[en] Ongoing research is currently underway to investigate the thorny problem of how damage originates and accumulates as a result of low-cycle fatigue. This communication describes testing conducted on specimens cut from bars of commercial AISI 304 stainless steel tubing subjected to a constant bending moment at room temperature. A specially-designed test apparatus allowed determination of specimen strength at both one and two strain levels, thereby confirming the presence of the loading effect. Lastly, crack concentration and depth were measured and correlated to physical damage evolution. (orig.)

[en] The applicability of ionitriding process to the ASTM A564 Tp 630 steel is studied. The ionitriding treatment is carried out as a phase complementary to and contemporary with the precipitation hardening. Analyses of surface structures and of size and shape variations induced by the treatment are developed with reference to varied operating conditions and component geometries. (author)

[en] Thermoluminescent properties of three samples of synthetic diamond obtained by chemical vapor deposition (CVD) were investigated. The thermoluminescent response of the three samples was observed increasing linearly with radiation exposure over a wide range of doses (from 60 mGy up to 3 Gy). The measurement of their activation energies and frequency factors are reported. First order kinetics was observed in the three cases

[en] The nitridability at low temperatures (723-773 K) of Fe-Mo-C sintered steels has been studied: the possibility to realize hardened surface layers of appropriate characteristics has been examined also to reduce surface microstructure alterations (e.g. decarburization) and size and shape variations which may occur for thermochemical treatments at higher temperatures. In a semi-industrial ion-nitriding plant Fe-Mo 1.5-C 0.3 (with martensitic matrix) and Fe-Mo 1.5-C 0.5 (with bainitic matrix) sintered steels have been ion-nitrided at temperatures included in the range 723/823 K and for treatment times of 4/24 h. As previously noticed, the first sintered steel, if ion-nitrided at 823 K for more than 8 h, presents a surface hardness of about 700 HV but also a sharp hardness fall (down to 450 HV) immediately beyond the compound layer owing to decarburization phenomena. Reducing the treatment temperature (773 K) this effect does not appear: the nitrided layer shows a regular hardness profile, with maximum hardness value of 720 HV and thickness of about 100 μm, and consists essentially of the Fe₄N γ' cubic nitride and Fe_2-3(C,N) ε hexagonal carbonitride. At the same time, the ion-nitriding treatment in the temperature range 723/823 K has been applied to the second sintered steel. In this case, no decarburization has been observed also for treatments at the highest temperature; the hardness profiles show a gradual decrease from 730 HV to the matrix value (350 HV), but the hardness depth results very limited also for treatment times of 24 h. (orig.)

[en] We report on synthesis of diamond films by direct current glow discharge chemical vapour deposition (CVD) prepared at different deposition conditions, for application in high energy physics. The synthesis apparatus is briefly described. Continuous undoped diamond samples have been grown onto Mo substrates with a deposition area up to 1 cm² and an electrical resistivity as high as 10¹³ Ωcm. The deposition parameters are related to the material properties of the diamonds, investigated by optical spectroscopy, electron microscopy and diffraction analysis. Decreasing the linear growth rate results in good quality films with small remnants of graphite-like phases. The high crystalline quality and phase purity of the films are related to very low values of leakage currents. The particle induced conductivity of these samples is also studied and preliminary results on charge collection efficiency are presented. (orig.)