The International HIP committee (IHC) presented its ‘HIP Parts of Excellence’ award winners at HIP’14, the 11th International Conference on Hot Isostatic Pressing, Stockholm, Sweden, June 9-13. The Grand Prize was presented to GE Oil & Gas, however Sandvik Powder Solutions, Surahammar, Sweden, also received an award for its quad-metal exhaust valve spindle.
The PM HIP quad-metal exhaust valve spindle is used in large, 2-stroke marine diesel engines manufactured by MAN Diesel A/S and is an outstanding example of how the HIP process can be used to both fabricate shapes and diffusion bond multiple alloys simultaneously.
In this part, the valve stem that serves as a substrate is made of the austenitic stainless steel alloy, SNCrW. As shown schematically in Fig. 1, a HIPed PM nickel-based superalloy Ni49Cr1Nb is used on the valve face to address the corrosive environment within the combustion chamber. Ni40Cr3.5NbTi is used in the valve seat area in order to provide both wear and corrosion resistance, and a layer of 316L stainless steel is used as an intermediate layer separating the SNCrW substrate from the seat and face materials.
All materials except the SNCrW substrate are HIPed Powder Metallurgy materials applied using a proprietary approach. The final sealing of the capsule material to the valve stem is shown in Fig. 2. The large size of these parts is evident.
The nominal composition of the various alloys is shown in Table 1. Fig. 3 shows the three spindles that have been in operation for approximately one year. The valves are removed from the engine periodically and inspected for evidence of corrosion and cracks. To date, the inspections have found no faults in the parts and they are expected to continue in operation for many thousands of hours.