Q. Y. Zhang

Comparative Study of Wear Behaviors of a Selected Titanium Alloy and AISI H13 Steel as a Function of Temperature and Load

A comparative study of the wear behaviors of a selected titanium alloy and AISI H13 steel as a function of temperature and load was performed on a high-temperature wear tester. The titanium alloy and H13 steel presented totally different wear behaviors with the variation in temperature and load. Their behaviors are suggested to be attributed to the protective ability of tribo-oxides and the thermal softening resistance of the matrix. Compared to H13 steel, the titanium alloy presented poor room-temperature wear resistance, excellent high-temperature wear resistance, and an extremely protective function of tribo-oxides.

Relation Between Tribolayers and Wear Behavior During Dry Sliding of Fe-Al Hot-Dipped Coating

ABSTRACT An Fe-Al coating consisting of FeAl and Fe3Al was prepared on AISI 1045 steel by hot-dip aluminizing and subsequent high-temperature diffusion. Dry sliding wear tests were performed for Fe-Al coating against AISI 52100 steel under various sliding speeds and loads. During sliding, thin tribolayers formed on the worn surfaces of the Fe-Al coating. After wear, they were observed to be a nonoxidized mechanically mixed layer (MML) at 0.5 m/s, an oxide-containing MML at 0.75–2.68 m/s, and an in situ oxide layer at 4 m/s. The tribolayers presented a close relation with the wear behavior. Because of their different ingredients, structures, and types, the tribolayers resulted in significant changes in the wear behavior. At 0.75–2.68 m/s (except for 2.68 m/s, 40 N), the compact tribooxide layers exerted a protective function for Fe-Al coating to reduce the wear rate. However, for the tribolayers containing no or trace tribooxides at 0.5 m/s or the unstable ones formed at 2.68 m/s, 40 N and 4 m/s, no protection was presented. In these cases, the Fe-Al coating would be partly or totally ground off, thus presenting poor wear resistance at high wear rates.

Improvement of Thermal Oxidation Resistance of AISI H13 Steel via Hot-Dipped Aluminizing

The aluminized coating on AISI H13 steel was prepared via hot-dipped aluminizing and subsequent high-temperature diffusion. Isothermal oxidation tests of the aluminized and untreated H13 steel were performed. The results showed that the aluminized coating consisting of FeAl and Fe3Al was achieved with Kikendall porosity and carbide particles agglomeration. Compared to the untreated steel, the aluminized steel presented an excellent oxidation resistance and its weight gain slightly increased at 650 and 850°C. At 850°C, the untreated H13 steel had a worse oxidation resistance and the weight gain increased linearly with the increase of oxidation time. Al2O3 was preferentially formed on unspoiled surface and provided a barrier to obstruct the oxygen into the coating, while Fe2O3 formed around cracks had no protection.

Investigation on Elevated-Temperature Wear Resistance of Thermal Oxidation Coating on Ti-6Al-4V Alloy

An oxidation coating on Ti-6Al-4V alloy was prepared by thermal oxidation and subsequent vacuum diffusion. The wear performance of the coating at elevated temperature was evaluated on a pin-on-disc high temperature wear tester under 50-300 N at 400°C. The results showed that the hardened coating with a thickness of 250 μm was produced on Ti-6Al-4V alloy. It was found that the elevated-temperature wear resistance of the coating was remarkably improved, compared with uncoated Ti-6Al-4V alloy. The oxidation coating on Ti-6Al-4V alloy presented extremely low wear losses. The excellent wear resistance of the coating could be attributed to high hardness of coating and its strong bond with substrate. Delamination wear was predominant wear mechanism during dry sliding at 400 °C.

Comparative Study on Wear of Hot-Working Die Steels

The wear behavior and wear mechanism of hot-working die steels H13 and H21 were studied using a pin-on-disc high-temperature wear machine. H21 steel presented higher wear resistance than H13 steel at 25 and 400°C. However the wear rate of H21 steel increased rapidly and was substantially higher than that of H13 steel under a load of 150 N or above at 200°C. Tribo-oxide layer possessing protective effect generated at 200 °C for H13 steel, but appeared at 400 °C for H21 steel with obviously lower amount than that of H13 steel due to relatively high alloy contents. Higher wear resistance of H21 steel is attributed to the undissolved carbides and high thermal strength.