Field Test Error of Leeb Hardness of Bolt Fasteners

The Brinell hardness (H_BW) and the Brinell hardness converted from the tested Leeb hardness (H_LD→B) of as-serviced In783 high-temperature alloy and 1Cr11Co3W3NiMoVNbNB steel bolt fasteners were tested at heads and waists respectively under different conditions (polishing state and grinding state), and the difference between H_BW and H_LD→B at different parts and under different conditions were studied combined with the microstructure observation. The results show that at the same test position (head or waist) of the two bolts, the hardnesses of the polished samples were higher than those of the ground ones. Under the same test condition (polishing or grinding), the hardnesses of the bolt heads were higher than those of the waists. The H_LD→B (grinding state) of the In783 high-temperature alloy bolt were evidently different from the H_BW (polishing state) at the same part, and the former was about 4% reduction. This error needed compensating when field test. The relationship between H_BW (polishing state) and H_LD→B (grinding state) of the 1Cr11Co3W3NiMoVNbNB steel bolt was H_BW=1.06-1.10H_LD→B, which indicated that for the low-carbon and high-alloy steel there was also a negative deviation compared H_LD→B to the actual tested H_BW.