Effects of superplasticity in boronizing of duplex stainless steel

In this research, conventional boronizing process (CB) and a new method of boronizing process under compression load condition (LB) were conducted and compared in order to study the effect of superplasticity on boronized substrate. Both processes were conducted on duplex stainless steel (DSS) with two different rnicrostrUctures; as-received DSS with coarse grain microstructure (CDSS); and thermo-mechanically treated DSS with fine grain microstructure (FDSS) which can show superplastic behavior at high temperatures. Both processes were conducted at duration of 6 hours and temperatures between 1123 and 1223 K. All of boronized specimens demostrated thin, smooth and compact morphology of boride layer. For CDSS, both CB and LB processes produced about similar surface hardness values within the range of 1425 - 2330 HV For FDSS, CB process produced Surface hardness between 1522 and 2601 HV, while under LB, the highest surface hardness Values in the range of 1659 - 2914 HV were obtained. The result shows that introduction of load during boronizing has initiated superplastic deformation on FDSS thus accelerated diffusion of boron atoms into surface which finally lead to significantly higher surface hardness.