulama, et al, (University of Paris, France). Wol 2, Paper 39,222-228.

A Mo-ALLOYED PM STEEL FOR SURFACE HARDENING B Lindqvist, (Hoganas AB, Sweden). Vol 2, Paper 32, 170-177.

The paper deals with a prealloyed 1.5%Mo steel powder developed to overcome problems encountered in surface heat treatment of PM steels. Comparisons are made with other powders produced by prealloying and diffusion alloying techniques. It is concluded that the 1.5%Mo p o w d e r has high compressibility, small dimensional change during sintering, good hardenability and is suitable for carburizing and plasma-nitriding. Addition of l%Cu to 1.5%Mo steel gives tensile strength above 550MPa and hardness above 200 Vickers. EFFECT OF POROSITY ON ELASTIC CONSTANTS OF SINTERED ATOMIZED Fe R Haynes, J T Egediege, (Loughborough University of Technology, Loughborough, UK). Vol 2, Paper 33, 178-183. Elastic constants of sintered Fe containing 3-30% porosity have been measured by an ultrasonic technique. Porosity causes the modulus to fall sharply. The rate of reduction of the modulus decreases as porosity increases above 20%. Poisson's ratio decreases slowly up to 12% porosity but more rapidly at 15-20% porosity. The changes are attributed to changes in elastic deformation mechanisms. DEVELOPMENT OF HIGH STRENGTH SINTERED STEELS

N Motooka, et al, (Sumitomo Electric Industries Ltd, Itami, Japan). Vol 2, Paper 38, 217-221.

MPR November 1990

Improved sintering of Fe by Mo above A3 is balanced by the formation of intermetallic compounds when Mo content exceeds 20%. Secondary porosity is also noted due to the Kirkendall effect. Residual porosity is reduced for Mo content less than 10%.

RECYCLING SCRAP FERROUS POWDERS INTO HIGH STRENGTH STEEL S V Illango, P Ramaklishnan, (Indian Institute of Technology, Bombay, India). Vol 1, Paper 40, 229-233. An attempt is reported to recycle metal scrap by a PM route using high temperature sintering. The effects of sintering parameters on properties of sintered steels produced from recycled cast iron powders are investigated. Production of steels with tensile strength up to 850MPa and elongation of 5.6% is reported.

HIGH IMPACT AND TENSILE STRENGTH PM B-STEEL BY Cu INFILTRATION D F Berry, et al, (SCM Metal Products Inc, Cleveland, USA). Vol 2, Paper 45,255-258. Improved mechanical properties are claimed for Cu-infiltrated B-steel produced by a new, patented process. Charpy V-notch impact e n e r g i e s ( 8 - 3 O J ) and y i e l d s t r e n g t h (415-1450MPa), approaching those of low alloy cast steel have been recorded. These improved properties are said to enable PM material to replace cast or wrought steel components.

CORROSION RESISTANCE OF SINTERED AUSTEN1TIC STAINLESS STEEL L Fedrizzi, et al, (University of Trento, Italy). Vol 2, Paper 58,319-324. The corrosion of sintered 316L stainless steel containing up to 20%Cu was studied. The corrosion behaviour was similar to that of wrought stainless steel. The effects of variations in composition and processing parameters was investigated in an attempt to improve corrosion resistance.

NITROCARBURIZING OF SINTERED STEELS M Rosso, et al, (Department of Materials Science, Polytechnic of Turin, Italy). Vol 2, Paper 59,325-330. Sintered Fe and steel samples, containing Cr, Ni, AI and Mo were carbonitrided at 570"C for up to 1 hour in a NH3 (85%)/CH3OH(15%) atmosphere. The layers produced were examined microscopically, by microhardness profiling and X-ray analysis. Phases detected included e FeCN and T' Fe4N.

MACHINABILITY OF SINTERED STEELS P J James, (Loughborough University of Technology, Loughborough, UK). Vol 2, Paper 62,339-342. Machinability of some steel samples was assessed by use of a drilling test with HSS drills. Compacts were pressed and sintered to densities of 6.0 and 6.2gm/cm 3. The effects of MnS additions was studied. The cutting variables investigated were drilling speed, feed rate, drill geometry, thrust force and torque. Test results are given.


L L e d o u x , et al, ( A l l i a g e s F r i t t e s METAFRAM, Beauchamp, France). Vol 2, Paper 65,353-358. A study is reported of the effects of steam treatment on microstructure and static and fatigue properties of sintered Fe. Steam treatment was found to increase fatigue limit