Wear mechanism map of uncoated HSS tools during drilling die-cast magnesium alloy

A wear mechanism map of uncoated high-speed steel (HSS) tools was constructed under the conditions of dry-drilling die-cast magnesium alloys. Three wear mechanisms appear in the map based on the microanalysis of drilled HSS tools by SEM, including adhesive wear, abrasive wear and diffusion wear. In the map, there exists a minor wear region which is called "safety zone". This wear mechanism map will be a good reference for choosing suitable drilling parameters when drilling die-cast magnesium alloys.

The effect of sliding speed on the wear of steel-tool steel pairs

This study examines the effect of sliding speed and surface temperature on the wear behavior of an unlubricated mild steel-tool steel contact pair using the pin-on-disc test. The operating conditions and contact pair are of interest to the automotive sheet metal stamping industry and the broader metal forming community, where high contact pressures and moderate forming speeds can result in significant frictional heating and thus affect tool life. It will be shown that, while adhesive wear is dominant at the tool steel surface for all sliding speeds examined, the adhesive wear rate is very sensitive to sliding speed during slow speed conditions but relatively insensitive to sliding speed during higher speed conditions. These higher sliding speeds result in high frictional heating, however, the effect of increasing bulk temperature results in a transition from adhesive wear to material removal-dominated mechanisms. It is concluded that there is a distinct difference in the wear response for comparable surface temperature and bulk temperature conditions, at the low to moderate sliding speeds and temperatures examined in this study. The SEM and profilometry analysis show that the technique of increasing sliding speed to replicate bulk temperature conditions (or vice versa), may not result in equivalent wear rates and mechanisms.

Análise e avaliação dos elementos de penetração no solo de equipamentos rodoviários após revestimento

The main objective is to analyze the abrasive wear resistance to the low stress of the elements that make up the organs of road machinery that are exposed directly to contact with abrasives. These samples were analyzed after these elements are coated superficially by the process of welding electrode coated with (SAER) and the manual process of coating type LVOF thermal spraying. As well, is to provide suggestions for a better recovery and return of these elements, which are reducing costs and avoiding downtime in the fronts of service. The samples were made from a substrate of carbon ABNT 1045 tempered steel, following the same specifications and composition of metals and alloys of constituents was followed the standard governing the dimensions of these samples and in accordance with the corresponding size. The results were evaluated by testing the hardness, abrasion resistance to wear by the low stress and the loss of volume involving the microstructure of coatings analyzed

Efeitos da granulometria, do desgaste e do tipo de material abrasivo no lixamento plano de madeiras

Pós-graduação em Engenharia Mecânica - FEG

Análise e avaliação dos elementos de penetração no solo de equipamentos rodoviários após revestimento

The main objective is to analyze the abrasive wear resistance to the low stress of the elements that make up the organs of road machinery that are exposed directly to contact with abrasives. These samples were analyzed after these elements are coated superficially by the process of welding electrode coated with (SAER) and the manual process of coating type LVOF thermal spraying. As well, is to provide suggestions for a better recovery and return of these elements, which are reducing costs and avoiding downtime in the fronts of service. The samples were made from a substrate of carbon ABNT 1045 tempered steel, following the same specifications and composition of metals and alloys of constituents was followed the standard governing the dimensions of these samples and in accordance with the corresponding size. The results were evaluated by testing the hardness, abrasion resistance to wear by the low stress and the loss of volume involving the microstructure of coatings analyzed

Corrosive and abrasive wear in ore grinding

The relative significance of corrosive and abrasive wear in ore grinding is discussed. Laboratory marked ball wear tests were carried out with magnetic taconite and quartzite under different conditions, namely dry, wet and in the presence of an organic liquid. The effect of different modes of aeration and of pyrrhotite addition on the ball wear using mild steel, high carbon low alloy steel and austenitic stainless steel balls was evaluated. Results indicate that abrasive wear plays a significant role in ore grinding in the absence of sulfides, and rheological properties of the ore slurry influenced such wear. The effect of oxygen on corrosive wear becomes increasingly felt in the presence of a sulfide mineral such as pyrrhotite. Wear characteristics of the three types of ball materials under different grinding conditions are illustrated.

