Ti Zhou

Optimization of Laser Processing Parameters and Their Effect on Penetration Depth and Surface Roughness of Biomimetic Units on the Surface of 3Cr2W8V Steel

Biomimetic coupling surface is a recent development in surface science of materials. One of the important methods to achieve this surface is to manufacture large numbers of structural units by certain techniques, arranging them regularly on the surface layer of materials to form the biomimetic structure. The penetration depth and the surface roughness of units are two crucial factors that affect strongly the properties of materials. In this paper, a YAG pulsed laser with varied parameters (electrical current 200 A to 300 A, pulse duration 5 ms to 15 ms, frequency 4 Hz to 10 Hz and scanning speed 0.24 mm·s−1 to 0.72 mm·s−1 ) was used to fabricate these units on the surface of 3Cr2W8V die steel. The penetration depth and surface roughness of the units were investigated based on orthogonal experimental design. To maximize the penetration depth and minimize the surface roughness, the range analysis and subsequently overall balance method were adopted to identify the most significant factor and level. Meanwhile the most preferable combination of the laser processing parameters was selected. The effect of laser processing parameters on the penetration depth and surface morphology of units was analyzed. The interrelationship among the processing parameters, the penetration depth and the surface roughness was discussed.

Effects of Different Graphite Types on the Thermal Fatigue Behavior of Bionic Laser-Processed Gray Cast Iron

In order to study the thermal fatigue behavior of bionic gray cast iron with different types of graphite (from A to E), first, the effects of A to E types of graphite on the thermal fatigue properties were studied. At the same time, the crack initiation and propagation modes of different gray cast iron types were analyzed. In addition, for improving the thermal fatigue properties of gray cast iron, the anti-fatigue mechanism of the coupled bionic structure on gray cast iron was investigated. In this case, the thermal fatigue properties were measured by the number, length, and width of cracks. The results revealed that the gray cast iron with A-type graphite had the best fatigue resistance compared to others. However, C-, D-, and E-type graphite exhibited the greatest effect on the number, length, and width of crack. Interestingly, the bionic gray cast iron sample with D-type graphite exhibited improved fatigue resistance most obviously compared to the non-bionic sample.