The Research Of In-Situ Synthesis Net-Structure Carbide Reinforce Fe-Based Surface Composites

The network structure is a new type of composite material as a enhance form. That is, theenhancing phase and matrix form own and each other through a continuousthree-dimensional network structure in space. The existing studies have shown that thestrengthening effect is better than the traditional particle-reinforced, whisker/shortfiber-reinforced and long fiber-reinforced and other forms. At present, little study of thenet-structure to enhance the Fe-based composites has been done.This issue in-situ separating out wolfram carbide and chromium carbide compositecoating with different coating compositions are fabricated on the common45steel surfaceby laser cladding with optimal laser parameters. Microanalysis on the coating is carried outavailable by material modem analysis methods. Results show that coating melting zonemorphology and the crystal size are evolving in a certain rule with the change of coatingcomposition. Composite coating is mainly composed of γ-(Ni, Fe) and a great deal of in-sitsynthesized stable phases of WC, Cr3C2, and meta-stable phases. They exist in the coatingsmelting zone with the state of the advanced eutectic metal matrix in the dendrites andeutectic mixture in inter granular. High density dislocation pile-up lies in the interface ofthe matrix and the second phase, which induce the sub-structure fining of the metal matrix.The output of the in-situ product varies with the content of the coating composition.Analysis on the mechanical properties of the coating show that the coatings microhardness increases prominently comparing with the substrate, which presents gradientdistribution with stable transition from the surface to substrate and is little influenced bythe coating composition for the good cladding quality specimen. The main strengtheningmechanisms of the coating are fine grain strengthening, hardy particles dispersingstrengthening, super saturation solid solution strengthening and dislocation pile-upstrengthening. Microstructure of the coating is prominently refined compared with thesubstrate. The grain refinement behaviors related to the thermal and quality conduction, the increasing of the inhomogeneous nucleation induced by the in-situ synthesized hardyparticles and the substructure refinement caused by the strong movement of the dislocationin the bonding metal matrix. The materials abrasive resistance increases prominently afterlaser cladding and the main abrasive mechanisms in the coating are Micro-grinding andMicro-tearing.The high temperature oxidation behavior of the coating has been studied incontinuous changing temperature conditions. Results show that high temperature oxidationresistance is fine and uniform and distributed densely.