Corrosion resistance of sintered stainless steels and effect of sulphoxidation

Corrosion resistance of sintered stainless steels and effect of sulphoxidation

SINTERING ADDITIVE FOR LIQUID PAHSE SINTERING OF AUSTENITIC STAINLESS STEEL SK. Jensen, E. Maahn (Technical University of Denmark, Lyngby, Denmark.) S...

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SINTERING ADDITIVE FOR LIQUID PAHSE SINTERING OF AUSTENITIC STAINLESS STEEL SK. Jensen, E. Maahn (Technical University of Denmark, Lyngby, Denmark.) Sintering enhancers for stainless steel were discussed. R was considered to be a sub-standard sintering enhancer due to formation of different borides and depletion of Cr. The composition of the new additive was calculated from thermodynamic data to give better properties to 3 16L stainless steel. Structure and properties were compared with conventional sintered 316L stainless steel. SENSITISATION PHENOMENA IN STAINLESS STEELS T. Mathiesen, E. Maahn (Technical University of Denmark, Lyngby, Denmark) An investigation of sensitization, or development of Cr depleted zones, which reduce corrosion resistance, in stainless steel, was described, with an account of some causative mechanisms. Sensitized and normal sintered steels were tested by electrochemical potentiodynamic reactivation. The test method was evaluated for optimization of microstructure and corrosion properties. Effects of N alloying and liquid phase sintering were also studied. SOME PRACTICAL ASPECTS RELATED TO SINTERED STAINLESS STEELS E. Klar, PK. Samal (SCM Metal Products, North Carolina, USA) It was reported that: hexacyanoferrate can be used to distinguish between austenitic and stainless steel and Fe powders; delubrication in cracked ammonia is superior to air due to less oxidation; and the addition of graphite to 316L stainless steel reduces 0 content to 600 ppm with a resulting three-fold increase in corrosion resistance. CORROSION RESISTANCE OF SINTERED STAINLESS STEELS AND EFFECT OF SULPHOXIDATION M. Ross0 et al (Politechnical University of Torino, Torino, Italy.) It was reported that the treatment of stainless steels in SOz for 1 hour at 500°C resulted in a reduction of porosity and an increase in corrosion resistance in H,S04. Fe,rO, and FeS were detected on the surface. For a 2’%Custeel the rate of dissolution was halved. The weight losses were shown to be in accordance with polarization curves. STRENGTHENING OF AUSTENITIC AND FERRITIC STAINLESS STEEL BY TITANIUM NITRIDE AND NITROGEN AR. Jones et al (AEA Technology, Risley, Warrington, IIK)

Development of stainless steels strengthened by TiN and N was described. The dispersion of TiN was attained by internal nitriding. The steels were reported to have enhanced properties at ambient and elevated temperatures. Potential applications were discussed. EFFECTS OF POROSITY AND OXYGEN CONTENT ON CORROSION RESISTANCE OF STAINLESS STEEL R.M. Larsen et al (Technical University of Denmark, Lyngby, Denmark) The effect of porosity on corrosion resistance of 316L stainless steel was discussed. The corrosion resistance of samples of varying 0 contents and porosity was investigated by salt spray testing. It was reported that corrosion resistance increases with density in the range 6.5 to 7.5 gm.cm-‘r with local corrosion occuring in open pores, Above 7.5 gm.cm ” pores become closed and below 6.5 gm.cm-s pores are very open and there is less localized corrosion. INFLUENCE OF SINTERING TEMPERATURE AND ADDITIONS OF COPPER OR BRONZE ON STAINLESS STEEL F.J. Velasco et al (School of Mines of Rios Rosas, Madrid, Spain) An investigation of the effects of sintering temperature and additions of up to 20X Cu or bronze on corrosion behaviour of 316L and 304L stainless steels was described. Sintering was in vacuum at 1150 or 125O”C, corrosion was assessed in HC1 or H,S04 and microstructures were characterized.

Measurement

and control

QUANTITATIVE NON-DESTRUCTIVE ASSESSMENT OF GREEN DENSITY OF COMPRESSED PRODUCTS .J. Mller et al (Pechiney CRV, Voreppe, France) A rapid non-destructive testing technique for evaluation of green density of pressed parts was described. The method was reported to give accurate results in 20 seconds.

ESTABLISHMENT OF A METHOD FOR ASSESSMENT OF SURFACE ROUGHNESS OF SINTERED PARTS M. Drozda et al (h’ouva Merisinter Sri, Naples, Italy) A statistical analysis of surface roughness parameters was presented. Reproducibility of a single reading, of a whole part and a batch of parts was investigated. It was suggested that a scanning pattern of measurements instead of single meaasuring lines would give more reliable results. ANALYSIS OF MODULUS OF RUPTURE DATAWITHREFERENCE TO STANDARD SPECIFICATIONS A. Wronski et al (University of Bradford,

Bradford, UK) Tests for evaluation of fracture properties, including modulus of rupture, in bend tests were discussed with regard to ANSI/ASTM 8528-76. Analysis of test results was described. Assumptions in analysis were emphasized and differences in data from different tests, three or four point loading tests, were reviewed in relation to specimen defects.

Gradient materials and multi-materials DESIGN AND FABRICATION OF DIAMOND TIPPED TOOLS ON A CERAMIC SHANK R. Watanabe et al (Tohoku Ilniversity, Sendai, Japan) The development and fabrication of a diamond tipped cutting tool on a Sic shank was described. Finite element analysis was used to determine thermal stresses which were reduced by introducing compositionally graded layers between SIC and the diamond tip. PRODUCTION OF DUAL MATERIAL ROTATING PARTS IN NICKEL BASE SUPERALLOYS

A STUDY OF SOURCES OF HARDNESS VARIATION IN MANUFACTURE OF SHOCK ABSORBER PARTS

G. Raisson et al (TECPHY, Imphy, France) The use of HIP to bond a superalloy powder on to a cast alloy base parts was described. Powder densification and diffusion bonding were shown to occur, The bond was characterized by microscopy and mechanical tes1.s and was reported to have adequate strength for the intended application.

I. Acedo Spain)

STRUCTURED SINTERED WEAR RESISTANT COATINGS

An

(Sintermetal

evaluation

of

SA, Barcelona, measurements

of

hardness of sintered automotive shock absorber components was presented. The parts have notches to facilitate lubricant control and the need for hardness uniformity was emphasised. A study of the causes of hardness variations was described and an account of the software for statistical analysis of data was given.

G.F. Archer, D.J. Stephenson (Cranfield JJniversity,Cranfeld, IJK) The use of PM to produce compositionally graded wear resistant coatings was discussed. Applications of such c#oatings in clamshell and conventional extruder barrel linings was described. MPR April 1995

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