Sinterizazio-atmosferaren eragina M graduko (ASP 30 ... - Euskara
Sinterizazio-atmosferaren eragina M graduko (ASP 30 ... - Euskara Sinterizazio-atmosferaren eragina M graduko (ASP 30 ... - Euskara
Urrutibeaskoa et al . Metallographic changes on sintering M grade steels 309 3 oO o o. E o U C) 3 o U rw Ú V^ C) a L W ú 3 Ú w U o C) N L a o 0 E 7 O O O V Ú Ca) Ú • > > >z >z ro L a N 00 N) 00 V') N O~ h I M N N 00 00 71 ) V) OC M .-~ rn N 7 V r. r V 7 '• t- J C vi N M 7 V t M 0 O cC O O cC O Ce Ú O Ú Ú~ Ú~ • >z > > z' >z ñ. F H z ,) or. r- or M O l N'.O N N .- V V V O Cn N O M M N - - 71r- I'00N~ O V) V [N NV 00 .--''O M-N • ,~ NMOM'il M t- C? 7t O M o0 N 1 ti M M OM U1U UX .) N 71 N - h h N N NT 00 00M 1O N n M M N M ~, M 71 "7 ~, C) 00 O\ O .--+ t \O cn N O) 00 ro U Ú C.) W we~ F 4a • u) • O 00 >U o~ 0 N Ñ H N O o~ v C7 M C L .~ Uca á w . d M Ñ E O a - O a 0 ,0 -0 tn ~ ~ Ñ w • Nv .0 a • 1O O O • a) a .E ú - E • y y CC ? á CO C • L E O O • O U Dó N Ñ .~ Powder Metallurgy 1990 Vol . 33 No . 4 a É Ú C3 CS O E ú N 1 d a) y y L In O II C H C? C~, I:?I 1~1 19 ~C 10 V M M M M 09 71 7 d Cv G) L. Lr 0. ú O E ú ca
310 Urrutibeaskoa et al . Metallographic changes on sintering M grade steels Table 1 M 6C carbide compositions, at .-% Steel grade Mo V Cr Fe CO W W + Mo Fe + Co Sintered in vacuum M3/2 21 .7 6 .9 3 .9 49 .3 . . . 18 .2 39 . 9 49 . 3 Px30 19 .2 6 .4 5 .3 45 .9 5 .7 17 .4 36 .6 51 .6 M2 19 . 0 7 .3 4 .4 50 . 5 18 .8 37 . 8 54 .9 M2, STEM15 1 . 5 4 6 49 39 40 . 5 49 M2' 3 19 7 7 48 19 38 48 M2 23 20 7 6 49 18 38 49 M42 29 .4 4 .7 4 .9 48 .8 5 . 1 7 .1 36 .5 53 .7 M7' 7 19 3 5 70 3 22 70 Sintered in 90N,- 9H 2 M3/2 Px30 M2 1CH4 21 .7 20 .0 20 .2 3 .0 3 .3 2 .8 4 . 1 4 . 6 4 .5 52 .1 47 . 4 51 .4 5 .7 . . . 19 .1 19 . 0 21 .2 40 .8 39 .0 41 .4 52 .1 53 .1 51 . 4 M42 37 .0 1 .6 2 . 9 30 .9 4 .3 23 .4 60 .4 35 .2 element V, which is present in lower quantities in the specimens sintered in the industrial atmosphere) . This is not the case with the MC carbides which are transformed, changing from grey to small black carbonitrides with a higher concentration of V in the specimens sintered in the industrial atmosphere . In this steel, eutectic carbides can also be produced by sintering at temperatures higher than the optimum sintering temperature . Some examples of carbides present in eutectic form in Px30 oversintered both in vacuum and in the industrial atmosphere are shown in Fig . 4 . In the case of type I eutectic carbides, which are observed after sintering both in vacuum and in the industrial atmosphere at the optimum sintering temperature, a higher quantity of Fe and a lower concentration of W and V are found in the industrial atmosphere sintered specimens than in those that are vacuum sintered . Type MC eutectic carbide is observed after oversintering by only 10 K in vacuum . On the other hand, in the case of type M 6C eutectic carbides, which are also observed for both types of sintering - for oversintering by 15 K for vacuum and 30 K for the industrial atmosphere - the carbide chemical compositions are in both cases very similar . In this material a needle type eutectic carbide is observed after vacuum and industrial atmosphere oversintering by 15 and 40 K respectively . M2 steel Figure 5 shows typical SEM micrographs corresponding to specimens of M2+0 . 2%C sintered at the optimum sintering temperature in vacuum and in the industrial atmosphere . On comparing the microstructures corresponding to vacuum and industrial atmosphere sintering, the most noticeable difference is the transformation of the scarce grey MC carbides observed after sintering in vacuum to the black MX carbonitrides, richer in V than the MC, when sintered in the industrial atmosphere . On the other hand, the M 6C carbides are very similar in morphology, size, and chemical composition for specimens sintered both in the industrial atmosphere and in vacuum . Sintering above the optimum sintering temperature results in the presence of carbides with a eutectic morphology, such as those shown in Fig . 6 . Apart from the usual eutectic carbides, which are very similar to those found in Table 2 MC carbide compositions, at .-% Steel grade Mo V Cr Fe Co W W+Mo M2, spherical MC, 4 µm 15 68 4 3 . . . 10 25 M2, elongated MC 15 47 5 26 . . . 8 23 M42, elongated MC 21 43 7 26 2 2 23 Powder Metallurgy 1990 Vol . 33 No . 