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).
Micro-examination report on three separate samples of nitrided alloy steel.
| Identifier | ExFiles\Box 154a\1\ scan0144 | |
| Date | 15th March 1929 | |
| Micro-examination Report. M.649. To-HS{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer} from H1. c. R.{Sir Henry Royce} c. Wor.{Arthur Wormald - General Works Manager} c. By.{R.W. Bailey - Chief Engineer} c. Rg.{Mr Rowledge} c. E.{Mr Elliott - Chief Engineer} c. DA.{Bernard Day - Chassis Design} H1.1/AG.15.3.29. NITRO ALLOY STEEL. (Your ref: Hs{Lord Ernest Hives - Chair}/Rm{William Robotham - Chief Engineer}2/LG.4.2.29.) Three separate samples of nitrided steel have now been tested in the laboratory, and it will probably make the position clearer, if we recapitulate the main points of our previous reports in addition to giving the results of our latest investigation. The first sample submitted was from Messrs. Firth - Derihon and consisted of a number of test bars suitable for various mechanical tests. The nitrogen case on these bars proved in all the tests applied to be exceptionally brittle, there being a great tendency to spalling and cracking of the surface layers. In this respect it differed from any steel we had previously tested, carburised or otherwise. Several photomicrographs of this sample were taken. It was shown that a white layer, approx. 0.003" deep, was chiefly responsible for the flaking of the outside of the case. This layer also contained a thinner grey layer approx. 0.0003" thick, and about 0.0003" below the outer surface of the case. Beneath the white layer, and apparently of the same constituent were white wavy lines, these being distributed through the greater part of the case. The chief points to note here are the presence of the grey layer, and the fact that the removal by grinding of the whole of the white layer, almost, if not entirely, eliminates the spalling and cracking. The grey layer was not reproduced on nitriding some of the steel ourselves, and thus it appears that the presence is due to Messrs. F.Ds. nitriding procedure. The second sample received was the half cylinder liner from Messrs. Hispano - Suiza. This was quite different from the first sample in that it had no tendency to crack or spall. It is interesting to note that under the Rockwell test this case deflected heavily but showed no signs whatever of cracking or breaking away. This degree of toughness is equal to that of carburised nickel steel, but it has considerably greater hardness, and probably possesses a correspondingly greater resistance to wear, than that produced by carburising. continued. | ||