While it is possible to advance the power levers all the way to the "stop" and damage an engine, there are several factors that need to be considered.
1) The fuel control units function is to regulate or meter the proper amount of fuel given the rate at which the power levers are advanced or retarded. During power advancement the FCU prevents an excess amount of fuel from entering the combustion section and causing damage to the engine.
2) Turboprop engines also have limits as to how much torque can be applied to the engine. Some airframes are torque limited due to rudder limitations in the single engine regime. However, the pilot must observe these torque limitations. Too much torque can cause damage to the engine under certain conditions.
3) Inter Turbine Temperature is also a limiting factor. This is the amount of heat that the turbine can withstand before damage is done to the turbine blades themselves. Typically the ITT is about 680 degress Celsius. I saw the result of this about 12 years ago when the crew of turboprop exceeded the ITT for some 10 minutes by about 175 Celsius. The first and second stage turbine blades were severly damaged. The engine had to be shut down in flight; and was later relegated to the classroom as an expensive exibit!
The limitations section of the Pilot Operating Handbook, also called the Airplane Flight Manual will list the Limitations (section 2) for the engine, and these must be strictly adheared to. Also the pilot should consult the Performance section of the POH/AFM (section 5) for further information regarding the operation of the engines.
In short, is it possible to melt the engine? If one had a malfunctioning FCU, did not observe the torque and ITT limits, I am sure that the engine could be "melted" to some extent, and in any event severe damage of some sort would be the result.
Hope this helps