Studies were carried out to determine the effect of heat treatment parameters on the plastic properties of unalloyed ausferritic ductile iron,
such as the elongation and toughness at ambient temperature and at – 60 °C. The effect of austenitizing temperature (850, 900 and 950°C)
and ausferritizing time (5 - 180 min.) at a temperature of 360°C was also discussed. The next step covered investigations of
a relationship that is believed to exist between the temperature (270, 300, 330, 360 and 390 °C) and time (5, 10, 30, 60, 90, 120, 150, 180,
240 min.) of the austempering treatment and the mechanical properties of unalloyed ausferritic ductile iron, when the austenitizing
temperature is 950°C. The “process window” was calculated for the ADI characterized by high toughness corresponding to the EN-GJS800-10-RT
and EN-GJS-900-8 grades according to EN-PN 1564 and to other high-strength grades included in this standard. Low-alloyed
cast iron with the nodular graphite is an excellent starting material for the technological design of all the ausferritic ductile iron grades
included in the PN-EN-1624 standard. The examined cast iron is characterized by high mechanical properties stable within the entire range
of heat treatment parameters.
Weld metal deposit (WMD) was carried out for standard MMA welding process. This welding method is still promising mainly due to the high amount of AF (acicular ferrite) and low amount of MAC (self-tempered martensite, retained austenite, carbide) phases in WMD. That structure corresponds with good impact toughness of welds at low temperature. Separate effect of these elements on the mechanical properties of welds is well known, but the combined effect of these alloy additions has not been analyzed so far. It was decided to check the total influence of nickel with a content between 1% to 3% and molybdenum with content from 0.1% up to 0.5%.
The authors studied the fracture mechanical properties under half-symmetric loading in this paper. The stress distribution around the crack tip and the stress intensity factor of three kinds of notched specimens under half symmetric loading were compared. The maximum tensile stress σmax of double notch specimens was much greater than that of single notch specimens and the maximum shear stress τmax was almost equal, which means that the single notch specimens were more prone to Mode II fractures. The intensity factors KII of central notch specimens were very small compared with other specimens and they induced Mode I fractures. For both double notch and single notch specimens, KII was kept at a constant level and did not change with the change of a/h, and KII was much larger than KI. KII has the potential to reach its fracture toughness KIIC before KI and Mode II fractures occurred. Rock-like materials were introduced to produce single notch specimens. Test results show that the crack had been initiated at the crack tip and propagated along the original notch face, and a Mode II fracture occurred. There was no relationship between the peak load and the original notch length. The average value of KIIC was about 0.602 MPa×m1/2, and KIIC was about 3.8 times KIC. The half symmetric loading test of single notch specimens was one of the most effective methods to obtain a true Mode II fracture and determine Mode fracture toughness.
The present work, presented the study of effect of different inoculants on impact toughness in High Chromium Cast Iron. The molds were
pouring in industrial conditions and samples were tested in laboratory in Faculty of Foundry Engineering at AGH. Seven samples were tested
- one reference sample, three with different addition of Fe-Ti, and three with different addition of Al. The samples were subjected to impact
toughness on Charpy hammer and the hardness test. The presented investigations indicate that for the each inoculant there is an optimal
addition at which the sample obtained the highest value of impact toughness. For the Fe-Ti it is 0.66% and for Al is 0.17%. Of all the
examined inoculants best results were obtained at a dose of 0.66% Fe-Ti. Titanium is a well-known as a good modifier but very interesting
results gives the aluminum. Comparing the results obtained for the Fe-Ti and Al can be seen that in the case of aluminum hardness is more
stable. The hardness of all samples is around 40-45 HRC, which is not high for this type of cast iron. Therefore, in future studies it is
planned to carry out the heat treatment procedure that may improves hardness.
The material selected for this investigation was low alloy steel weld metal deposit (WMD) after MAG welding with micro-jet cooling. The
present investigation was aimed as the following tasks: analyze impact toughness of WMD in terms of micro-jet cooling parameters. Weld
metal deposit (WMD) was first time carried out for MAG welding with micro-jet cooling of compressed air and gas mixture of argon and
air. Until that moment only argon, helium and nitrogen and its gas mixture were tested for micro-jet cooling
Wider application of silicon carbide (SiC) is anticipated for increasing the durability of various structural facilities. For this study, SiC was fabricated with decreased electrical resistivity for precision electrical discharge machining. Two-step reaction sintering by infiltration of molten Fe-Si alloy was applied for SiC fabrication. The procedure included first sintering at 973 K in Ar gas atmosphere and second sintering by spontaneous infiltration of molten Fe-75%Si alloy at 1693 K in vacuum. The sintered structure porosity became very low, forming 3C-type SiC. Results confirmed that molten Fe-75%Si alloy infiltration occurred because of reaction sintering. The electrical resistivity of the sintered SiC infiltrated by molten Fe-75%Si alloy can be improved to be two orders of magnitude lower than that by molten Si, consequently maintaining the high performance of SiC.
New graphite tools were designed and produced to fabricate a semi-finished product from which nine cutting inserts were obtained in one spark plasma sintering process. As a result, WC-5Co cemented carbides were spark plasma sintered and the effect of various sintering parameters such as compacting pressure, heating rate and holding time on the main mechanical properties were investigated. It was shown that WC-5Co cemented carbides spark plasma sintered at 1200°C, 80 MPa, 400°C/min, for 5 min are characterized by the best relation of hardness (1861 ±10 HV30) and fracture toughness (9.30 MPa·m1/2). The microstructure of these materials besides the WC ceramic phase and Co binder phase consists of a synthesized Co3W3C complex phase. Comparison with a commercial WC-6Co cutting insert fabricated by conventional powder metallurgy techniques shows that spark plasma sintering is a very effective technique to produce materials characterized by improved mechanical properties.
The ductility of High Performance Concrete (HPC) can develop both in tension and compression.This aspect is evidenced in the present paper by measuring the mechanical response of normalvibrated concrete (NC), self-compacting concrete (SC) and some HPCs cylindrical specimensunder uniaxial and triaxial compression. The post-peak behaviour of these specimens is definedby a non-dimensional function that relates the inelastic displacement and the relative stress duringsoftening. Both for NC and SC, the increase of the fracture toughness with the confinement stressis observed. Conversely, all the tested HPCs, even in absence of confinement, show practically thesame ductility measured in normal and self-compacting concretes with a confining pressure. Thus,the presence of HPC in compressed columns is itself sufficient to create a sort of active distributedconfinement.
The paper deals with the properties and microstructure of Reactive Powder Concrete (RPC), which was developed at Cracow University of Technology. The influence of three different curing conditions: water (W), steam (S) and autoclave (A) and also steel fibres content on selected properties of RPC was analyzed. The composite characterized by w/s ratio equal to 0.20 and silica fume to cement ratio 20%, depending on curing conditions and fibres content, obtained compressive strength was in the range from 200 to 315 MPa, while modulus of elasticity determined during compression was about 50 GPa. During three-point bending test load-deflection curves were registered. Base on aforementioned measurements following parameters were calculated: flexural strength, stress at limit of proportionality (LOP), stress at modulus of rapture (MOR), work of fracture (WF), and toughness indices I₅, I₁₀ and I₂₀. Both amount of steel fibres and curing conditions influence the deflection of RPC during bending.