Jan Jozef Schreurs

Friction and wear properties of nitrided and N+-implanted 17-4 PH stainless steel

Abstract N + implantation of thermally nitrided 17-4 PH stainless steel substantially improved friction and wear properties in lubricated sliding wear tests. Some improvement was also obtained by nitriding or by N + implantation alone. Auger and surface topography analyses of specimens before wear testing indicated that the improved wear performance may be due in part to the implantation of carbon, and perhaps oxygen, when N + was being implanted under a relatively high target chamber pressure and in part by the topographical alteration of the surface in thermal nitriding.

Evidence of supersonic flow in an arc-heated diamond film deposition reactor

Abstract A Pilot impact tube was used to measure the flow velocity in a laboratory d.c. arc-heated diamond deposition reactor at 35 Torr. Speeds up to Mach 1.32 ± 0.09 were found, with the bracketing error in the measurement representing alternative interpretations according to equilibrium or frozen chemistries. Radial traverse across the reactor showed peak Mach numbers along the centerline, as expected for a free jet into a relatively stagnant ambient. As the surrounding fluid is entrained, it slows the jet, cools it, and spreads it out, such that the centerline Mach number at the substrate location drops to M ≈0.3. Theory has indicated that optimal diamond film growth rate and quality will result in arc jet reactors if the Mach number is around sonic, M = 1. Here we have tested the flow field downstream of an arc jet issuing from a converging-diverging nozzle, establishing experimentally that regions in our diamond reactor indeed have M > 1. We believe that this is the first reported experimental measurement of such a high velocity in a diamond reactor.

On-line valve monitoring and diagnosis

A valve monitoring system that enables the selection of power plant steam and containment valves to be serviced to be made on a justifiable priority-of-need basis is described. The system is designed to assist utilities in increasing plant availability and in decreasing maintenance costs attributed to valving. The system operates in one of two modes: trending or single-stroke. In the trending mode, the system monitors the performance of critical valves while the plant is online and compares sensor data with baseline signatures. Deviations from baseline data are evaluated by an expert system, and when the deviations exceed caution levels, probable causes of trouble are identified. In the single-stroke mode, the system is hooked up to any valve when the plant is offline and the valve is cycled through one full stroke (opening and closing). Using engineering data for the valve, the sensor signals are analyzed and a diagnosis is made.<<ETX>>