Shengguan Qu

Design and operation of a new multifunctional wear apparatus for engine valve train components

The increasingly strict emission regulations in combustion engines are raising high requirements for the engine valve train system. In this paper, a novel multifunctional wear apparatus is designed to study the performance of engine valve train components. The apparatus employs a mechanical loading system, which consists of a special eccentric wheel and disc springs that apply the combustion loads, and the contact configurations and loading conditions of valve train components are simulated. It has three test functions for different components through specifically designed fixtures. The first function aims to evaluate the interaction between the valve seating face and the seat insert at high temperatures and loads. The second function is used to study the friction and wear properties of the valve stem and the valve guide. The third function is designed to evaluate the performance of the valve seals. At last, a verification test was carried out by the proposed experimental method. A pair of new exhaust valve and seat insert is tested for the performance evaluation of the first function. The wear mechanisms acting on the pairs interface are shown to be a combination of oxidative wear, adhesive wear, as well as fatigue flaking.

Study on High Temperature Friction and Wear Characteristics of 4Cr9Si2 Valve Steel

In order to study the friction and wear characteristics of 4Cr9Si2 valve steel at high temperature, HM1 steel was used as the friction material, and the friction and wear properties of 4Cr9Si2 valve steel under high temperature were investigated on MMU-10G tester. Wear mechanism was discussed. The results show that with the increase of temperature, the friction coefficient and wear amount of 4Cr9Si2 of valve steel are increasing first and then increasing, and the wear amount of the HM1 is increased first and then decreases. 25–200 °C, the friction coefficient and wear amount of the specimens are relatively large, the surface of the specimens was distributed with grooves and adhesive traces, indicating that prevailed wear mechanisms were abrasive wear. When the temperature was between 300 and 500 °C, the friction coefficient and the wear amount are relatively small, convex oxide film appeared on the wear surface, the main wear mechanism were mild oxidation wear and abrasive wear. When the temperature reaches 600 °C, the strength of the specimen decreased obviously, the friction coefficient and the wear amount are sharply increased, and the oxide film on the surface of the friction pair appeared fatigue flake, the predominant wear mechanisms were oxidative wear, abrasive wear and adhesive wear.

Effect of annealing treatment on microstructure and mechanical properties of hot isostatic pressing compacts fabricated using Ti–6Al–4V powder

The effects of annealing temperature and annealing time on microstructure evolution and mechanical properties of Ti–6Al–4V titanium alloy prepared using powder hot isostatic pressing were investigated. The results showed that when annealing temperature was < 1173 K, the globularisation of primary α was observed, and the morphology of secondary α changed from acicular shapes to acicular and continuous lathy grains. Scanning electron microscopy fracture surface showed that the fracture mechanism changed from transcrystalline dimple type to a mixture of transcrystalline and intercrystalline dimple types with increasing annealing temperature. The tensile strength and elongation varied with the temperature in an opposite trend. However, they varied similarly with increasing annealing time. Microhardness was sensitive to the annealing time, resulting into a maximum microhardness of 396.95 HV at 1173 K for 3 h.