A study on the effect of laser glazing on metal matrix composites fabricated with carbide-boride-nitride reinforcements

Abstract

Metal matrix composites (MMCs), offers high strength, fracture toughness and stiffness than those offered by their polymer counterparts. They can withstand elevated temperature in corrosive environment than polymer composites. Most metals and alloys could be used as matrices and they require reinforcement such as carbides, nitrides and borides etc. materials which need to be stable over a range of temperature and non-reactive too. Titanium, aluminium and magnesium are the popular matrix metals currently in vogue, which are particularly useful for aircraft applications. MMCs used in structural applications are frequently subjected to the corrosive environment, direct normal stresses and shear stresses and this can adversely affect the surface of the MMC may lead to high wear and fracture at the surface, so in order to avoid this we aim to laser glazing on the MMC surface. The effect of laser glazing on metal matrix composites comprised of steel AISI304 as a metal matrix and TiB2-TiN-SiC as a reinforcement prepared through powder metallurgical process are studied. Various process parameters are selected to fabricate the MMCs as three weight percentage of blended ceramic mixtures 20 wt.%, 30 wt.% and 40 wt.% along with three soaking times as 0 min, 30 min and 60 min and three compaction pressures 740 MPa, 960 MPa and 1180 MPa. Laser glazing is performed by the help of high power continuous wavelength laser on sintered MMC samples. The evaluation of COF, specific wear rate, fracture toughness and scratch hardness are carried out with the help of linear reciprocating tribometre and scratch tester. SEM micrograph analysis and XRD analysis is also carried out for physical characterization. By examining the graphs of tribo-mechanical properties of sintered MMCs and laser glazed MMCs, it is observed that the increase in weight percentage of ceramic reinforcement in metal matrix, increase in soaking time and increase in compaction pressure up to an optimum value as 30 wt.% of ceramics content, 30 min. soaking time and 960 MPa compaction pressure the values of COF increases, while decrease in values of specific wear rate and also scratch hardness and fracture toughness values are found to be optimum at the optimum values of process parameters. While improvement in the tribo-mechanical properties are also observed after the laser glazing on the surface of MMCs.