From the Rolls-Royce experimental archive: a quarter of a million communications from Rolls-Royce, 1906 to 1960's. Documents from the Sir Henry Royce Memorial Foundation (SHRMF).
Investigation into the unsatisfactory results of nitriding austenitic steel cylinder liners for Kestrel engines.
| Identifier | ExFiles\Box 154a\1\ scan0260 | |
| Date | 7th June 1932 | |
| To R.{Sir Henry Royce} from RHC.{R. H. Coverley - Production Engineer} c. to Wor.{Arthur Wormald - General Works Manager} Rg.{Mr Rowledge} c. to By.{R.W. Bailey - Chief Engineer} E.{Mr Elliott - Chief Engineer} X1474 RHC.{R. H. Coverley - Production Engineer}2/BE.7.6.32. x3866. AUSTENITIC CYLINDER LINERS. Some time ago, a set of drawn tube austenitic steel cylinder liners for Kestrel were supplied by the Chesterfield Tube Co. In order to obtain some experience with this material, one liner was machined in advance to test out on Kestrel single cylinder unit. Nitriding was carried out at a temperature of 550°C over a period of 90 hours, distortion of bore being in the region of .005" to .006" (which exceeds the amount experienced on nitralloy material) therefore it was necessary to regrind the bore. On examination it was found that the material had not wholly responded to the nitriding treatment, there being soft and hard patches on the nitrided surface. It was not realised that the necessary grinding to remove distortion would also remove the hardened surface until the completion of a one hour run on the Single Cylinder Unit when both cylinder liner and pistons were badly scored. Liner was cut up for Hardness tests, Brinell figure being 187 to 210 as compared with standard material S/HC which gives a Brinell of 255 to 285. Therefore, before proceeding with further liners, it was decided to carry out a series of tests with test pieces of similar material, which revealed that nitriding only penetrated to a depth of .001" to .002", which accounted for the scoring experienced on the liner fitted to the Single Cylinder and also confirmed that the material did not really respond to the nitriding treatment. Hl. considered that if this material was electro-copper plated it would more readily respond to nitriding. Three liners were therefore prepared and along with test pieces were despatched to the Sheepbridge Stokes Co. for nitriding. This condition did not produce the desired results, as the nitriding had only penetrated to a depth of .001" and the Brinell figure varied from 300 to 650, which confirmed our earlier impressions of the hard and soft patches on the nitrided surface. So far, it has been found impossible to satisfactorily harden austenitic steel. The matter, however, is being further investigated by the manufacturers, and until their recommendations are available, it is hardly worth while proceeding with the remaining liners which are in hand at our Works. R.H.C. | ||