Two different metal powder mixtures usable for direct metal laser sintering were analysed. Bulk chemical compositions were determined with ion-coupled plasma–atomic emission spectroscopy. ...Morphological, as well as microstructural properties of individual metal particles were determined with a light microscope and high-resolution field-emission scanning electron microscope (SEM). Additionally, SEM/EDS analysis has been performed for microanalyses of powder particles.
The Cr-V ledeburitic steel Vanadis 6 was vacuum austenitised, nitrogen gas quenched and double tempered under various combinations of heat treatment regimes. For selected samples, a subzero period ...was inserted between quenching and tempering. The results obtained infer that: (1) the as quenched microstructure consisted of martensite, retained austenite and undissolved carbides; (2) the subzero processing reduced the amount of the retained austenite and increased the tetragonality of the martensitic lattice; (3) the as quenched hardness of the steel was higher by 2-3 HRC due to subzero processing; (4) the as tempered hardness increased with increasing austenitising temperature, but it decreased slightly during the subzero period; (5) no negative impact of subzero processing on toughness was recorded; (6) the wear resistance increased with subzero period when a 100Cr6 steel was used as a counterpart.
The number of carbide particles stringers at boundaries and subboundaries of martensite per unit of surface decreases with the third root of tempering time at 1073 K. The accelerated creep rate at ...853 K depends on the number of stringers of carbide particles per unit of surface, and below an inflection point, the creep rate increases strongly. Equations relating for creep rate are discussed in terms of experimental creep rate, number of carbide particles stringers and average particles spacing.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
Molybdenum disulphide (MoS
2) might be a useful addition in the production of composite self-lubricating high-speed steel parts, which are used in different anti-wear applications. MoS
2 might also ...has a favourable influence on the synthesis of sintered high-speed steels (HSSs) improving the compressibility of the metal powder mixture during its cold compaction, as well as acting as a sinterability enhancer of powder compacts during their sintering. In view of this, the compressibility and the sinterability of M3/2 and M35 types of HSS powder mixtures with MoS
2 additions were investigated.
In this article, the influence of MoS
2 additions on the densification during cold compaction and vacuum sintering of selected HSSs is presented. It has been established that the MoS
2 promotes a consolidation of HSS powders during automatic die compaction, as well as final densification during sintering. Sintering of HSS-MoS
2 powder mixtures proceeds by the combination of a reactive and supersolidus liquid-phase sintering process. The added MoS
2 reacts with the steel matrix, enhancing densification. Fine dispersion of complex sulfides (Cr, V, Fe)S is formed, which improves the machinability and tribological properties of sintered steel.
Fe
74Si
11B
14Ni
1 soft-magnetic material was prepared as a powder using water atomisation. Using this method, powder particles of less than 45
μm in diameter were obtained after sieving. In the ...as-water-atomised condition the powder particles were observed to be amorphous. Annealing resulted in the formation of a two-phase nanostructured morphology. The structure of the powders was investigated by high-resolution Auger electron spectroscopy (HRAES) and field-emission scanning electron microscopy (FE SEM) with WDS analytical technique.
A successive grinding technique was used to study changes in microstructure generated by fretting of a ball bearing steel, which was also studied by optical and scanning electron microscopy. The ...white phase was precipitation hardened austenite that grew laterally by coalescence of initial areas of a few micrometres. Similar carbide precipitates were found in areas of residual austenite in rapidly solidified water atomized particles of the same steel. (Abstract quotes from original text)
Molybdenum disulphide (MoS
2) is a well-known and widely used solid lubricant. As such, it might also be a useful addition in the production of composite self-lubricating high-speed steel parts which ...are used in different anti-wear applications. MoS
2 might also have a favourable influence on the synthesis of sintered HSS. In view of this, the compressibility and the sinterability of M3/2 and M35 types of HSS powder mixtures with MoS
2 additions were investigated. In this paper, the influence of MoS
2 on the densification during vacuum sintering of selected HSSs is presented. It has been established that the densification of HSS-MoS
2 powder mixture proceeds by a combination of a reactive and super-solidus liquid-phase sintering process. The added MoS
2 reacts with the steel matrix, enhancing densification. Complex sulphides (Cr, V, Fe)S are formed, whilst the Mo enriches the steel matrix and forms complex carbides with other alloying elements.
Contemporary cutting tools used for High Speed Cutting (HSC), made on the basis of micro-grained cemented carbides with multi-layer protective coating, allow for effective machining of hardened and ...tempered steels of hardness over 50HRc. The characteristic wear of such tools is affected by the fact that the cutting speed is no longer the main influential factor on wear; the wear can also be the consequence of the high-speed tool movements in the feed direction. The paper presents some original research into the wear types, as well as the phenomena in the cutting zone and their relationships to the causes and main wear mechanisms (adhesion, abrasion and diffusion) for the tools used in HSC.
