Effects of Thermal Fatigue on Laser Modified H13 Die Steel

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 CO2 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 17oC 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 HV0.1 to 510 HV0.1.These findings are important for designing high wear resistant surfaces through laser surface modification for applications forming semi-solid dies

The origin of emission in strontium magnesium pyrophosphate doped with Dy2O3

This paper reports on the luminescence properties of Dy3+-doped 30SrO–30MgO–40P2O5, which had been prepared by solid state reaction. The crystalline phases were identified using X-ray diffraction (XRD) and their luminescence properties were studied using excitation and emission spectra obtained from photoluminescence spectroscopy. The results of XRD patterns indicate that the prepared sample contain crystalline phase of MgP2O6 and SrMgP2O7. The excitation spectrum of 30SrO–30MgO–40P2O5:Dy3+ consists of broad bands’ centre at ~280, 310 and 400–600 nm associated with defects and vacancies of host material. The other feature of sharp peaks is very similar and belongs to Dy3+ ions. The f–f transitions in the range of 417–475 nm correspond to the transitions from 6H15/2 to 4K17/2 + 4M19/2,21/2 + 4I13/2 + 4F7/2, 4G11/2, 4I15/2 and 4F9/2, in the range of 392 nm to 6P3/2 + 6P5/2, and in the range of 312–370 nm to 4K15/2, 6P7/2 + 4M15/2 and 4I11/2, respectively. The peaks at 482, 465, and 455 nm could be assigned to the transition of 4F9/2 → 6H15/2, 4I15/2 → 6H15/2 and 4G11/2 → 6H15/2 of Dy3+, respectively. Dy3+ has emissions due to the atomic energy levels of itself and emissions due to the acceptor levels of defect sites formed by Dy3+

Effects of Thermal Fatigue on Laser Modified H13 Die Steel

In order to improve wear properties of H13 die steel, Thermal fatigue properties of AISI H13 tool steel were investigated at varied number of cycles for enhance surface hardness. A CO2 laser system was used with 0.09 mm focused spot size on the sample surface. The parameter controlled were peak power of 1137 kW and pulse repetition frequency (PRF) of 2300 Hz. Nabertherm model of thermal fatigue machine used consist the cylindrical high temperature furnace with digital control panel, controlled temperature quenching system and pneumatics control sample movement mechanism. The samples were immerge into molten aluminium and quenched in ionized water emulsion at 17oC temperature within specific time per cycle. The quenching system equipped with thermocouple to control the water temperature. The testing was done at 1,750 and 3,500 number of cycles. 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 while hardness properties were measured using Vickers indenter. These findings are important to design high wear resistant surface through laser surface modification for semi solid forming dies application

Labisia Pumila Extract Down-Regulates Hydroxysteroid (11-beta) Dehydrogenase 1 Expression and Corticosterone Levels in Ovariectomized Rats

We evaluated the effects of a standardized Labisia pumila var. alata (LPva) extract on body weight change, hydroxysteroid (11-beta) dehydrogenase 1 (HSD1 1B1) expressions and corticosterone (CORT) level in ovariectomized (OVX) rats. The decoction of LPva has been used for generations among Malay women in Malaysia to maintain a healthy reproductive system.Thirty-six Sprague–Dawley OVX rats were treated orally with LPva extract (10, 20 or 50 mg/kg/day) or estrogen replacement (ERT) for 30 days. Sham operated rats were used as controls. Compared to untreated OVX rats, LPva-treated rats showed less weight gain and had significantly down-regulated HSD11B1 mRNA in liver tissues. HSD11B1 mRNA in adipose tissues increased by 55% (p\0.05) in OVX rats but normalized in rats treated with LPva. Similarly, there was significant down-regulation (p\0.05) of protein levels of HSD11B1 in both liver and adipose tissue of LPva and ERT groups, and CORT levels were significantly reduced in both groups of rats. This is the first study ever conducted to evaluate the beneficial effects of LPva in relation to weight gain caused by estrogen insufficiency. Results implied that the bioactive components in LPva extract affect not only HSD11B1 expressions in both adipose and liver tissues but also decrease circulating CORT. The extract should be explored for its potential use as a natural remedy for weight management