7 research outputs found
Effect of mechanical alloying and annealing on the sintering behaviour of AstaloyCrL powders with SiC and carbon addition
Aktywowane spiekanie proszk贸w austenitycznej stali nierdzewnej AISI 316l poprzez dodatek mikroproszk贸w zaprawy zawieraj膮cej bor
It is well known that boron is widely used in order to enhance sintering process for obtaining high density of sintered iron alloys. It was found that even a small amount of elemental boron added to iron based powder compacts, produces significant increase in densification rate upon formation of a liquid phase. Due to the attractive characteristic the use of boron has also been actively investigated for enhancing sintering stainless steels powders. In present research boron was added as a part of master alloy, which has been designed to provide the formation of wetting liquid phase, with accomplished characteristics for manufacturing controlled densification of sintered austenitic stainless steels powders AISI 316L. In this paper the influence of sintering atmosphere and the boron in 0,1; 0,2; 0,3 and 0,4 wt. % amount on the density, microstructure and selected properties of sintered austenitic stainless steels were reported. Green compacts obtained by cold compaction at 600 MPa reached densities around 6,2 g/cm3. The sintering process was carried out both in pure dry hydrogen atmosphere and in vacuum at temperature 1240 degree Celsius using dilatometer Netzsch DIL 402C. In order to interpret the influence of sintering atmosphere and boron content on the sintering behaviour of boron alloyed austenitic stainless steels powders during heating and isothermal holding, the evolution of the dilatometric curves have been discussed. The as-sintered microstructures were characterized under the SEM (EDS), while the pore morphology by the image analysis. In conclusion it could be affirmed that the addition of the master alloy containing boron to austenitic stainless steels powders, produces a permanent liquid phase that enhances densification compacts during sintering, in particular in hydrogen atmosphere. For this reason the results are promising from a technological point of view, because boron addition could extend applications of sintered stainless steel both with respect to lower sintering temperature and shorter time necessary to obtain well rounded pores which are desirable with respect to mechanical properties and corrosion resistance.Bor jest skutecznym aktywatorem procesu spiekania proszk贸w 偶elaza i proszk贸w stopowych. stwierdzono, 偶e nawet niewielki dodatek boru aktywuje proces spiekania w wyniku pojawienia si臋 cieczy zwil偶aj膮cej powierzchni臋 cz膮stek proszk贸w, przyczyniaj膮c si臋 do wzrostu stopnia zag臋szczenia spieku. Dzi臋ki interesuj膮cym charakterystykom bor stosowany jest r贸wnie偶 do aktywowania spiekania proszk贸w stali nierdzewnych. Celem przeprowadzonych bada艅 by艂o wyja艣nienie wp艂ywu dodatku boru w ilo艣ci 0,1; 0,2; 0,3 i 0,4% cie偶. wprowadzonego do mieszanki proszk贸w w postaci mikroproszk贸w zaprawy zawieraj膮cej bor, na kszta艂towanie sie mikrostruktury i w艂a艣ciwo艣ci spiekanych austenitycznych stali nierdzewnych AISI 316l. wypraski prasowano pod ci艣nieniem 600 MPa uzyskuj膮c g臋sto艣膰 6,2 g/cm3. spiekanie przeprowadzono w atmosferze suchego wodoru oraz w pr贸偶ni, w temperaturze 1240 stopni Celsjusza, wykorzystuj膮c dylatometr Netzsch DIL 402c. w oparciu o przebieg krzywych dylatometrycznych analizowano wp艂yw dodatku boru oraz rodzaj zastosowanej atmosfery na przebieg procesu spiekania. Ponadto analiz臋 mikrostruktury przeprowadzono w oparciu o obserwacje SEM (EDS), a morfologi臋 porowato艣ci w oparciu o analiz臋 obrazu. Stwierdzono, 偶e dodatek boru w postaci mikroproszk贸w zaprawy przyczynia sie do aktywacji procesu spiekania w szczeg贸lno艣ci w atmosferze wodoru. Uzyskane wyniki s膮 bardzo interesuj膮ce nie tylko z naukowego punktu widzenia ale r贸wnie偶 z praktycznego, poniewa偶 mog膮 przyczyni膰 sie do zwi臋kszenia zastosowa艅 spiekanych austenitycznych stali nierdzewnych
Odporno艣膰 korozyjna w 艣rodowisku 0.5m roztworu wodnego NaCl spiek贸w austenitycznej stali nierdzewnej 316L modyfikowanych borem
