Hard-yet-tough high-vanadium high-speed steel composite coating in-situ alloyed on ductile iron by atmospheric plasma arc

Abstract

Hard-yet-tough high-vanadium high-speed steel composite coating in-situ alloyed on ductile iron by atmospheric plasma arc Cao, Huatang; Dong, Xuanpu; Pei, Yutao T. Take-down policy If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim. H. Cao, et al., Int. J. Comp. Meth. and Exp. Meas., Vol. 6, No. 3 (2018) ABSTRACT A graded high-vanadium alloy composite coating was synthesized from premixed powders (V, Cr, Ti, Mo, Nb) on ductile iron (DI) substrate via atmospheric plasma arc surface alloying process. The resulted cross-section microstructure is divided into three distinct zones: upper alloyed zone (AZ) rich with spherical primary carbides, middle melted zone (MZ) with fine white iron structure and lower heat affected zone (HAZ). Spherical or bulk-like primary carbides with diameter < 1 μm in the AZ are formed via in-situ reactions between alloy powders and graphite in DI. Microstructural characterizations indicate that the carbides are primarily MC-type (M=V, Ti, Nb) carbides combined with mixed hardphases such as M 2 C, M 7 C 3 , M 23 C 6 , and martensite. Disperse distribution of spherical, submicron-sized metal carbides in an austenite/ledeburite matrix render the graded coating hard-yet-tough. The maximum microhardness of the upper alloyed zone is 950 HV 0.2 , which is five times that of the substrate. Significant plastic deformation with no cracking in the micro-indentations points to a high toughness. The graded high-vanadium alloy composite coating exhibits superior tribological performance in comparison to Mn13 steel and plasma transferred arc remelted DI.

Hard-yet-tough high-vanadium hierarchical composite coating: Microstructure and mechanical properties

“…It also indicates that the spacing between the MC carbides can be < 200 nm, which meets the criterion for the Orowan strengthening mechanism usually operating at an inter-particle distance < 500 nm depending on the size [54]. Furthermore, apart from the submicron-sized (primary) MC, in the HVHSS coating there are still numerous ever smaller nano-sized (eutectic) MC carbides [40,55] that potentially pin the dislocations leading to reinforcement.…”