Effect of processing on microstructure and properties of CoCrMoSi alloy

Abstract

CoCrMoSi alloys microstructure is affected by processing and their properties have been associated with the high volume fraction of Laves phase. However, not much has been reported on the effect of structure refinement and morphology on the properties of these alloys. This paper evaluates a CoCrMoSi alloy processed by centrifugal casting and Plasma Transferred Arc (PTA) hardfacing, aiming to understand the correlation between microstructure and properties at room temperature in the as-processed condition and following exposure at 600 °C. Characterization was carried out using scanning electron microscopy, X-ray diffraction, hardness and wear tests. The cooling rates associated with each of the processing techniques used account for the developed microstructures and associated hardness, a 626 HV 0,5 cast alloy and 649 HV 0,5 deposited alloy, the former exhibiting a coarser microstructure. Wear behavior was determined by the dispersion of solid solution areas in the microstructure and as a consequence temperature exposure aggravated the poorer wear resistance of the cast alloy. The finer phase dispersion formed in coatings overlapped the deleterious effects of dilution and account for the stable wear behavior after temperature exposure.

Influence of Processing on the Microstructure and Properties of CoCrMoSi Alloy PTA Coatings

“…Results were in line with previous reports obtained on the cast CoCrMoSi T400 alloy [10]. Dilution increase from 18 -26% promoted an increase of 27.6% on wear mass loss rate and, finally, 38% dilution resulted in the increase of 41.7% on wear rate (Figure 8b).…”

“…The findings of this macroscopic evaluation are consistent with the prediction of the literature [8]. However, limited data are available regarding the interaction of the Tribaloy T400 with the substrate (dilution) and its effect on the chemical composition, microstructure and properties of the coatings [5,10].…”

“…It might suggest that Iron, Chromium and Nickel contents variation due to dilution did not alter the developed phase, but just their proportion, following the same trend as observed recently on cast alloy, as shown in Figure 2 [5,7,10].…”

“…For the higher dilution (38%) of the coatings processed with 180 A, eutectic volume fraction decreased even more (6%) leading to the lowest hardness. Thus, the hardness was influenced first by the volume fraction of the hard phase (eutectic lamellar containing Laves phase) followed by the reduction of alloying in solid solution, following the same behavior previously observed on cast alloy [6,7,10]. Table 4.…”

Effect of Track Overlap on the Microstructure and Properties of the CoCrMoSi PTA Coatings

“…The production of welded coatings must consider the interaction between the deposition alloy and the substrate, as higher dilution induces lower hardness of the coatings. This reduction in hardness has been attributed to several factors, including the participation of the chemical elements (such as iron, chromium and nickel) from the steel substrates [10][11][12] . Coatings are largely studied by way of dilution on single track deposits processed with different deposition current 10,11 .…”