Zengda Zou

Microstructure and properties of laser clad TiC+NiCrBSi+rare earth composite coatings

Abstract TiC particle reinforced Ni-based alloy composite coatings were clad to AISI 4140 chromium molybdenum alloy steel substrate using a laser. The microstructure and tribological behavior of coatings were studied experimentally by means of scanning electron microscopy, transmission electron microscopy and wear tests. Partial solution of TiC particles occurs in the laser melting pool during the heating stage. Twins and dislocations were observed at the interface of TiC particles and the matrix. The wear resistance was found to correlate with the load and amount of the TiC particles present in the clad layer. By adding La 2 O 3 , the hardness of clad coatings was significantly increased, and the wear resistance of clad coatings was enhanced.

Effects of activating flux on CO2 laser welding process of 6013 Al alloy

In order to increase the absorption of laser energy and improve the weld appearance in laser welding of Al alloy, 1.8 mm- 6013 Al alloy plate was welded by activating flux CO2 laser welding. Activating flux includes oxide and fluoride, which was coated on the workpiece surface before welding. The experimental results show that the activating flux can effectively improve the absorption of CO2 laser energy and increase the amount of the molten base metal. The improvement on the absorption of laser energy by oxide activating flux is greater than that by fluoride activating flux or two-component activating flux, but the slag detachability made from both the single activating flux and two-activating flux is poor. The gas pore sensitivity with oxide activating flux is much higher than that with fluoride activating flux in CO2 laser welding of 6013 Al alloy.

Amorphization of Fe38Ni30Si16B14V2 surface layers by laser cladding

Abstract Fe38Ni30Si16B14V2 amorphous composite coatings were fabricated by laser cladding on AISI 1045 steel in order to increase the wear resistance. The phase and microstructure of the coatings were analyzed by X-ray diffractometry and transmission electron microscopy. The wear properties of the coatings were also investigated by means of sliding wear test. The results show that the coating consists of amorphous phase in majority and nanocrystalline phase in minority. The amorphous coatings can be obtained while the scanning speed is 3 500 mm/min and the laser power is 4.8 kW. With increase of the laser power, the amorphous phase in the coating increases when it is lower than 4.8 kW. A gradient distribution of the microhardness ranges from Hv0.2 1 208 to Hv0.2 891 in the coating from top surface of the coating to the substrate. The amorphous coating is found to possess better property of wear than AISI 1045 steel substrate.