Nitriding Layer Without White Layer Prepared on H13 Steel Surface and Its Abrasive Resistance

H13 steel was nitrided using plasma nitriding technique. The nitriding layer with different composition and thickness was obtained by changing nitriding pressure and temperature. The microstructure and phase composition of the nitriding layers were studed by optical microscopy and X-ray diffractometer respectively. The tribology property of the nitriding layer against Al2O3 ball was performed on a ball-disc abrasion tester in air. The results show that the nitriding layer mainly constituted of ε-Fe2-3N, γ′-Fe4N and a few α-Fe, Fe2O3 and Fe3O4 phase. There was not obvious nitriding layer when nitriding temperature was 510 ℃, the nitriding layer had only diffusion layer when nitriding temperature was 570 ℃ and pressure was 200 and 300 Pa and nitriding temperature was 540 ℃ and pressure was 100 Pa. The nitriding layer constituted of white layer and diffusion layer under other conditions. The surface hardness after nitriding was 1100-1200 HV, double the stbstrate. Comprising with substrate, the friction coefficient reduced greatly at the temperature of 570 ℃ and the pressure of 200 Pa, wear mark became wide, specific wear rate decreased obviously and abrasive resistance improved significantly.