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Properties of spray formed high speed steels
Electrolytic Cu powder and globular Cu-lO%Sn powder are compared with regard to their use in powder injection moulding. A three-component binder and new debinding cycles were used. The Cu-Sn powder had higher possible solids loading, better shape retention and less loss of strength after debinding. PM’99 The following Abstracts are from papers presented at the 1998 Powder Metallurgy World Congress which was held in Granada, Spain, in
Stainless
steels
SURFACE REACTIONS DURING VACUUM SINTERING OF STAINLESS STEEL C.Terrisse et al. (Chalmers University of Technology, Goteborg, Sweden. 1 Sintering of stainless steel was discussed. It was noted that a high 0 content results in poor mechanical properties and that increased sintering temperature makes oxide films less continuous and improves properties. A study of sintering, at a range of temperatures, of 304L and 316L stainless steels, subjected to low temperature reduction before sintering, was described. ULTRAFINE GRAIN REFINEMENT AND MECHANICAL PROPERTIES OF PM 316L STAINLESS STEEL K.Ameyama et al. (Ritsumeikan University, Shiga, Japan.) High strain processing, consisting of mechanical milling, heat treatment and sintering, was shown to confer an ultrafine grain structure on the sintered alloy In the case of 316L stainless steel this was shown to be due to ambient temperature recrystallization and dynamic recovery of the austenitic phase due to excess vacancies and high angle boundaries which are produced during milling. The steel so processed was reported to have very high strength compared with conventionally treated material. COMPACTION OF STAINLESS STEEL RY ROTARY FORGING T.Canta et al. (Technical University of Cluj-Napoca, Cluj-Napoca, Romania.) Difficulties in consolidation of stainless steels, to high density, were noted. An investigation of rotary forging of 316L stainless steel was described. A range of process variables were studied in relation to mechanical and corrosion properties. It is reported that a density over 7.5 g.cmT3 had been reached. EFFECT OF COMPACTION PRESSURE AND POWDER PARTICLE SIZE ON CORROSION OF STAINLESS STEEL
L.P.Barbosa et al. (IPEN-CNEN/SP, Sao Paulo, Brazil. 1 It was reported that 316L filters had been prepared from 44 to 74 pm and 105 to 210 pm powders at compaction pressures of 100,200,300,400 and 500 MPa, and corrosion in 0.5M H,SO, investigated. It was shown that the best corrosion resistance, by means of a weight loss test, was obtained with filters made from the coarse powder pressed at 300 and 400 MPa. The results were discussed with reference to analysis of the solutions after testing. EFFECTS OF ADDITIVES ON SINTERING OF 17-4PH STAINLESS STEELS Y.Palacy, SEroglu. (Tubitak-MAM, Kocaeli, Turkey. ) Effects of TIC and TiB, on sintering of 17-4PH stainless steel at 1250 to 1350°C in H were investigated. The additives were to increase hardness of the alloy. TIC gave poor densification. In order to reduce sintering temperature and to increase densification MO, B, Ni,B and Ni,B were also added. B was effective in both objectives by means of liquid phase sintering.
Thermal
spraying
spray forming
and
PHASE-DOPPLER-ANEMOMETRY FOR ANALYSIS AND CONTROL OF SPRAY FORMING fiir K.Bauckhage. (Inst. Werkstofftechnik, Bremen, Germany.) Measurement and control in the spray forming process was discussed. It was reported that Phase-DopplerAnemometry had been adopted, after modification, to receive on-line data concerning multi-phase flow conditions within the spray chamber. The experimental data was compared with data from process models which led to improvements in process description. The measurements yielded data concerning mass fluxes and local melt particle size distributions. This helps to establish process control. The measuring technique was described and some results were given. WROUGHT MAGNESIUM ALLOYS MADE BY SPRAY FORMING T.Ehert et al. (Inst. fur WerkstoMkunde und Werkstofftechnik, ClausthalZellerfeld, Germany.) Production of Mg alloys, by spray forming, was discussed. It was noted that the amount of deformation possible in Mg alloys is limited by the hexagonal structure. Experimental production of spray formed Mg alloys, using a high energy gas atomizer, was investigated. It was shown that addition of Ca was beneficial to the mechanical properties.
