This study presents results of stress rupture test of MAR-M-509 cobalt alloy samples, as-cast and after surface refining with a concentrated stream of heat. Tests were conducted on samples of MAR-M-509 alloy castings, obtained using the lost-wax method. Casting structure refining was performed with the GTAW method in argon atmosphere, using the current I = 200 A and electrical arc scanning velocity vs = 100, 150, 200 and 250 mm/min. The effect of rapid resolidification of the MAR-M-509 alloy on the microstructure was examined and significant improvement in stress rupture test was observed.
In this study, different amounts of tantalum carbide (TaC) powders (5, 10 and 15 wt.%) are added to Vanadis 4 Extra steel powders. The composite powders are sintered at 1260, 1280, 1300, 1320, 1340 and 1360°C for 1 h, respectively. The experimental results showed that good mechanical properties (hardness 79.7 HRA, TRS 2246 MPa) were obtained by the addition of 10% TaC sintered at 1320°C for 1 h. Furthermore, the optimal sintered V4ES/TaC (Vanadis 4 Extra steel / TaC) composites after sub-zero treatment possess the highest hardness (80.9 HRA) and transverse rupture strength (TRS) values (2445 MPa), as well as a better polarization resistance (658.99 Ω·cm2). After sub-zero treatment, the VC carbides decompose and re-precipitate refined VC carbides within the grains (VC carbides are formed in steel powder); moreover, the TaC particles are still uniformly distributed around the grain boundaries, which results in dispersion strengthening and precipitation hardening. The results clearly reveal that sub-zero heat treatment effectively improves the microstructure and strengthens the V4ES/TaC composite.
This article asks the question to what extent Ryszard Nycz’s ambitious project of cultural practice outlined in his book Culture as Verb succeeds in opening up ‘a new form of knowledge’ and thus equipping the humanities with a fresh validity. Nycz takes up the poststructuralist concept of the humanities as a site of alternative or subversive knowledge, founded on the principles of interpretation and textual dispersion, and refocuses it on involvement (participation) and binary oppositions (borders), i.e. human vs. nonhuman, or nature vs. culture as a construct. The article, rather than addressing the issues of involvement and borders (liminality), concentrates instead on the contradictions that Nycz’ s theory gives rise to when applied to history, time and the emergence of subjectivity (identity). There is nothing objectionable about the proposition that temporal change is at the very core of culture, yet its locus must be sought not in the proclamations of individual agents, but in the conceptual ruptures that expose and reveal the boundaries of (collective) consciousness and unconsciousness, i.e. the operation of contingency.