Wear behaviour of boronized and duplex-treated AISI 4140 steel against DLC-coated boronized AISI 4140 disc

Abstract

Wear behaviour of the AISI 4140 steel specimens with various surface conditions was tested against the DLC-coated boronized disc of AISI 4140 steel. Specific wear rate and coefficient of friction (COF) of the as-boronized (AB) pins at 100 and 150 N loads were substantially lower than the boronized–polished (B-P) pins. COF of AB pins was in the range of 0.07–0.09. However, the COF of B-P pins was about 0.13. In case of the DLC-coated pins, underlying boronized surface outperformed the hardened–tempered surface. Wear properties of the DLC-coated pins were improved with an increase in the load. DLC coating on both contacting surfaces gave the lowest specific wear rate of 0.21 × 10⁻⁸ mm³ N⁻¹ m⁻¹, which was about 30 times lower than the B-P pins, and COF was in the range of 0.08–0.09.