Papers by Keyword: Laser Transformation Hardening

Abstract: The laser quenching of GCr15 steel by wide band scanning technology was researched. Hardness and depths of laser transformation hardening zones of samples were also measured experimentally. Temperature field and residual stress field in the laser hardening process were numerically simulated by ANSYS software. The calculated results are in good agreement with the experimental results. The distribution of residual stress is closely related to the temperature distribution made by laser heating process. Then the distribution of residual stresses of the laser surface hardened layers was analyzed by using the X-ray diffraction (XRD). Compressive stresses were detected on the surface of the harden layer after the laser transformation hardening process, and the residual stress value of the surface of samples increases with the increasing of laser power. But the residual stress value of surface melting zones of samples is small.

Abstract: This study establishes a 3-D finite element model for the numerical simulation of laser transformation hardening on inner wall of pump barrel through a finite element code-SYSWELD. The change of thermal mechanical parameters with temperature is considered. The temperature field, metallurgy transformation and distribution of residual stress are predicted. The effect of scanning velocity on the temperature, martensite fraction and distribution of residual stress are studied. The results show that peak temperature in the hardened zone reaches to 1067.0°C and the maximum heating and cooling rate of hardened zone are 1.24×104°C/s and 3.68×103°C/s. After treatment, martensite can be obtained as a main phase in the hardened zone whose fraction increases with the decrease of scanning velocity. Compressive stress could be acquired in the hardened zone while the peak of tensile stress exists in the HAZ.

Abstract: In this paper, the specimens of GCr15 steel were quenched by laser transformation hardening experiment and then they were tempered at different temperatures. The tempering micromorphology and microstructure of laser surface hardening layer were studied, and the photos of scanning electric microscope(SEM) were used in the fractal analysis. The relationship between the tempered temperatures and the hardness of the hardening layer surface was researched, and the relationship between the hardness of the hardening layer surface and the fractal dimension of the surface hardening layer SEM photos was also researched.

Abstract: Laser transformation hardening was carried out by HL-1500 CO2 laser on 40Cr steel. The macroscopic and properties were analysised by scanning electron microscope, X-ray diffractometer, microhardness meter and potentiostat. The result indicated that, the hardening layer is mainly constitute by Fe-Cr, C0.09Fe1.91, Fe2Si. After laser transformation hardening the hardness enhanced greatly, the maximum of hardness appears in the subsurface, which value is as about four times as that of the substrate, both wear resistance and corrosion resistance are improved. With the increase of the laser incident angle, microstructure’s inhomogeneity becomes larger, properties become decreased.

Abstract: When applying laser transformation hardening (LTH) on a steel part the aim is to harden a localized area, which results in high hardness value for a defined width and depth of the material. To assure the hardened zone and keep the maximum temperature of the surface below the melting point we have used a finite element model (FEM) to compute the solution for heat distributions and the phase transformation of the material during LTH. Modelling results were used to introduce safe operating regions for LTH with different processing conditions. A problem associated with some LTH applications is the necessity to overlap the hardening passes. The temperature distribution of this phenomenon was also modelled using FEM which truly assist in finding optimum overlapping and technological parameters.