Hardness Evaluation of 88Cu-4Pb-4Sn-4Zn Alloy by Mechanical Alloying with Oxidizing Atmosphere

The investigation of new materials that have properties such as resistance to high temperatures, wear resistance, rigidity, and low weight, involves the use of technological processes with more and more advantages. For this purpose, mechanical alloying is a widely used technique, which consist of high-energy impact between balls inside a container, where constant collisions deform and fracture the material, achieving the alloy of the particles in a solid state. This work focuses on the Vickers hardness evaluation of the copper matrix alloy with 4% Pb, 4% Sn and 4% Zn, in an oxidizing atmosphere, sintered at 800 °C and 900 °C, using milling times of 3 hours, 6 hours and 9 hours. The results show that there is a relationship between the hardness obtained, in the two groups of specimens at 800 ° C and 900 ° C, with the grinding time and the sintering temperature, among others used in the process. An average maximum hardness of 53.4 HV was obtained.

High-Temperature Corrosion Behavior of Al-Coated Ni-Base Alloys in Lithium Molten Salt for Electroreduction

The electrolytic reduction of a spent oxide fuel involves the liberation of oxygen in a molten salt LiCl–Li2O electrolyte, which creates a corrosive environment for typical structural materials. In this study, the corrosion behaviors of Al–Y-coated specimens in a Li molten salt kept under an oxidizing atmosphere at 650 °C for 72 and 168 h were investigated. The weight loss fraction of the coated specimen to bare specimen was approximately 60% for 3% Li2O and 54% for 8% Li2O at 72 h, and approximately 38% for 3% Li2O and 30% for 8% Li2O at 168 h. Corrosion was induced in the LiCl–Li2O molten salt by the basic oxide ion O2− via the basic flux mechanism, and the corrosion product was found to be dependent on the activity of the O2− ion. The increase in weight loss may have been caused by the increase in the O2− concentration due to the increase in the Li2O concentration rather than being because of the increased reaction time. The Al–Y coating was found to be beneficial for hot corrosion resistance, which can be useful for handling high-temperature lithium molten salt under an oxidizing atmosphere.

Characteristic Curves of Iridium-Rhodium Sensing Elements in High-Temperature Transducer Applications

In order to increase the capacity and efficiency factor of gas turbines and internal combustion engines while preserving their high reliability, the gas temperature and its distribution need to be measured in combustion chambers. Values of these temperatures can exceed 1800°С in an oxidizing atmosphere. Therefore, designing temperature transducers for measurements in such severe environments, special attention should be paid to the selection of thermometric materials. The requirements of the necessary accuracy and temperature range over 1800°С in an oxidizing atmosphere are fulfilled only by the temperature transducer based on iridium-rhodium alloys. The characteristic curve of such sensing elements is individual and each temperature transducer is to be calibrated. The paper discusses a technique of determining the individual characteristic curve of iridium-rhodium sensing elements of high-temperature transducers. The preparation steps to be taken prior to the calibration and the main stages of determining the characteristic curve are described. The general view of the experimental set for calibrating the sensing elements is presented. Based on the calibration results, the form of approximating polynomial of the individual characteristic curve is proposed.