Shiyao Qu

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.

Microstructure and Wear Properties of Laser Clad (Ti,Mo)C Multiple Carbide Reinforced Fe-Based Composite Coating

(Ti,Mo)C multiple carbide reinforced Fe-based composite coating was produced by laser melting a precursor mixture graphite, ferrotitanium (Fe―Ti), andferromolybdenum (Fe―Mo) powders. The results showed that flowerlike and cubic type (Ti,Mo)C multiple carbides were formed during laser cladding process. The selective area diffraction pattern analysis indicated that (Ti,Mo)C crystallizes with cubic structure, which indicates that (Ti,Mo)C carbides were multiple carbides with Mo dissolved in the TiC structure. The formation of (Ti,Mo)C particles was achieved via a nucleation-growth mechanism during the laser cladding process. Increasing the amount of Fe―Mo in the reactants led to a decrease of carbide size and an increase of volume fraction of carbides. The coating possessed good cracking resistance when the amount of Fe―Mo was controlled within a range of 15 wt %. The Fe-based surface coating reinforced by (Ti,Mo)C multiple carbides gave an excellent wear resistance.