Heat treatment processes for hardening a workpiece such as a turbine blade include attaching a spacer to a workpiece surface, wherein the spacer comprises an inner profile mirroring the workpiece surface and an outer profile effective to generally uniformly distribute heat to the workpiece surface, heating the spacer to uniformly heat the workpiece surface at a temperature effective to form an austenitic microstructure in the workpiece surface, cooling the workpiece surface at a rate effective to transform the austenitic microstructure to a martensitic microstructure, and removing the spacer from the workpiece prior to or subsequent to cooling.