If you have delamination or brittleness between layers on PLA, try raising the temperature a little more. This is quite typical of a too low printing temperature.
However, a steel nozzle will have lower performance on “standard” materials compared to a copper/nickel nozzle. But for heavy (abrasive) materials, a copper/nickel nozzle will wear out quickly as opposed to a steel nozzle. Abrasive materials wear out materials, and the steel nozzle is resistant to this type of wear.
Therefore, as a general rule, raise the temperature of the head by 5 to 10°. As well as having a copper/nickel head for “standard” materials and a steel head for loaded (abrasive) materials.
If you want to change your nozzle but don’t know how. You can follow our advice via the topic on changing nozzles.