On the Influence of Tribological Properties of AISI 4140 Annealed Steel against Ceramic Counterparts under Dry and Lubricated Conditions and Their Effect on Steel Microstructure

AISI 4140 steel is still one of the most distinguished steels employed in tribological applications because of its low cost, great mechanical properties, and appropriate wear resistance. In this contribution, the tribological performance of AISI 4140 annealed steel against engineering ceramic was analyzed to promote parameters for the application of this steel, especially in systems that are subjected to contact pressures between 490–1240 MPa. Dry and lubricated pin-on-disk experiments were completed at different normal loads. The worn surfaces were analyzed by contact profilometry, optical and scanning electron microscopies, energy dispersive spectroscopy, and microhardness examinations. In dry conditions, a better friction response was found on the steel tested with ZrO2. Friction coefficient and wear rate resulted in reductions up to 60% and 99% compared with those obtained with Al2O3 and Si3N4 counterparts. A strain-hardening phenomenon due to the friction process was observed on the samples tested with ZrO2 and Si3N4, which showed grain refinement and hardness increment on worn surfaces. Therefore, those systems exhibited better wear responses. In lubricated conditions, all counterparts exhibited low friction and wear, but the performance of Al2O3 and Si3N4 was highlighted. The results demonstrate that the performance of AISI 4140 annealed steel under the tested conditions is comparable with that of the same steel with other surface treatments.

Production processes and statistical analysis of ceramic liner-hole parameters for sustainability and improved thermal efficiency of clean biomass stoves

In engineering, ceramic liners are used as heat retention, insulation, and wear-resistant components for industrial and domestic applications. However, due to lack of production standards, particularly under small industrial operations, there is variation in liner-hole diameter and inter-hole spacing of liners used in clean biomass stoves. This study assessed the production processes and analysed ceramic liner-hole diameters and inter-hole spacings for standardisation. Standardising liner-hole parameters is a major process towards sustainability and improved efficiency. Methods employed were − material composition, particle size distribution analysis, study of production processes, and 51 liner-hole diameters and 66 inter-holes spacing were randomly sampled and analysed. The results indicated material composition of clay (70%), sand (23%), and sawdust (7%) of various particle sizes. A flow chart diagram of 7 production processes was created for standardisation. At 95% C.I, liner-hole diameter of Ø20.8 ± 2(0.66) mm and inter-hole spacing of 27.5 ± 2(1.06) mm were determined. Mean liner-hole diameter of Ø21.03 mm resulted in a relatively high thermal efficiency, ηT =37%. For practical applications, liner-hole diameter of Ø21 mm and inter-hole spacing of 30 mm are recommended. Standardising the production processes and the liner-hole parameters will contribute to sustainable production and thermal efficiency improvement.

INFLUENCE OF MACHINING TECHNOLOGIES ON VALUES OF RESIDUAL STRESSES OF OXIDE CUTTING CERAMICS

Currently, the intensive development of engineering ceramic and effort to replace sintered carbides as cutting materials are in progress. With the development of the sintering technology it is now possible to produce compact ceramic cutting samples with very good mechanical properties. The advantage of these materials is their easy accessibility and low purchase price. In this work, the influence of the finishing machine technology on the values of surface residual stresses of cutting ceramic samples Al2O3+TiC were studying. The samples were supplied by Moscow State University of Technology STANKIN. Measurements made in the X-ray diffraction laboratory at the Department of solid state engineering were performed for both the phases. The influence of the parameters of machining to residual stresses was studied and the resulting values were compared with each other.