Investigations on the influence of graphite filler on dry sliding wear and abrasive wear behaviour of carbon fabric reinforced epoxy composites

In this experimental study, the dry sliding wear and two-body abrasive wear behaviour of graphite filled carbon fabric reinforced epoxy composites were investigated. Carbon fabric reinforced epoxy composite was used as a reference material. Sliding wear experiments were conducted using a pin-on-disc wear tester under dry contact condition. Mass loss was determined as a function of sliding velocity for loads of 25, 50, 75, and 100 N at a constant sliding distance of 6000 m. Two-body abrasive wear experiments were performed under multi-pass condition using silicon carbide (SiC) of 150 and 320 grit abrasive papers. The effects of abrading distance and different loads have been studied. Abrasive wear volume and specific wear rate as a function of applied normal load and abrading distance were also determined. The results show that in dry sliding wear situations, for increased load and sliding velocity, higher wear loss was recorded. The excellent wear characteristics were obtained with carbon-epoxy containing graphite as filler. Especially, 10 wt.% of graphite in carbon-epoxy gave a low wear rate. A graphite surface film formed on the counterface was confirmed to be effective in improving the wear characteristics of graphite filled carbon-epoxy composites. In case of two-body abrasive wear, the wear volume increases with increasing load/abrading distance. Experimental results showed the type of counterface (hardened steel disc and SiC paper) material greatly influences the wear behaviour of the composites. Wear mechanisms of the composites were investigated using scanning electron microscopy. Wear of carbon-epoxy composite was found to be mainly due to a microcracking and fiber fracture mechanisms. It was found that the microcracking mechanism had been caused by progressive surface damage. Further, it was also noticed that carbon-epoxy composite wear is reduced to a greater extent by addition of the graphite filler, in which wear was dominated by microplowing/microcutting mechanisms instead of microcracking.

Nature of corrosive and abrasive wear in ball mill grinding

Laboratory results of marked-ball wear tests are used to discuss the relative significance of corrosive and abrasive wear in wet grinding. The electrochemical mechanism was investigated by correlating the corrosive wear with the corrosion current obtained from polarization curves under abrasion. Slurry rheology governs the manner in which ground slurries coat grinding balls, thereby influencing not only the grinding efficiency but also abrasive wear. The effects of percent solids and a grinding aid are illustrated.

Effect of microstructure and hardness on the grinding abrasive wear resistance of a ball bearing steel

Grinding media wear appears to be non-linear with the time of grinding in a laboratory-scale ball mill. The kinetics of wear can be expressed as a power law of the type w=atb, where the numerical constant a represents wear of a particular microstructure at time t = 1 min and b is the wear exponent which is independent of the particle size prevailing inside a ball mill at any instant of time of grinding. The wear exponent appears to be an indicator of the cutting wear mechanism in dry grinding: a plot of the inverse of the normalised wear exponent (Image ) versusHs (where Hs is the worn surface hardness of the media) yields a curve similar to that of a wear resistance plot obtained in the case of two-body sliding abrasive wear. This method of evaluating the cutting wear resistance of media is demonstrated by employing 15 different microstructures of AISI-SAE 52100 steel balls in dry grinding of quartz in a laboratory-scale ball mill.

Grinding abrasive wear and associated particle size effect

The type of abrasion that the grinding medium experiences inside a ball mill is classified as high stress or grinding abrasion, because the stress levels at the surface of the medium exceed the yield stress of the metal when hard abrasives are crushed. During dry grinding of ores the medium undergoes not only abrasion but also erosion and impact. As all three mechanisms of wear occur simultaneously, it is difficult to follow the individual components of wear. However, it is possible to show that the overall kinetics of wear follows a simple power law of the type w = at(b), where w is the weight loss of the grinding medium for a specified grinding time t and a and b are constants. Experimental data, obtained from dry grinding of quartz for a wide range of times using AISI 52100 steel balls having various microstructures in a laboratory scale batch mill, are fitted to the proposed equation and the wear rate w is calculated from the first derivative of the equation. The mean particle sizes of the quartz charge DBAR corresponding to 50 and 80% retained size are determined by mechanical sieving of the ground product after a grinding time t and thus the relationship between wear rate and particle size of the abrasive is established. It is found that w increases rapidly with DBAR up to some critical size and then increases at a much lower rate.