The comparative study of thermal fatigue behavior of laser deep penetration spot cladding coating and brush plating Ni-W-Co coating

For improving the thermal fatigue behavior of hot work die steel in engineering application, the present work compare the influence of thermal fatigue resistance by the two different surface modified processes, the laser deep penetration spot cladding (LDPSC) and brush plating on the Cr12MoNi hot rolling tool steel. The thermal fatigue tests were fulfilled by heating and quenching in water at a cycle period of 2 min. Before and after thermal fatigue testing, the microhardness distribution profile and microstructure of LDPSC have been investigated. The results show that the LDPSC can be divided to three zones: cladding zone, alloying zone and heat affected zone. The major phases in cladding zone consist of Fe3C, Cr7C3, Cr23C6 and martensite. The oxidation resistance and thermal stability of brush plating Ni-W-Co coating and reference materials has been determined. The results of thermal fatigue testing show that LDPSC and brush plating Ni-W-Co coating can improve thermal fatigue resistance as compared to the reference material. The brush plating Ni-W-Co coating is more effective than the former owing to its higher thermal stability, oxidation resistance, superfine grain, high-density dislocation in microstructure and combination of strength and ductility.