A Study Of Laser Cladding By Wire On 35CrMo Alloy

Laser cladding is a new surface modification technology, which can be used to prepare high-performance with super properties and bring excellent structure and property. However, too much research strength was focused at cladding by powder but less by wire at present. And it was proved that laser cladding by wire is more brilliant at the stability of cladding technology and the availability of precursor materials.Fiber laser was adopted to prepare 1Cr13 martensite stainless steel on the surface of 35CrMo alloy by wire. Via optical microscope, scanning electronic microscope (SEM) and microhardness testing machine to analyze the microstructure, the distribution of alloying agent and the cross-sectional hardness of the cladding respectively, besides optimized the processing parameter. A fine without macro and micro defect coating was gained, whose microhardness is 2.5 times of the substrate, remarkably improved the surface performance.The results showed that: the main elements content of the layer caused by the convection of the pool hold at a steady area, which nearly matched with the precursor material,; the diffusion effect by the solution gradient leaded a non-uniform zone existed in the bonding area and each element distributed gradually. The microstructure of laser clad coating was consisted of cystiform and columnar crystal predominantly, which was homogeneous and compact, grown in a epitaxial way; the heating effect zone (HAZ) was consisted with coutinuous cooling structure, and the hardness also varied in a gradient way.; And the processing parameter have a large effect on the quality of cladding layer: higher power could elevate the efficiency of laser cladding, the width and height of the cladding layer were improved with the higher scanning speed, the limit scanning speed was 1.0m/min; the feeding speed could range in a great extent when the laser power and scanning speed match well; the optimum process parameter was: laser power P=4.0kw, scanning speed Vs=0.3m/min, feeding speed Vw=5~9m/min.Besides, a overlapping layer with fine formation, little size deviation and none obvious defect was preformed based on optimum process parameter. A second fusion zone and HAZ existed in the former layer, for the latter layer had a second heating on the former that the microstructure and property would change periodically, partly normalizing and partly tempering, the hardness of layer also varied periodically, highest in the normalizing zone while lowest in the tempering zone.