Cluster induced quenching of galaxies in the massive cluster XMMXCSJ2215.9-1738 at z~1.5 traced by enhanced metallicities inside half R200

(Abridged) We explore the massive cluster XMMXCSJ2215.9-1738 at z~1.5 with KMOS spectroscopy of Halpha and [NII] covering a region that corresponds to about one virial radius. Using published spectroscopic redshifts of 108 galaxies in and around the cluster we computed the location of galaxies in the projected velocity vs. position phase-space to separate our cluster sample into a virialized region of objects accreted longer ago (roughly inside half R200) and a region of infalling galaxies. We measured oxygen abundances for ten cluster galaxies with detected [NII] lines in the individual galaxy spectra and compared the MZR of the galaxies inside half R200 with the infalling galaxies and a field sample at similar redshifts. We find that the oxygen abundances of individual z~1.5 star-forming cluster galaxies inside half R200 are comparable, at the respective stellar mass, to the higher local SDSS metallicity values. The metallicities of these galaxies in the inner part of the cluster are higher by 0.1-0.2dex, at a given mass, than those of infalling galaxies and of field galaxies at z~1.5. This effect is more pronounced when using the O3N2 metallicity calibration compared to the N2 calibration, which can be explained by the different locations of cluster and field galaxies in the [OIII]/Hbeta vs. [NII]/Halpha diagram involving two line ratios compared to one line ratio information in the case of the N2 relation. The enhanced metallicities of cluster galaxies at z~1.5 inside half R200 indicate that the density of the ICM in this massive cluster becomes high enough toward the cluster center such that the ram pressure exceeds the restoring pressure of the hot gas reservoir of cluster galaxies and can remove this gas reservoir initiating quenching, although the galaxies continue to form stars, at slightly lower rates, using the available cold gas in the disk which is not stripped.