In order to improve the wear properties of H13 die steel, the thermal fatigue properties of AISI H13 tool steel were investigated at a varied number of cycles for enhancing surface hardness. A CO 2 laser system was used with a 0.09mm focused spot size on the sample surface. The peak power of 1137kW and pulse repetition frequency (PRF) of 2300Hz were the parameters controlled. The Nabertherm model of a thermal fatigue machine used consisted of the cylindrical high temperature furnace with digital control panel, controlled temperature quenching system and pneumatics control sample movement mechanism. The samples were immersed in molten aluminum and quenched in ionized water emulsion at 17 o C temperature within a specific time per cycle. The quenching system was equipped with a thermocouple to control the water temperature. The testing was done on1,750 and 3,500 cycles. The treated samples was characterized for metallographic study and hardness. The metallographic study was conducted using an optical microscope for laser modified layer thickness and grain size and the hardness properties were measured using a Vickers indenter. Erosion occurred from the sample after 3500 cycles. The hardness of the laser treated layer was lowered, after a thermal fatigue test, from 650 HV 0.1 to 510 HV 0.1. These findings are important for designing high wear resistant surfaces through laser surface modification for applications forming semi-solid dies.
This paper presents laser surface modification of AISI 1025 low carbon steel for enhance surface hardness properties. An Nd:YAG laser system with pulse mode was used in order to modify 10mm thick plate surface. Three controlled parameters were laser power, pulse duration and overlap percentage which ranged from 100W to 200W, 0.4 to 1.0ms and 50% to 90% respectively. The treated samples was characterised for metallographic study and hardness. Metallographic study was conducted using optical microscope for laser modified layer thickness and grain size. Hardness properties were measured using Vickers indenter. The result show that hardness of laser treated area increased due to fine grain size produced in the laser modified layer. The overlapping rates increase significantly with decreasing laser scanning speed. These findings are important high wear applications.
This paper presents a laser melting of high thermal conductivity steel (HTCS) dies for surface properties modification due to die failures during operations. Sample were cut from as-received die without any defect or crack. Melting process was conducted using Nd:YAG laser system with pulse mode at 50 W average power. The laser beam was defocused to a spot size of 1 mm on the sample surface. Parameters controlled in this study were peak power of 800 and 1200 W, and pulse repetition frequency of 80 and 90 Hz. Metallographic study and chemical composition analysis were conducted using Hitachi TM3030Plus scanning electron microscope (SEM) and energy dispersive x-ray spectrometer (EDXS). Surface roughness was measured using Mitutoyo SURFTEST SJ-410 stylus profilometer. Hardness properties of the modified layer were characterized by Wilson Hardness tester at 100 N force. The metallographic study showed high porosity at partially melted zone (PMZ) area. From overall findings, laser processing parameter affected hardness properties and surface roughness of modified layer. Where the surface roughness value obtained is between 1.49 and 3.15 μm, while the hardness value is between 550.9 and 610.9 HV0.1. These findings are significant to parameters selection for hot stamping die surface repair and prolong its service.
This paper presents laser surface modification of gray cast iron for enhanced surface hardness properties. A 300 W high power Nd:YAG laser system with pulse mode was used to modify gray cast iron samples surface. Laser processing was conducted using a 33 full factorial design. Three controlled parameters were laser power, pulse duration and overlap percentage. The modified surface was characterised for metallographic study, roughness and hardness. Metallographic study and surface morphology were conducted using optical microscope while hardness properties were measured using Vickers scale. Surface roughness was measured using a 2D stylus profilometer. The results show that hardness of laser modified surface increased due to grain refinement. The overlapping rates increased significantly with decreasing laser scanning speed which affected sample surface integrity. Low surface roughness obtained at the highest scanning speed of 1400 mm/min, and low power of 830 W with pulse repetition frequency of 50 Hz. Process optimization was carried out for maximum surface hardness and laser modified depth, and minimum surface roughness. These findings indicate potential application of cast iron for high wear resistant applications through laser surface modification.
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