Good mechanical properties, compared with cast/wought Mg materials, was attributed to fine dispersoids found in spray formed extruded alloys. PROPERTIES OF SPRAY FORMED HIGH SPEED STEELS H.Davin, C.Spiegelhauer. (Danish Steelworks Ltd, Fredriksvaerk, Denmark.) Use of the Osprey process for production of large billets was discussed. It was reported that the process had been used to produce billets of T15 high speed steel. The spray formed steel was evaluated and compared with conventionally produced and PM materials.
Post sintering treatments BORIDING OF PM STEELS WITHOUT HALIDES et (Technical H.Danninger al. University, Vienna, Austria.) Pack boriding of PM steels in a mixture of ferro-boron, C, ferro-manganese and Al,O, was investigated. Either sintered steels were treated or the samples were sintered and borided simultaneously. Surface Vickers microhardness of 1110 to 1370 was attained. It was concluded that Mn acted as a boriding enhancer. Microstructures and properties were described. Tensile strengths up to 835 MPa were attained after heat treatment.
CORROSION OF SINTERED 316L STAINLESS STEEL WITH DIBORIDES ADDED B.Becker, J.D.Bolton. (University of Bradford, Bradford, UK.) Corrosion properties of PM stainless steels were discussed with reference to application. It was noted that additions of B and B compounds enhance sinterability and corrosion resistance. Salt spray and electrochemical techniques were used to evaluate the effects of diboride powder additions to 316L stainless steel. Sintered densities of 7.6 to 7.8 g.cm-” were attained. As-sintered the samples compared favourably with the wrought alloy Removal of the dense surface layer, formed during processing and which sealed the surface, exposed sub-surface residual porosity and a boride network, resulting in reduced corrosion resistance.
Superalloys and intermetallic materials HIGH PERFORMANCE STATIC AEROENGINE PARTS G.Raisson et al. (Tecphy, Imphy, France.) Specification requirements of aeroengine parts, dimensions, shape, MPR
May 2000
35
Stainless
steels
SURFACE REACTIONS DURING VACUUM SINTERING OF STAINLESS STEEL C.Terrisse et al. (Chalmers University of Technology, Goteborg, Sweden. 1 Sintering of stainless steel was discussed. It was noted that a high 0 content results in poor mechanical properties and that increased sintering temperature makes oxide films less continuous and improves properties. A study of sintering, at a range of temperatures, of 304L and 316L stainless steels, subjected to low temperature reduction before sintering, was described. ULTRAFINE GRAIN REFINEMENT AND MECHANICAL PROPERTIES OF PM 316L STAINLESS STEEL K.Ameyama et al. (Ritsumeikan University, Shiga, Japan.) High strain processing, consisting of mechanical milling, heat treatment and sintering, was shown to confer an ultrafine grain structure on the sintered alloy In the case of 316L stainless steel this was shown to be due to ambient temperature recrystallization and dynamic recovery of the austenitic phase due to excess vacancies and high angle boundaries which are produced during milling. The steel so processed was reported to have very high strength compared with conventionally treated material. COMPACTION OF STAINLESS STEEL RY ROTARY FORGING T.Canta et al. (Technical University of Cluj-Napoca, Cluj-Napoca, Romania.) Difficulties in consolidation of stainless steels, to high density, were noted. An investigation of rotary forging of 316L stainless steel was described. A range of process variables were studied in relation to mechanical and corrosion properties. It is reported that a density over 7.5 g.cmT3 had been reached. EFFECT OF COMPACTION PRESSURE AND POWDER PARTICLE SIZE ON CORROSION OF STAINLESS STEEL
L.P.Barbosa et al. (IPEN-CNEN/SP, Sao Paulo, Brazil. 1 It was reported that 316L filters had been prepared from 44 to 74 pm and 105 to 210 pm powders at compaction pressures of 100,200,300,400 and 500 MPa, and corrosion in 0.5M H,SO, investigated. It was shown that the best corrosion resistance, by means of a weight loss test, was obtained with filters made from the coarse powder pressed at 300 and 400 MPa. The results were discussed with reference to analysis of the solutions after testing. EFFECTS OF ADDITIVES ON SINTERING OF 17-4PH STAINLESS STEELS Y.Palacy, SEroglu. (Tubitak-MAM, Kocaeli, Turkey. ) Effects of TIC and TiB, on sintering of 17-4PH stainless steel at 1250 to 1350°C in H were investigated. The additives were to increase hardness of the alloy. TIC gave poor densification. In order to reduce sintering temperature and to increase densification MO, B, Ni,B and Ni,B were also added. B was effective in both objectives by means of liquid phase sintering.
