Three various 12CrNi2 alloy steels were successfully fabricated on 35CrMo alloy steel by laser melting deposition with the aim of investigating the effect of powder oxygen content on formability of 12CrNi2 alloy steel. The phase constituents, macroscopic morphology, microstructure, and microhardness of powders and samples were studied by some modern analysis methods. The experimental results showed that with the increase of the oxygen content from 220 to 600 ppm, the sphericity and density of the powders gradually decreased which led to the appearance of pores in the as-deposited samples. The phase constituent of three as-deposited samples with different oxygen contents was α-Fe(M) phase. The percentage porosity in the macroscopic morphology increased with the increase of the oxygen content. Meanwhile, the high oxygen content contributed to more pores and the crack formation in the microstructure. With the increase of oxygen content, the microhardness of the as-deposited samples would decrease.

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Co-based alloy cladding layers (wallex50 and wallex55) were synthesised on 316L stainless steel by vacuum cladding. Experimental results showed that wallex50 composed of γ-Co, WC, Co 6 W 6 C, Cr 7 C 3 , in which in situ reinforcement WC phases were homogeneously distributed in the layer, having a clear and stable interface structure. Wallex55 with externally added WC particles was composed of γ-Co, WC, Co 6 W 6 C, Cr 7 C 3 , CrB, CoWB. The average microhardness of wallex50 and wallex55 was 794 ± 29 and 939 ± 24 HV, respectively. Nevertheless, wallex50 showed a better resistance to friction and wear than wallex55, which was not in a cross line with Archard's law. Relative wear resistance of wallex50 was 23.36, which was 1.56 times greater than that of wallex55. The improvement of friction and wear for wallex50 could be due to the fact that the in situ synthesised WC particles increased the friction and wear resistance by the pinning effect of the retained reinforced phase on the Co-based matrix.

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