Development of Erosion Resistant Claddings for Helicopter Rotor Blades.

摘要

The objective of this program is to optimize the Solar boriding process to obtain a well supported boride on a metallic substrate (clad) and to evaluate the erosion resistance and other critical properties of a clad substrate. Processes were also developed for adhesive bonding the cladding to the leading edges of helicopter rotor blades. Test results demonstrated that dense boride coatings on steel and titanium alloys can reduce the dust erosion rate,compared to uncoated metal,by 30to several hundred fold. Overall the borided titanium alloy clad appeared most favorable of the four clad alloys evaluated. The extreme hardness of TiB2afforded essentially complete erosion protection with a coating thickness of only 0.0005inch. Resistance to rain erosion,impact,and saline water corrosion also favored the titanium alloy. Of the steels,the alpha alloy,SAE 430,was best in performance in erosion,impact and saline water corrosion. Performance of the boride coated 430and Ti-6Al-4V alloys in rain erosion tests was excellent. The use of a boride coated metallic cladding to reduce rain and dust erosion to extremely low levels was demonstrated. Forming of SAE 430and Ti-6Al-4V alloys before boriding,maintaining dimensions during boriding,and the subsequent adhesive bonding of the borided shapes to sections of metallic and glass-epoxy rotor blades was shown to be feasible.