Thermal
spraying
spray forming
and
PHASE-DOPPLER-ANEMOMETRY FOR ANALYSIS AND CONTROL OF SPRAY FORMING fiir K.Bauckhage. (Inst. Werkstofftechnik, Bremen, Germany.) Measurement and control in the spray forming process was discussed. It was reported that Phase-DopplerAnemometry had been adopted, after modification, to receive on-line data concerning multi-phase flow conditions within the spray chamber. The experimental data was compared with data from process models which led to improvements in process description. The measurements yielded data concerning mass fluxes and local melt particle size distributions. This helps to establish process control. The measuring technique was described and some results were given. WROUGHT MAGNESIUM ALLOYS MADE BY SPRAY FORMING T.Ehert et al. (Inst. fur WerkstoMkunde und Werkstofftechnik, ClausthalZellerfeld, Germany.) Production of Mg alloys, by spray forming, was discussed. It was noted that the amount of deformation possible in Mg alloys is limited by the hexagonal structure. Experimental production of spray formed Mg alloys, using a high energy gas atomizer, was investigated. It was shown that addition of Ca was beneficial to the mechanical properties.
Good mechanical properties, compared with cast/wought Mg materials, was attributed to fine dispersoids found in spray formed extruded alloys. PROPERTIES OF SPRAY FORMED HIGH SPEED STEELS H.Davin, C.Spiegelhauer. (Danish Steelworks Ltd, Fredriksvaerk, Denmark.) Use of the Osprey process for production of large billets was discussed. It was reported that the process had been used to produce billets of T15 high speed steel. The spray formed steel was evaluated and compared with conventionally produced and PM materials.
Post sintering treatments BORIDING OF PM STEELS WITHOUT HALIDES et (Technical H.Danninger al. University, Vienna, Austria.) Pack boriding of PM steels in a mixture of ferro-boron, C, ferro-manganese and Al,O, was investigated. Either sintered steels were treated or the samples were sintered and borided simultaneously. Surface Vickers microhardness of 1110 to 1370 was attained. It was concluded that Mn acted as a boriding enhancer. Microstructures and properties were described. Tensile strengths up to 835 MPa were attained after heat treatment.
CORROSION OF SINTERED 316L STAINLESS STEEL WITH DIBORIDES ADDED B.Becker, J.D.Bolton. (University of Bradford, Bradford, UK.) Corrosion properties of PM stainless steels were discussed with reference to application. It was noted that additions of B and B compounds enhance sinterability and corrosion resistance. Salt spray and electrochemical techniques were used to evaluate the effects of diboride powder additions to 316L stainless steel. Sintered densities of 7.6 to 7.8 g.cm-” were attained. As-sintered the samples compared favourably with the wrought alloy Removal of the dense surface layer, formed during processing and which sealed the surface, exposed sub-surface residual porosity and a boride network, resulting in reduced corrosion resistance.
Superalloys and intermetallic materials HIGH PERFORMANCE STATIC AEROENGINE PARTS G.Raisson et al. (Tecphy, Imphy, France.) Specification requirements of aeroengine parts, dimensions, shape, MPR
May 2000
35