BaF2·CaF2-Cr3C2-NiCr (denoted as BCF).Fig.1(a)-(d) shows the surface morphologies of BCF powder, Ag powder and physically blended 10Ag-BCF composite powder. It can be seen that BCF particles mainly appear as hollow spheres(see Fig.1(a)), which are typical morphology of spray-dried and sintered particulates.Ag particles prepared by gas atomization exhibit spherical or near-spherical shape(see Fig.1(b)). Fig.1(e) shows the particle size distribution of physically blended 10Ag-BCF composite powder. The particle sizes of 10Ag-BCF composite powder are mainly in the range 22.3-57.7um. After blending,10Ag-BCF composite powder retains the characteristics of BCF and Ag particulates without apparent crushing or deformation, and possesses good flow ability and required particle sizes for HVOF spraying process(conventional particle size for HVOF spraying:5-45 um [6]). Fig.1() shows the XRD patterns of physically blended 10Ag-BCF composite powder and BCF powder for comparison.The BCF powder mainly consists of CraC2(JCPDS card No.35-0804) and Ni(JCPDS card No.04-0850), and the Ni peaks are shifted to lower 20 position in comparison to the reference pattern, which should be attributed to alloying with Cr. Aside from CraC2 and Ni phases, BCF powder also includes small amounts of BaF2(JCPDS card No.04-0452) and CaF2(JCPDS card No.77-2245) as designed. However, unexpected weak signals of Cr2O3(JCPDS card No.38-1479) were also detected in the powder.10Ag-BCF composite powder contains the above mentioned phases in BCF powder and the incorporated silver (JCPDS card No.89-3722).
Fig.1. SEM images of (a) BCF powder,(b) Ag powder and(c)(d)10Ag-BCF composite powder;(e) particle size distribution and (f) XRD patten of 10Ag-BCF composite powder.
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