The wear and fatigue behaviours of hollow head & sodium filled engine valve

Abstract

Increasing performance requirements of IC engines often leads to higher combustion chamber temperatures that cause premature failure of exhaust valves. This paper presents a tribological assessment of hollow head & sodium filled valves (HHSVs) produced using a new manufacturing process. Tests were conducted using bespoke bench-top wear and fatigue apparatus, and the HHSV specimens survived defined durability tests. When compared to traditional solid valves, the highest temperature of the hollow stem & sodium filled valves decreased from 745 °C to 590 °C. It was established that the new process did not adversely affect the wear mechanisms (oxidation accelerated adhesion) and the material loss magnitude when compared to solid valves. The design of HHSVs tested gives a 16.1% reduction in mass.

Optimization of Friction Welding Process Parameters for 42Cr9Si2 Hollow Head and Sodium Filled Engine Valve and Valve Performance Evaluation

“…Huaiji Dengyun Auto-parts (Holding) CO., LTD. (HJ company) has invented and proposed three manufacturing methods for HHSVs in recent years, as presented in the two authorized Chinese patents of the HJ company and previous works of Lai et al [7]. The schematic diagram of the main steps of each method is illustrated in Figure 2.…”

“…The third method is referred to as the “hollow engine valve drilling and friction welding manufacturing method” [7], as presented in Figure 2c. The method has seven manufacturing processes: (1) preparation of solid bar workblank; (2) upsetting for a bigger solid end; (3) punching on bigger end for hollow valve head; (4) hollow stem valve drilling; (5) sealing at hollow valve head by friction welding; (6) filling sodium and then sealing at hollow valve stem by friction welding; and (7) valve seating face hardfacing and completion of machining.…”

“…Three HHSV specimens named A, B and C were tested at different conditions in this work. In addition, the results of two HHSVs made of 33Cr23Ni8Mn3N (23-8N) steel reported in previous research of Lai et al [7] are given for a comparison. Table 6 presents the properties and configurations of these five HHSVs.…”

“…Hence, surface enhancement should be applied to improve the wear resistance of the valve seating face. As presented in Figure 18b, compared to valve 2 it had no hardfacing material, and the seating face of valve 4 which was hardfaced with Stellite F alloy had a much better wear resistance [7].…”

“…An investigation of HHSVs manufactured from 33Cr23Ni8Mn3N (23-8N) austenitic engine valve steel has been reported in previous work of Lai et al [7], however, the friction welding process was not detailed. In this paper, investigations of HHSVs manufactured of 42Cr9Si2 martensitic engine valve steel were conducted, especially, the optimization of the friction welding process.…”