4 the steels described above, a eutectic carbide rich in Fe and Cr and smaller and finer than the M 6C is also observed in materials sintered in the industrial atmosphere at just above the optimum sintering temperature (Fig . 6b) . M42 steel Figure 7 shows typical micrographs of steel M42 sintered in vacuum and in the industrial atmosphere . The singular feature found in this steel is the presence of M 2C carbides (marked in Fig . 7a) with a rectangular elongated morphology in the specimens sintered in vacuum . Figure 7 also shows a carbide rich in Fe and Cr . MC carbide in vacuum sintered specimens does not appear in the form of isolated particles, but as grain boundary film . The small, black MX carbonitrides are observed in the specimens sintered in the industrial atmosphere and the chemical compositions of the M 6 C carbides are also found to be abnormally high in W . Oversintering also produces different kinds of eutectic carbides in this steel, as shown in Fig . 8 : type I eutectic carbides, in both vacuum and industrial atmosphere, type II eutectic carbides (found only in vacuum oversintered specimens), M6 C type eutectic carbides, and needle type eutectic carbides (which are also found in materials oversintered in the industrial atmosphere) . DISCUSSION Given the differences in chemical composition between the four steels analysed, it is convenient for comparison to transform the composition from weight to atomic percentages . With reference to the carbides, some precautions must be taken in the microanalysis of small particles due to the interference of the matrix . A recent study has shown that small particle size results in too high a quantity of Fe and Co in the particle analysis owing to matrix effects and that a minimum particle size of -4 gm is required to obtain a good analysis .' M6C primary carbides The presence of massive particles (> 4 µm) enabled the chemical composition of the M 6C carbides to be analysed Table 3 MC carbide compositions, at .-% Steel grade Mo V Cr Fe Co W W+Mo M3/2 14 .3 66 . 6 4 .5 5 .5 0 9 .1 23 Px30 14 .3 66 . 5 4 .1 3 .9 0 . 1 11 . 1 25 M2 14 .5 68 . 0 3 .9 3 .2 0 10 . 4 25 M42 20 .7 42 .6 7 .3 25 .7 1 . 7 2 . 1 23
- Page 255 and 256: Estos contenidos se calcularon para
- Page 257 and 258: -mediante la expresión (2 .31)- y
- Page 259 and 260: do la misma dureza y cantidad de au
- Page 261 and 262: En la figura 5 .13 se presentan est
- Page 264 and 265: 5 .1 Taula: Karburoetan sartzen den
- Page 266 and 267: 5.1V Taula : MC karburoen konposake
- Page 268 and 269: 5 .VIII Taula : Karbono baliokideak
- Page 270 and 271: Material Sinterizazio- Atmosfera At
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- Page 275 and 276: Frecuency (%) 100 90 80 70 60 50 40
- Page 277 and 278: 100 80 ó ' 60 .J W H Z 40 w '< 20
- Page 279 and 280: 1 .4 1 0 .8 0 .4 • 1 0 20 Hondar-
- Page 282 and 283: 6 . ONDORIOAK 1 . % 90 N2-% 9 H2-%
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- Page 287 and 288: 7 . SUGERENCIAS 1 . Explorar hasta
- Page 290 and 291: BIBLIOGRAFÍA (1) P. Payson ; "The
- Page 292 and 293: (39) V .P. Martínez, R .H . Palma,
- Page 294 and 295: (77) H . Takigawa, H . Manto, N. Ka
- Page 296: ARGITARAPENAK . PUBLICACIONES .
- Page 299: PUBLICACIONES . Publicaciones gener
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- Page 314 and 315: Figure 1 Microstructure of T42 + 0.
- Page 316 and 317: Figure 3 Microstructure of T15 (1 .
- Page 318 and 319: . . . 4 --s-- r a- 10 im Figure 5 M
- Page 320 and 321: TABLE V Chemical analysis of M 23 C
- Page 324 and 325: AVOIDING GRAIN GROWTH DURING THE SU
- Page 326 and 327: 90 o GT42 80 o e GT42C VT42 * VT42C
- Page 328 and 329: The presence of these MX carbonitri
- Page 332 and 333: Publishing & Editorial The Institut
- Page 334 and 335: INTRODUCTION Work carried out in th
- Page 336 and 337: etter than 5 Pa during the sinterin
- Page 338 and 339: gas atmosphere (see Table IV for qu
- Page 340 and 341: - Needle type : observed only at hi
- Page 342 and 343: -1o- (18) . These values would give
- Page 344 and 345: Chemical composition of primary car
- Page 346 and 347: CONCLUSIONS 1 . Addition of free ca
- Page 348 and 349: Vasco, 1987, Bilbao, España . 13 .
- Page 350 and 351: TABLE I Chemical analysis of as-rec
- Page 352 and 353: TABLE IV Austenite grain size and p
- Page 354 and 355: TABLE VII Chemical composition of C
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