Solidification Mechanism And Organization Evolution Of Iron-based Alloy Coating By Mechanical Vibration Assisted Laser Cladding

Laser cladding, as one of the important means of material surface modification, and increase material manufacturing technology important branch. Cracking problem is the most important reason to retard the industry employing of laser-cladding techniuque. Many materials scientists have done a lot work for it and got many achievements. iron-based alloy coatings were fabricated on 45 medium carbon steel by the combination of laser cladding and mechanical vibration surface modification process. The research contents will cover the macro-appearance, soildification characteristics, coating cracking, microhardness, Mechanical vibration under the action of laser cladding iron-based alloy coating solidification mechanism and organization evolution were discussed. For iron-based alloy surface preparation without stomatal crack functional composite coating provides a new technical way, and to enlarge the surface modification of laser cladding technology in iron-based alloy structural materials such as performance optimization, and provide theoretical basis for further industrial application.The microstructure, element distribution, phase composition and microhardness of iron-based alloy cladding coatings were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy disperse spectroscopy (EDS) and HVS-1000 hardness tester. To study the mechanical vibration assisted laser cladding iron-based alloy solidification microstructure characteristics of the coating. The microstructure of cladding coating interface transition from plane crystal to banded structure and columnar crystal under mechanical vibration conditions, and the grain refinement effect is the most obvious when the amplitude is 0.13-0.18 mm. The enhanced phase in cladding coating transition from short rod to granular, lamellar and banded structure with the increase of vibration frequency, and the distribution patterns change from random distribution to dispersed and network distribution. There is a synergetic mechanism influence of amplitude and frequency on the microstructure and distribution of the cladding coating.The results show that the cladding coatings are mainly composed of a-(Fe,Cr) solid solution, M7C3(M=Fe,Cr) carbide, Fe2B boride and a small amount of Fe0.9Si0.1 compound. Diffraction peak width after loading mechanical vibration, grain integrity, combined with metallographic figure can be seen that grain refinement, the cladding layer porosity basic disappearance, crack, cracking tendency to reduce. Mechanical vibration on the mechanical effect of laser cladding pool, mechanical vibration on the melt local produce pulsating flow, resulting in a periodic cycle a force ACTS on the secondary dendrite. Role in the secondary dendrite force related to amplitude and frequency, the influence of the amplitude is greater. Only when the amplitude and frequency in harmony, refine the grain size effect is best.In terms of macro-morphology coating surface, Results show that the cladding angle of laser cladding coating is greater when combined with mechanical vibration. Provided with the same laser specific energy and amplitude of vibration, the cladding angle under frequency 200 Hz is larger than the one with frequency 100 Hz, and the cladding angle reaches the minimum value when the amplitude is 0.10 mm. Mechanical vibration assisted cladding layer under the action of the average microhardness is higher than without mechanical vibration cladding layer around 110HV0.2, increased by 13.9%. Amplitude and frequency there is synergy the cladding layer of grain size and increase the influence of the microhardness distribution form and cladding layer.