EFFECT OF NIOBIUM ON WEAR-RESISTANCE OF 15-PERCENT CR WHITE CAST-IRON

Niobium addition to 15%Cr white cast iron can increase its wear resist ance because (1) Nb forms extremely hard carbides (NbC) of hardness ar ound HV 2400, (2) Nb can raise the matrix hardness of 15%Cr iron from HV 693 to HV 899, (3) Nb shifts the eutectic point to the right, there fore the iron can have a high carbon content without the danger of for ming brittle hyper-eutectic carbides, and (4) the morphology of NbC is block-hook-like. The NbC particles can be kept firmly in the matrix d uring the wear process. The wear resistance was tested by wet rubber w heel abrasion tests. The optimum chemical composition of the iron foun d in these tests was used for making slurry pump components, which wer e field tested in a mineral mine. The field test confirmed the laborat ory test results.