Authors: S N Aqida M Maurel D Brabazon S Naher M Rosso
Publish Date: 2009/12/15
Volume: 2, Issue: 1, Pages: 761-
Abstract
This paper presents laser surface modification work performed to improve the lifetime of die materials Die material AISI H13 with typical hardness in the range of 42 to 48 HRC offers high wear and corrosion resistance However the cyclic high temperature conditions along with exposure to high viscosity molten metal in semisolid forming cause the die to wear and crack with resultant shortened die lifetime In this study the thermal stability of die material at elevated temperature was investigated through microhardness testing and a metallographic study AISI H13 samples were laser glazed using CO2 continuous wave mode laser with 106 µm wavelength Samples were attached to a specially designed rotating chuck to enable it to be rotated at speeds up to 1500 rpm and allow flat surface glazing to take place The micro hardness was measured for asglazed samples and annealed samples which were held at temperatures ranging from 550oC to 800oC with 50oC intervals The metallographic study conducted examined the formation of three zones at different depths which were the glazed zone the heat affected zone and the substrate As a result of rapid heating and cooling from the laser glazing process a metallic glass layer was developed which exhibited an average microhardness of 900 HV when exposed to 334E+10 W/m2 laser irradiance within a range of 00011 to 00018 s exposure time Crystallization in glazed zone increased as the annealing temperature increased As the annealing temperature reached above approximately 600oC the microhardness decreased to approximately 600 HV equivalent to approx 54 HRC due to local crystallization These findings show potential direct application of glazed dies for nonferrous semisolid forming and the requirement for thermal barrier protection for application at higher temperatures
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