RESUMO
The present work investigates the friction reduction capability of two types of micro-textures (grooves and dimples) created on steel surfaces using a vertical milling machine. The wear studies were conducted using a pin-on-disc tribometer, with the results indicating a better friction reduction capacity in the case of the dimple texture as compared to the grooved texture. The microscopic images of the pin surface revealed deep furrows and significant damage on the pin surfaces of the groove-textured disc. An optimization of the textured surfaces was performed using an artificial neural network (ANN) model, predicting the influence of the surface texture as a function of the load, depth of cut and distance between the micro-textures.
RESUMO
The life of metal forming dies and the efficiency of tooling industries depends on the mechanical and wear properties of tool steel. These properties can be further improved by depositing the ceramic coating on heat-treated tool steel. Numerous coating materials with various excellent features are already available commercially; however, the selection of the best coating material is still an immense challenge for users. Compared to various studies related to material selection problems in the contrasting area of utilization, remarkably, little research work has been done in tooling industries. In the present work, we have identified eight coating materials (alternatives) and nine evaluation criteria under the consultation of an expert in the tooling application and tribological field. To deal with this coating material selection problem, an integrated fuzzy-multi attributed decision-making method is proposed which comprises best worst method and fuzzy-Measurement Alternatives and Ranking according to the Compromise Solution method. This integrated fuzzy- multi attributed decision-making method is used to evaluate the alternatives, and the obtained results were scrutinized via utilizing various sensitivity analysis procedures. In the first phase of analysis, seven scenarios of criteria weight change were used, which was derived by the best-worst method; dynamic matrices are used in the second phase of analysis. In the third and fourth phases, obtained ranks were compared with those obtained by different weight calculation methods and ranking methods, respectively. In the present study, AlCrN/TiAlN coating (alternative Cm5) was found to be the best coating material based on the results obtained after sensitivity analysis. Further, in this study, we have proposed a novel method that helps to solve the coating material selection problem or any kind of selection complications.
RESUMO
Cardan joints are used in transmissions between misaligned shafts, as in all-wheel-drive (AWD) cars and railway applications. Their functioning is accompanied by heavy cyclical loads, with the cardan cross spindles subjected to intensive abrasive wear and pitting. In this paper, a solution to the mentioned issue is proposed, thin anti-wear coatings of Metco 32 and Metco 72 metallic powders deposited by atmospheric plasma spray (APS) on cylindrical samples cut from spindles of two cardan crosses made of 40Cr10 and RUL2 steel. The morphological analysis of the coated surfaces was realized by scanning electron microscopy (SEM), and the elemental composition of the tested samples was elaborated by energy-dispersive X-ray spectroscopy (EDS). To investigate the wear resistance of the coated samples in dry and grease-lubricated conditions, tests at constant load and constant speed were carried out using an AMSLER tribometer. The results of greased tests proved that the expulsion of the lubricant from the tribological contact occurred no matter the combination of coated or uncoated samples. During grease-lubricated tests of ten minutes, the least coefficient of friction was measured for uncoated specimens with better surface finishing; but in dry friction tests, the lowest values of the mean friction coefficients were obtained for the Metco 72 coatings. The porous coatings may act as lubricant reservoirs in long-lasting tests, providing a solution to the expulsion phenomenon of the lubricant to the boundary outside the area of the larger-diameter roller.
