Effect of Nitriding and Nitrocarburizing on the Hardness, Tribological and Corrosion Behaviour of GS-42CrMo4V Steel in Mining Applications

Abstract-The GS-42CrMo4V steel is designed to be used in highly loaded mining components, where surfacedegradation can occur due to combined mechanical and environmental influences. This study compares a referencebase-metal condition (BM), nitrided condition (N) and nitrocarburized condition (NC) using hardness, standardisedthree-body abrasion, linear reciprocating wear and potentiodynamic polarisation in 3.5 wt.% NaCl. The measuredhardness improved from 450 HV for BM to 578 HV and 585 HV for N and NC, respectively. Volume losses obtainedthrough ASTM G65 testing were 192.83, 171.51 and 129.92 mm³ for BM, N and NC, respectively. This resulted in anoverall reduction of 11.06% and 32.62% relative to BM. For linear reciprocating tests performed with a load of 25,50 and 75 N and temperatures of 30, 60 and 90 °C, results indicate a high dependency on test severity. Volume lossreduced from 0.524 mm³ for BM to 0.361 mm³ for N and 0.284 mm³ for NC at 90 °C and 75 N. Corrosion currentdensities in 3.5 wt.% NaCl were 1.597, 13.277 and 7.198 µA cm⁻² for BM, N and NC, respectively. These findingsshow that hardness and abrasive/sliding wear resistance improvements do not always result in a consistentimprovement in electrochemical corrosion resistance. It shows the need to choose a suitable thermochemical surfacetreatment depending on the predominant modes of degradation and environment.