The Effect of Water Vapour on the Oxidation of High Speed Steel, Kinetics and Scale Adhesion

Abstract

An investigation has been carried out into the effects of steam on the adhesion of oxide scales grown on four different chemical compositions of high speed steels. The oxidation tests were carried out in a thermobalance at 650°C for up to 14.4 ks. The mass gain of the specimens increased with increasing contents of water vapour, and in no case were parabolic kinetics obeyed. Increasing the alloy chromium content reduced the oxidation rate in dry conditions but increases in the V and W content had no effect. In moist conditions, the alloys containing increased Cr and W had the lowest oxidation rates followed by the alloy with increased V levels, however these effects were small. The ''adhesion'' of the oxide scale was determined using indentation with a Rockwell C diamond and the pull adhesion test to determine the interfacial toughness and the tensile strength of the oxide metal bond, respectively. Generally, the results of the investigation indicated that oxide adhesion was lowest for the specimens exposed to dry conditions, and that with increasing water vapour content, the scale was more adherent. It is noteworthy that whereas the scale formed in dry conditions spalled at the metal oxide interface, that formed in moist gas failed cohesively within the scale, mostly at the Cr spinel/ magnetite interface. Examination of the fractured scale after indentation shows that the outer oxide layer became more porous as the water vapour content of the gas increased. Indentation test results showed that an increase in the V concentration was deleterious to oxide adhesion in both the dry and wet environments, whereas an increase in the Cr-content had little effect on adhesion. The results with the pull test were less clear.

Effect of selective oxidation and sulphur/phosphorus‐containing compounds on coking behaviour during light naphtha thermal cracking

“…Figure shows that the oxide compound scales mainly consist of blade‐like oxides. As reported previously, this type of oxide formed when the oxidation atmosphere contained water vapour.…”

Mechanisms of Oxidation Degradation of Cr12 Roller Steel during Thermal Fatigue Tests

“…In some cases, carbides could oxidize faster than the matrix, depending on the local chemical composition, which complements the observations of Kim et al [34]. Large oxidation tongues in the present study contrast with oxidation studies [4,15,22,23,28,[34][35][36][37][38] and tribological tests [3,[9][10][11]14,16,25,26,33,35,[39][40][41][42][43][44][45][46][47][48][49][50][51][52][53][54][55][56][57]. This is attributed to test conditions where thermal cycles play an important role in O diffusion and confirms the theory of Lao et al [27] that the condition under isothermal testing in the highly plastic deformed region during sliding wear is not comparable to the behavior during hot rolling.…”

“…Due to the cooling water used in rolling mills, some materials show significant surface deterioration not only due to thermal cycles but also due to oxidation. In the available scientific literature, the oxidation phenomena are mainly discussed by classical oxidation studies in humid atmospheres and under isothermal conditions [4,15,22,23,28,[34][35][36][37][38]. Since thermal cycles with water cooling stress the material in each cycle, a direct comparison is very difficult.…”

“…It is generally very complex, as temperature, time, environmental conditions and microstructure are intertwined [3,. The oxidation behavior of roller material at high temperatures was investigated by oxidation studies [4,15,22,23,28,[34][35][36][37][38], tribological tests [3,[9][10][11]14,16,25,26,33,35,[39][40][41][42][43][44][45][46][47][48][49][50][51][52][53][54][55][56][57] and thermal fatigue tests [5,6,12,[29][30][31]. The tribological tests were performed with disc-on-disc tests [3,[9][10][11]…”

“…Numerous oxidation studies have been performed in different atmospheres at high temperatures [4,15,22,23,28,34,[36][37][38]. Different oxidation rates of the matrix and the carbides were determined depending on the test temperature, the material, the carbide properties and the atmosphere (oxidation conditions).…”