Abstract
The microstructure evolution, elements diffusion and fracture behavior of the Stellite 6 weld overlay, deposited on 10Cr9Mo1VNbN (F91) steel by the tungsten inert gas (TIG) cladding process, were investigated after long-time service. Obvious diffusion of Fe occurred from the steel and fusion zone to the Stellite overlay, resulting in the microstructure evolution and hardness increase in the coating, where hard Co–Fe phases, σ phases (Fe–Cr metallic compounds) and Cr-rich carbides (Cr18.93Fe4.07C6) were formed. Besides, the width of the light zone, combined with the fusion zone and diffusion zone, increased significantly to a maximum value of 2.5 mm. The fracture of the Stellite coating samples mainly occurred in the light zone, which was caused by the formation and growth of circumferential crack and radial crack under high temperature and pressure conditions. Moreover, the micro-hardness values in the light zone increased to the maximum (470–680 HV) due to the formation and growth of brittle Co–Fe phases. The formation of these cracks might be caused by formed brittle phases and changes of micro-hardness during service.
Highlights
10Cr9Mo1VNbN (F91) steel, as a martensitic, heat-resistant steel, has outstanding high-temperature performance and corrosion resistance, and is massively applied in manufacture of steam boiler, valve body, tube and turbine components [1]
Different overlaying methods have been performed to investigate the properties of the wearing coating, including laser cladding, arc welding, plasma transferred arc (PTA) welding and gas dynamic cold spray [5,6,7,8,9,10,11,12,13,14]
The microstructure of the Stellite weld overlay zone (WOZ) was a typical dendritic in Figure 2b, which consisted of Co solid solution and a network of small carbides particles
Summary
Stellite alloy (Co-based alloy), especially Stellite 6 alloy, is often used as a coating material in valve disc manufacturing, due to its excellent wear resistance, corrosion resistance and high temperature properties [2,3,4]. Different overlaying methods have been performed to investigate the properties of the wearing coating, including laser cladding, arc welding, plasma transferred arc (PTA) welding and gas dynamic cold spray [5,6,7,8,9,10,11,12,13,14]. Kusmokoet et al [15] deposited the Stellite 6 alloy on P22 steel and P91steel plates by laser cladding and investigated the sliding wear characteristics of the coating
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
