Research On Laser Cladding Fe-based Coating Reinforced By Ceramic Phase Particles

In the field of metallurgy, diggings, building materials, chemical engineering, coal mine and so on, the economic loss caused by wear occupies a huge proportion of the production cost. Therefore, it has great economic and social benefits to overlay a lay of wear-resistant coating on surface of workpiece in order to increase its wear resistance. In this paper, Fe-based coatings reinforced by composite carbides of TiC-VC-Mo2C were produced by use of laser cladding and in-situ synthesis technologies on surface of low carbon steel of Q235 substrate. Moreover, microstructure and properties of the cladding coatings were systematically investigated by means of opitical microscopy(OM), X-ray diffractometer(XRD), electron probe microanalyser(EPMA), scanning electron microscopy(SEM), micro-hardness tester and dry sliding wear tester.The influences of laser cladding power, scanning speed, thickness of pre-placed powder, overlapping ratio of multi-pass layers and so on were researched on the coatings. The results showed that, the coatings were provided with excellent surface formation and fabricability with large areas when the processing parameters were at laser cladding power of 2500W, scanning speed of 5mm/s, flow rate of shielding gas of 15-20L/min, thickness of pre-placed powder of about 1.0mm and overlapping ratio of about 30%.The influences of different constituents and their contents in the alloy powders were also studied on the coatings. Plenty of carbide particles were generated with addition of alloy powders as ferrotitanium, ferrovanadium, ferromolybdenum, which played a important role in wear-resistant coating by particle strengthening. However, when the content was beyond a definite store of quantity, the melt might have higher viscosity and worse mobility, then terrible surface formation and high crack sensitivity appeared in the coating. Ferroboron addition might refine the size of ceramic particles, which changed microstructure of matrix from acicular Ferrite to Pearlite and high carbon Martensite. Ferrochromium addition could make Cr solute with Fe to form a positive effect of solution strengthening. When ferrochromium content was beyond a definite store of quantity, fragile and hard Ledeburite, which increased the crack sensitivity of the coating, emerged in the coating.Through cladding alloy powders consisted of ferrotitanium, ferrovanadium, ferroboron, ferromolybdenum, ferrochromium and so on, composite coating reinforced by hard particles of TiC-VC-Mo2C was prepared. Composite coating with excellent surface formation was slag-free and crack-free. Furthermore, it was provided with compact microstructure and was with a uniform distribution of hard ceramic particles. The abrasion mechanism of composite coating was micro-cutting and local adhesive wear caused by fatigue abscission. Composite coating owned high micro-hardness(1102.5HV03) and plastic deformation was hard to occur in it, therefore, the coating was provided with quite perfect wear properties. Under the same wear condition, the weight loss of composite coating was only about 1/20 of that of Q235 substrate.