Bionic Strengthening Process And Property Analysis Of 45 Steel By Laser Quenching

The wear and fracture is the main reason of the part inactivation, and these failure modes often occur in the surface of materials. Therefore, to improve the surface performance of mechanical accessory and prolong its lifespan have theoretical significance and practical value.This paper chose 45 steel which is widely used in industry as the experimental material. Firstly, using the method of orthogonal test, the effects of process parameters (defocusing amount、current、scanning speed) on the surface hardness of the material were studied and the optimal process parameters were obtained. Secondly, based on bionics research, some bionic reinforcement models were designed which were inspired by blade, ground beetle shard, dragonfly wings, shell and lizards scutella. Then these bionic reinforcement models were applied in the surface of 45 steel by laser quenching. Last, through the wear test and tensile test, we discussed the influence of bionics shape on the laser bionic reinforcement effects as well as the mechanism behind them. The results show that:1. After the treatment, laser affected area with certain morphology makes up the units. Microstructures of the units are significantly refined than the substrate. The structure of the units are consists of completely hardened layer, heat affected zone and base metal. The metallographic structure of completely hardened layer is acicular martensite and austenite, the depth and width of it is 0.48mm and 1.15mm, respectively, the microhardness of it is 842 HV that is 18% higher than integral quenching. The metallographic structure of the heat affected zone gradually transformed into pearlite and ferrite from martensite, the thickness of it is 0.1-0.2mm, the microhardness of it gradually reduce to 438HV from 823HV.2. The wear rate of laser bionic reinforcement samples, substrate and gridding sample are 1.70×10-5 mm3/(m·N)、1.33×10-5mm3/(m·N)、9.34×10-6 mm3/(m-N)、2.38×10-5 mm3/(m·N)、1.54×10-5 mm3/(m·N), respectively. Compared with the substrate, the laser bionic reinforcement samples and the gridding sample is improved. From the comparison of the overlapping sample and the laser bionic reinforcement samples, the wear resistance of overlapping sample is superior to the spot sample and inferior than the striation sample and the gridding sample. From the comparison of the laser bionic reinforcement samples, the wear resistance of the gridding sample is the best.3. The laser bionic reinforcement processing can improve the strength of 45 steel. Compared with the substrate, tensile strength and yield strength of the striation sample increased by 10.8% and 24.1% respectively; tensile strength and yield strength of the gridding sample increased by 3.3% and 16.7% respectively; tensile strength and yield strength of the spot sample increased by 2.3% and 12.2% respectively. Strengthening effect of the laser bionic reinforcement processing is attributed to the microstructure changes in the units and the stress transition from the substrate to the units. Because of the stress transfer in the laser bionic reinforcement samples, the units would carry higher tensile stress, and thus stress distributed in the substrate is much lower than that in the untreated samples with the same external loading. Therefore, higher external tensile load will be applied when the substrate of the striation sample reaches its yield point and failure point.