Study On The Wear-resistance And Corrosion-resistance Of Ni-Cr-B High Boron Alloy

High boron alloy is a kind of widely applicable wear-resistant alloy, in which in-situ synthesis borides is obtained to improve its wear-resistance. However, many parts require both wear-resistance and corrosion-resistance under some typical conditions, such as screws of the inject machine. In this paper, Ni-Cr-B high boron surfacing alloy powder agglomates was designed, including Ni-Cr-B-Mo alloy powder agglomates and Ni-Cr-B-Fe alloy powder agglomates. The microstructure, phase, wear-resistance and corrosion-resistance of the deposited metal were systematically investigated. The results are as follows:Ni-Cr-B-Mo and Ni-Cr-B-Fe deposited metal both had the rapid cooling directional solidifying Microstructure. There was an obvious metallurgical transition zone between the deposited metal and the substrate.There was obvious hypereutectic structure in the top of Ni-Cr-B-Mo deposited metal. The main hard phase in the deposited metal is ternary boride MoM’B2, in which M’is the metal element including Fe, Ni, Cr. When there was the same B content in the Ni-Cr-B-Mo deposited metal, there were the fewest ternary borides in the Ni-Cr-B-Mo deposited with 44% Mo content. No matter when the content of Mo increased or decreased, the number of ternary borides in the Ni-Cr-B-Mo deposited metal increased, and the ternary borides had completely different shapes with different Mo content. The microhardness of ternary borides was far higher than the eutectic structure in Ni-Cr-B-Mo deposited metal.With the increase of the Mo content, the microhardness of ternary borides and the eutectic structure decreased. When the Mo content was 37.53%, the microhardness of ternary borides was the highest. With the increase of the Mo content, the corrosion-resistance of the Ni-Cr-B-Mo deposited metal improved. However, when the Mo content was more than 44.18%, the corrosion resistance didn’t improve obviously.The main hard phase in the deposited metal was the lath-like and net-like complex boride (Fe,Cr,Ni)2(B,C), which has the structure of Fe2B. With the content of Fe-B alloy powder increasing, the number of the boride increased. When the content of the Fe-B alloy powder was more than 50%, B appeared in the deposited metal. The microhardness of the Ni-Cr-B-Fe deposited metal increased with the content of the Fe-B alloy powder increasing, but it didn’t increase obviously. The corrosion-resistance of the Ni-Cr-B-Fe deposited metal improved with the content of the Fe-B alloy powder increasing.The corrosion-resistance of the Ni-Cr-B-Fe deposited metal with 50% Fe-B alloy powder content was worse than that of Ni-Cr-B-Mo deposited metal. When the content of the Fe-B alloy powder was 50%, borides had the shape of laths in the deposited metal with 5%Cr. And there were also net-like and honeycomb boride in the deposited metal with 10%Cr. When the content of Cr was 15%, the borides appeared as long strips, which were parallel in short range. The microhardness of the deposited metal increased with the content of Cr increasing. When the content of Cr was 15%, the microhardness of the boride was up to 1252.3HV, much higher than the eutectic structure. Moreover, the corrosion-resistance of the deposited metal with 15% Cr behaved best.The wear-resistance of all kinds of the deposited metal was much better than the substrate Q235 steel. The mass loss of the Ni-Cr-B-Mo deposited metal with 37.53%Mo content was 27.7 times that of Ni-Cr-B-Fe deposited metal with 50% Fe-B alloy powder content. Therefore, Ni-Cr-B-Fe deposited metal had the worse wear-resistance.The wear-resistance of Ni-Cr-B-Fe deposited metal improved to a certain extent with the content of Fe-B alloy powder increasing. When the content of Cr was up to 15%, The wear-resistance of Ni-Cr-B-Fe deposited metal got worse.