Plasma cladding coatings by precursor carbonization-composition process

A process of preparing Fe-Cr-C composite powder for precursor carbonization-composition process was developed using the compacts of mixed ferrotitanium, chromium, iron and carbon precursor (saccharose) powers as raw materials, and Fe-Cr-C and Fe-Cr-C-Ti composite coatings were synthesized and deposited on Q235 steel substrates by plasma cladding technology. The phase composition and microstructure of the composite coatings were analyzed by X-ray diffraction (XRD) and scanning electron microscopy (SEM). It is shown that the Fe-Cr-C composite coating consists of (Cr,Fe)₇C₃ primary phase, (Cr,Fe)₇C₃ eutectics with a petal-like distribution and austenite, but the Fe-Cr-C-Ti composite coating is composed of in situ TiC and (Cr,Fe)₇C₃ eutectics and austenite. The two types of composite coatings are also metallurgically bonded to the substrates. The volume content of TiC in the coating shows a gradient distribution. Generally, TiC phases in the fusion zone and central regions are equiaxed, and TiC phase in the surface is dendritic. Compared with the Fe-Cr-C composite coating, the Fe-Cr-C-Ti composite coating has better anti-cracking. The average microhardnesses of the Fe-Cr-C and Fe-Cr-C-Ti composite coatings are about 750 HV_0.2, 3.2 times as large as the microhardness of the based metal, and this value changes little from the surface to the fusion zone.