Effect of deep cryogenic treatment on wear behaviour of Nimonic-90

The present study focuses on the effect of Deep Cryogenic Treatment (DCT) with post tempering on wear behaviour of Nimonic-90 superalloy under dry, lubricated and high temperature conditions. The results showed significant improvement in hardness and wear resistance when compared with untreated samples. The maximum percentage improvement in hardness was 56.09%. In dry, lubricated and high temperature wear conditions, the maximum percentage reduction in wear rate was 41.05%, 45.83% and 36.34% respectively. This significant reduction in wear rate was attributed to lattice contraction at cryogenic temperature raising precipitation of hard phases like carbides and reducing the grain size. This overall changes in the microstructure imparted hardness to the matrix of Nimonic-90 which significantly increases the wear resistance of Nimonic-90. Scanning Electron Microscopy (SEM) was used to observe the changes in the microstructure like reduction in grain size, carbides precipitation, shallow and deep pits after pin on disc wear test. EDAX study was also done to see the distribution of alloying elements in the microstructure. X-ray Diffraction (XRD) was conducted to observe newly developed phases along with phase fraction.