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In order to effectively improve erosion resistance and evaluate the effects of an oxy layer on AISI H13 tool steel after the oxynitriding process, this study used three different nitriding surface treatments, namely oxynitriding process 1 (using air), oxynitriding process 2 (using steam) and normal gas nitride. To evaluate the effects of microstructure and the erosion resistance of AISI H13 tool steel after different nitride processes, evaluated micro hardness, erosion tests and SEM microstructure inspections were conducted. Experimental results showed that the oxide layer can protect and improve the aluminum erosion for AISI H13 tool steel. Erosion tests of 2 and 4 h for oxynitriding process 1 could produce a thicker and complex oxide layer, which has higher hardness (HV 1021.9) and optimal weight loss (0.16 %). This procedure is proven to effectively reduce the ratio of Al-Fe-Si compounds during the A380 alloy erosion test.KEY WORDS: erosion resistance; AISI H13 tool steel; oxynitriding; A380 alloy. 421© 2009 ISIJ erosion test as shown in Fig. 1(b). The specimen was then dipped in aluminum alloy A380 for melting and maintained at 1 023 K. The rotational speed of the specimen was kept at 50 rpm. The dip time was 2 and 4 h for specimens to evaluate the erosion resistance and weight loss. After removing the aluminum, the specimens were cleaned with NaOH to remove oxide or other residues. The weight loss percentage of the erosion test was calculated as follows:IW is the initial weight and AW is the weight of after erosion test. In the experiment, three different kinds of surface treatments were: 1) normal gas nitriding: at temperature of 843 K for 1 h; 2) oxynitriding process 1: gas nitriding was carried out at temperature of 843 K for 1 h, and air oxidation at 823 K for 3 h; 3) oxynitriding process 2: gas nitriding was carried out at temperature of 803 K for 1 h, and steam oxidation at 798 K for 1 h. To evaluate the effects of erosion resistance on AISI H13 tool steel by nitriding process, erosion test, surface hardness and microstructure inspections were performed. Microhardness tests were measured by HV with loading of 200 g, which complied with the CNS 2115 Z8004 standard. Results and DiscussionThe microstructure of AISI H13 tool steel substrate obtained after quenching and tempering processes is shown in Fig. 2. This is the typical microstructure obtained through commercial heat treatment, which comprises the structure of tempered martensite and proeutectoid carbides. Figure 3 shows the microhardness test of AISI H13 tool steel after gas nitriding and different oxynitriding treatments. Gas nitriding was done with ammonia, decomposition NH 3 was used to dilute the ammonia so that it was not too aggressive. Normally, pure decomposition NH 3 is used to reduce the compound layer (white layer). Both carbon content and alloying additions raise surface hardness, thereby enhancing wear resistance. The actual hardness of the compound layer is usually substantially higher. However, a better thickness of the compound l...

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This study investigated 30Al-Si, Al-Cu, AlFe, Al-Mg, Al-10Si-Cu, Al-10Si-Fe, and Al-10Si-Mg binary and ternary Al alloys, which are among the most commonly used commercial alloys. The thermal and electrical conductivity of the gravity castings of these alloys were measured. The results indicated that when 1 wt% Si, Cu, or Fe was mixed with commercial Al with 99.8 % purity, the thermal conductivity decreased from 213.5 Wm −1 K −1 to approximately 190-210 Wm −1 K −1 . The thermal conductivity remained at a nearly constant level of 154-157 Wm −1 K −1 when the Si concentration exceeded 6 wt% in the Al-Si alloys. Regarding the Al-Mg alloys, the thermal conductivity did not change when the concentration of Mg was increased to 1 wt%. When the concentration of Mg exceeded 1 wt%, the thermal conductivity decreased greatly from 212.

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