Micro-structural design had attracted increasing interests in modern developments of hard coatings. The ability of cold spray process to retain the feedstock microstructure into coating makes it possible to design coating microstructure through feedstocks for development of different coating properties. In this study, a multi-size modal WC-12Co powder containing nano-sized WC particles was designed to deposit WC-Co deposition with multi-sized WC. Multimodal WC-12Co powders were prepared with ball-milling of a commercial WC-12Co powder, cold-compacting, sintering in hydrogen atmosphere and crushing. WC particle size in the powder exhibits a distribution with two peaks in tens of nanometers and several micrometers. The multimodal WC-12Co deposition was prepared by cold spraying using helium as driving gas. The multimodal size of WC particles in the powders was retained into the deposit. The micro-hardness and fracture toughness of the multimodal structured WC-12Co deposit was compared with bulk WC-12Co. It was found that the multimodal deposition exhibits a comparable hardness to nano-sized WC-12Co and a high fracture toughness compared with micro-sized WC-12Co. The simultaneous strengthening and toughening of WC-12Co can be realized through the bimodal microstructure design of WC-Co.

FeAl Intermetallic compounds have excellent wear resistance and high temperature oxidation resistances. The low temperature brittleness makes intermetallic compound materials more suitable to be applied in the form of coating to protect materials from high temperature oxidation and wear. In the present study, a iron/aluminum composite coating was produced by cold spraying of iron and aluminum powder mixtures and then was annealed at different temperatures to aim at forming an iron aluminide intermetallic based coating. The deposition behavior of iron and aluminum powder mixtures and microstructural characteristics of the as-sprayed deposit were examined by scanning electron microscopy (SEM). The kinetics of the phase transformation of the as-sprayed iron/aluminum composite deposit to iron aluminide was characterized by differential scanning calorimetry (DSC) and X-ray diffraction (XRD). The results showed that after heat treatment at a temperature of 600°C, intermediate phase Al 5 Fe 2 coexisted in the deposit with remaining Fe and Al. With increasing heat treatment temperature to 900°C, the deposits consisted of mainly FeAl phase and a trace of remaining Fe phase.