Improving the Properties of Gray Cast Iron by Laser Surface Modification

Abstract

Laser surface modification is a widely used technology to improve the properties of functional surfaces. In this study, the properties of gray cast iron are modified by laser surface modification, and the influence of laser quenching on the properties of cast iron in terms of frictional vibration and noise, friction and wear, internal structure, residual stress, hardness, and corrosion resistance is investigated. The experimental results show that, after high-power laser quenching, the frictional vibrations and noise of most gray cast iron specimens are decreased, but the coefficients of friction against a bearing steel counterface are increased and more stable. The surface and sub-surface hardness of all laser-quenched cast iron specimens is significantly increased. The residual stresses on the surface of the cast iron specimens are significantly increased and changed from tensile to compressive residual stresses. Experimental modal testing results show that the modal damping ratios of the laser-treated specimens are increased significantly, although their modal frequencies are not significantly changed. In addition, through the metallographic observation, XRD (X-ray diffraction) analysis, and TEM (transmission electron microscopy) observation, it is found that the microstructures of the cast iron specimen after high-power laser modification become fine-grained, and the pearlite and ferrite in the matrix become fine martensite, which leads to the improvement of the dynamical, tribological, and chemical properties of cast iron after laser modification.

Properties of Laser-Alloyed Stainless Steel Coatings on the Surface of Gray Cast Iron Discs

“…In addition, microstructure observation and phase change analysis of the laser-alloyed coatings were carried out with metallographic observation and XRD (X-ray diffraction) analysis to explore the mechanisms of both vibration and noise reduction and corrosion resistance. The surface-coating fabricating methodology used in this study was significantly different than that in our previous studies [33] and the properties of the laser-alloyed coatings were remarkably improved.…”

“…While in the tribological tests, the friction-induced vibrations and noise were measured using a triaxial accelerometer (Kistler-8766A50M5, Shanghai, China) and a microphone (sound pressure sensor INV9206, BOINV, Beijing, China) using the DASP (data acquisition and signal processing) system developed by Beijing Oriental Institute of Vibration and Noise (BOIVN, Beijing, China). More details of the experimental setup for the tribological and dynamical tests can be found in Sai et al [33].…”

“…The multiple diffraction peak intensities of discs 8, 9, and 11, shown in Figure 10, suggest that some new compounds were developed via laser alloying, and the phase composition changed from a simple compound to complex compounds of C, Si, Ni, Cr and Fe, i.e., the microstructures of the laser-alloyed layer were mainly acicular martensite and ledeburite [33].…”

“…The phase analyses of the original disc 0 and laser-alloyed discs 8, 9, and 11 are shown in Figure 10, from which it can be seen that the phase composition of the original disc 0 is mainly austenite, Fe3Si and [Fe, Ni], while the phase composition of discs 8, 9, and 11 is mainly austenite, martensitic, [Fe, Ni], Fe3Si, and Cr23C6. The multiple diffraction peak intensities of discs 8, 9, and 11, shown in Figure 10, suggest that some new compounds were developed via laser alloying, and the phase composition changed from a simple compound to complex compounds of C, Si, Ni, Cr and Fe, i.e., the microstructures of the laser-alloyed layer were mainly acicular martensite and ledeburite [33].…”

Improvements in Wear and Corrosion Resistance of Ti-W-Alloyed Gray Cast Iron by Tailoring Its Microstructural Properties

“…The surface coating technique has a limitation in terms of being applied in complex geometrical structures, and a long amount of time is required in the process of its mass production [1]. Laser treatment for the surface hardening of GCI has been demonstrated for the improvement in its mechanical properties and wear and corrosion resistance [24][25][26]. But the laser treatment process has the adverse effects of generating a non-homogenous phase transformation in a metal matrix, and this technique can only be applied on a small scale instead of in mass production [27].…”