Present study describes results of research conducted on sinters manufactured from a powdered AISI 316L austenitic stainless steel modified with an addition of boron-rich master alloy. The main aim was to study impact of the master alloy addition on a corrosion resistance of sinters in 0.5M water solution of NaCl. In order to achieve it, a potentiodynamic method was used. Corrosion tests results were also supplemented with a microstructures of near-surface areas. Scanning electron microscope pictures of a corroded surfaces previously exposed to the corrosive environment were taken and compared. It was successful to increase the corrosion resistance of AISI 316L sinters modified with master alloy. It was also successful in particular samples to obtain a densified superficial layer not only on the sinters sintered in the hydrogen but also on sinters sintered in the vacuum. No linear correlation between presence of the densified superficial layer and the enhanced corrosion resistance was noticed.W poni偶szym artykule zaprezentowano wyniki bada艅, jakie zosta艂y przeprowadzone na spiekach wykonanych z proszku austenitycznej stali nierdzewnej AISI 316L z dodatkiem mikroproszku bogatej w bor zaprawy. G艂贸wnym celem by艂o poznanie wp艂ywu, jaki ma dodatek zaprawy na odporno艣膰 korozyjn膮 badanych spiek贸w w 艣rodowisku 0.5M roztworu wodnego NaCl. W tym celu u偶yto metody potencjo- dynamicznej. Wyniki bada艅 korozyjnych zosta艂y uzupe艂nione o mikrostruktury strefy przypowierzchniowej. Wykonano r贸wnie偶 zdj臋cia powierzchni poddanych testom korozyjnym przy u偶yciu metody SEM. Powodzeniem zako艅czy艂y si臋 pr贸by podwy偶szenia odporno艣ci korozyjnej spiek贸w AISI 316L poprzez wprowadzenie bogatej w bor zaprawy zar贸wno dla spiek贸w spieczonych w atmosferze wodoru, jak i tych spieczonych w pr贸偶ni. W wybranych spiekach uzyskana zosta艂a zag臋szczona warstwa przypowierzchniowa nie tylko na spiekach spiekanych w atmosferze wodoru, ale r贸wnie偶 na spiekach spiekanych w pr贸偶ni
Corrosion Behaviour Of Sintered AISI 316L Stainless Steel Modified With Boron-Rich Master Alloy In 0.5M NaCl Water Solution
Present study describes results of research conducted on sinters manufactured from a powdered AISI 316L austenitic stainless steel modified with an addition of boron-rich master alloy. The main aim was to study impact of the master alloy addition on a corrosion resistance of sinters in 0.5M water solution of NaCl. In order to achieve it, a potentiodynamic method was used. Corrosion tests results were also supplemented with a microstructures of near-surface areas. Scanning electron microscope pictures of a corroded surfaces previously exposed to the corrosive environment were taken and compared. It was successful to increase the corrosion resistance of AISI 316L sinters modified with master alloy. It was also successful in particular samples to obtain a densified superficial layer not only on the sinters sintered in the hydrogen but also on sinters sintered in the vacuum. No linear correlation between presence of the densified superficial layer and the enhanced corrosion resistance was noticed
Analysis of the oxidation process of powders and sinters of the austenitic stainless steel
Enhanced densification of PM steels by liquid phase sintering with boron-containing master alloy
Reaching high density in PM steels is important for high-performance applications. In this study, liquid phase sintering of PM steels by adding gas-atomized Ni-Mn-B master alloy was investigated for enhancing the density levels of Fe- and Mo- prealloyed steel powder compacts. The results indicated that liquid formation occurs in two stages, beginning with the master alloy melting (LP-1) below and eutectic phase formation (LP-2) above 1373 K (1100 脗掳C). Mo and C addition revealed a significant influence on the LP-2 temperatures and hence on the final densification behavior and mechanical properties. Microstructural embrittlement occurs with the formation of continuous boride networks along the grain boundaries, and its severity increases with carbon addition, especially for 2.5 wt pct of master alloy content. Sintering behavior, along with liquid generation, microstructural characteristics, and mechanical testing revealed that the reduced master alloy content from 2.5 to 1.5 wt pct (reaching overall boron content from 0.2 to 0.12 wt pct) was necessary for obtaining good ductility with better mechanical properties. Sintering with Ni-Mn-B master alloy enables the sintering activation by liquid phase formation in two stages to attain high density in PM steels suitable for high-performance applications. 脗漏 2017 The Author(s