Microstructure and properties of in situ synthesized TiC-TiB₂/Fe composite coatings by TIG cladding

In this paper, in situ generated TiC-TiB₂ reinforced Fe based composite coatings were prepared on the surface of Q235 steel using tungsten inert gas (TIG) cladding from G302 alloy powder, FeTi70 powder and B₄C powder. The coatings were characterized by a series of testing methods. The results showed that the metallurgical reaction fully finished during the TIG cladding. The TiC, TiB₂ and M₇C₃ reinforced phase generated in cladding layer. The microstructure presented gradient distribution characteristics with the hard phases increasing gradually from the interface between the parent metal and the cladding layer to the surface of cladding layer. The hardness of cladding layer increased with increasing the proportion of FeTi70 and B₄C powders. When the mass ratio of G302: FeTi70: B₄C =6:3:1, the maximum hardness of sample was 976 HV0.1, which was about 5 times of the parent metal hardness. The coatings showed great wear resistance when sliding with the GCr15 steel. The wear loss of the coatings was about 1/30 of the Q235 steel, and no plastic deformation traces were found on the wear surface of coatings. The hard ceramics phases in the coating, such as TiC and TiB₂, played a wear resistance role.