Cobalt-free Hard-facing for Reactor Systems

钴基（Co）合金广泛用于核反应堆中，特别是在易于磨损和擦伤的区域，例如阀门和泵。这是因为它们具有出色的耐磨性，从而延长了部件寿命并降低了维护要求。然而，这些合金是核设施工作人员大部分辐射暴露的原因，因为形成了钴-60，一种伽马放射性同位素。出于这个原因，在未来的核反应堆中替换钴基耐磨堆焊合金是非常可取的。对于目前的印度原型快中子增殖反应堆（PFBR），镍基（Ni）合金已被用作替代品，但这些合金价格昂贵且非常容易开裂。一类新的铁（Fe）基硅化物强化系统已显示出巨大的堆焊应用潜力。针对PFBR中需要堆焊的部件的规模，提出了等离子体转移弧（PTA）沉积，这是一种高度灵活的制造技术，可替代HIP焊接。然而，迄今为止，Fe硅化物强化合金的PTA制造还有待探索。实际上，PTA加工镍（Ni）基合金产生的残余应力（形成不可接受的裂纹和缺陷的关键驱动因素）仍有待理解。PTA工艺的成功表征、优化和模拟以及在铁基合金系统中的应用是从核电站中消除钴的关键一步。

Cobalt-based (Co) alloys are extensively used in nuclear reactors, particularly in regions prone to wear and galling such as valves and pumps. This is because they provide outstanding wear resistance, and so improve component life and reduce maintenance requirements. However, these alloys are responsible for a large portion of the radiation exposure of workers at nuclear utilities, due to the formation of Cobalt-60, a gamma-emitting radioactive isotope. For this reason, replacing Co-based hardfacing alloys in future nuclear reactors is highly desirable. For the current Indian prototype fast breeder reactor (PFBR) Nickel-based (Ni) alloys have been used as an alternative, however these alloys are expensive and very susceptible to cracking. A new class of Iron (Fe) based, silicide strengthened systems have shown great potential for hardfacing application. In response to the scale of components that require hardfacing in the PFBR, plasma transfer arc (PTA) deposition is proposed, a highly flexible manufacturing technique, as an alternative to HIPbonding. To date, however, PTA manufacturing of Fe silicide strengthened alloys is yet to be explored. Indeed, the residual stress resulting from PTA processing nickel (Ni)-based alloys, a key driver in the formation of unacceptable cracks and defects, is still to be understood. Successful characterisation, optimisation and simulation of the PTA process and application to Fe based alloy systems is a key step in eliminating Co from nuclear plant.