Unlock only when you need some specific look or taking artistic license. That's more accurate to how materials behave. Lock your Fresnel IOR in Reflect and only use the Refract IOR. Render 2 chrome spheres next to each other and set the max to 1 and you'll see it reflects and goes black, now set the max to 5 or 10 and you'll see more layers of reflection between them (like an infinity mirror). That's really only for when you are using a lot of reflective/refractive objects (like lots of glassware or metal near each other) and you need more bounce calculations for that. Make a new default VrayMtl and don't adjust the max depth for reflect (or refract). The settings I can see on your material look a little outdated or incorrect. The background is blowing out either from exposure settings or masking it out in post later. When you look at a typical setup the lights are only as large as they need to be for the size of the object. Shrink the size of the lights (using the modifier not scale tool) so you allow more of the black area beyond your setup in. You've got several large lights with a light color infinity cove and that is contributing to lack of contrast overall. What version of vray are you using? Check your gamma settings and if your working in 2.2 and your SRGB is set correctly in the VFB window.

Vray mtl wrapper 3ds max