Fabrication of nickel/steel multilayer pipe by reactive centrifugal casting method

Abstract

Reactive centrifugal casting method could fabricate a Ni-aluminide/steel multilayer pipe. In this method, Ni powder is placed on a spinning steel pipe, and Al liquid was poured into the steel pipe. Then the Ni powder and Al liquid exothermically reacted and produced a composite layer consisting of Ni-aluminides on the inner surface of the steel pipe. The heat generated by the exothermic reaction melted the inner surface of the steel pipe and bonded the composite layer to the steel. In this study, fabrication of nickel/steel multilayer pipe by reactive centrifugal casting method is focused. However, during the above process, the Ni powder could move along the flow of the Al liquid. Moreover, sometime retained Ni powder was observed within the fabricated pipe, due to the lack of input heat. To overcome these shortcomings, in this study, Ni liquid as well as Al liquid was used for the reactive centrifugal casting method. Microstructure and ratio of joint region are studied. We focus on the effects of the pre-heating temperature and holding time, because these processing parameters can be easily controlled. Nickel layer and steel pipe are joined by the reactive centrifugal casting method under preheating-temperature from 700°C to 900°C. As preheating temperature increases, the ratio of the joint region is increased. Moreover, the ratio of the joint region is increased by heating the steel pipe under pre-heating temperature after the casting. Hence, it is found that the pre-heating and the heating after casting for the pipe are effective to join the nickel layer and the steel pipe.