Hi,
Here is a link to the service manual for your laptop.
https://download.lenovo.com/consumer/mobiles_pub/lenovo_y40_50_series_hmm.pdf
Scroll to p.74 to view the necessary pre-requisites and then the procedure to remove the hinge cover.
Here is the part number for the hinge cover, 5CB0F78794 (p.95)
Here is a link to just one supplier of the part. It is not a recommendation to use them. It is shown to give an idea of the price. There are others online that may suit you better. Just search online, ''using the part number only'', to get results.
http://www.ebay.com/itm/5CB0F78794-Lenovo-Y50-70-59445083-Hinge-Cover-Grade-A-/172027021342
Hopefully this is of some help.