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Vliv legování (10 wt% Mo) a následného zpracování povrchu (laserové přetavení povrchu) na vlastnosti a chování byl hodnocen u PTA návaru oceli M2. Vlivem legování Mo došlo ke změně charaketru a povahy jak matrice, tak karbidů v povlaku M2. Naopak, laserové zpracování vedlo ke zjemnění struktury a potalčení precipitace karbidických částic. Navzdory zvýšení povrchové trvrdosti vykazoval povlak po laserovém zpracování pokles odolnosti proti opotřebení. Naopak, návar legovaný Mo zlepšil odolnost proti opotřebení, ačkoli jeho tvrdost poklesla. Důvodem byla tvorba oxidického tribofilmu typu Magneli v Mo legované oceli. The influence of alloying (10 wt% Molybdenum) and post deposition treatment (Laser Surface Melting) on the structural characteristics and wear performance of Plasma Transfer Arc deposited M2 hardfacings have been investigated. The nature of matrix and carbides of M2 hardfacing had changed upon Molybdenum addition while the Laser Surface Melting caused structural refinement and a decrease in carbide volume fraction. Despite an increase in hardness, Laser Surface Melting has resulted in reduction in sliding wear resistance against alumina counterface, while the Molybdenum enhanced the wear resistance even with decrease in hardness. This counter intuitive behaviour is attributed to Magnelli oxide containing tribo-oxide layer formation on the worn surface of Molybdenum alloyed hardfacings.

The present study evaluates the high temperature sliding wear characteristics of the paste borided 31CrMoV9 and X40CrMoV5-1 steels with respect to the phase structure of the boride layers. Boride layers formed on the surfaces of the examined steels were about 65 μm in thickness and consisted of FeB and Fe 2 B phases. The volume fraction of FeB ( V FeB ) in the boride layers were 31% and 47% for 31CrMoV9 and X40CrMoV5-1 steels, respectively. The testing temperature of 500 °C caused an increment in the wear loss and the friction coefficient for both of the borided steels while their tribological performances were almost similar at room temperature (RT). In association with the presence of low amount of V FeB in its boride layer, borided 31CrMoV9 steel underwent severe wear at 500 °C as the result of heavy cracking on the worn surface when compared to the borided X40CrMoV5-1 steel.

This study focuses on the high temperature tribological behaviour of the boride layers generated on 4140 steel by pack boriding process. Boriding at 750 and 800 °C resulted in a single phase (Fe 2 B) boride layer, while a dual phase (Fe 2 B+FeB) boride layer was developed at 850 and 900 °C. Sliding wear tests conducted by rubbing an alumina ball revealed that single and dual-phase boride layers exhibited almost similar tribological performances and superior wear resistances at room temperature. With increasing testing temperature, boride layers exhibited different wear behaviours depending on their phase structure so that, dual phase boride layer yielded better wear resistance than single phase boride layer, especially at the testing temperature of 300 °C.

Tribological behavior of squeeze cast aluminum alloy (2618, 6082, 7012 and 7075) matrix SiC particle-reinforced (50 vol.%) composites was examined using a reciprocating wear tester by rubbing a 10 mm diameter Al 2 O 3 ball on the composite surfaces in air and in water. Wear tests conducted in air revealed that, at low test loads (≤3 N), the tribological performance of the composites were not remarkably influenced by the properties of the matrix alloy. At high test loads (≥4.5 N), where 7012 and 7075 aluminum alloy matrix composites exhibited superior tribological performance relative to 2618 and 6082 aluminum alloy matrix composites, the wear rate and coefficient of friction decreased with increasing matrix hardness. When compared to the sliding conditions during testing in air, the coefficient of friction and the wear rate of the composites were dramatically lower in water. Even at test loads as high as 24 N, tribological performance of composites tested in water was comparable to that of in air low load (≤4.5 N) testing conditions.

In this study, high temperature abrasive wear behavior of a GGG 40 quality as-cast ductile iron was examined. Wear tests were performed under a compression stress of 5.7 N/mm2, by rubbing the samples (pins) on Al2O3 abrasive grains at various temperatures in between 25 and 600 °C. The examined ductile iron exhibited the highest resistance to abrasion at temperature range between 50 and 100 °C. Tensile tests carried out at 100 °C revealed occurrence of serrated flow on the stress–strain curve, which is the indication of strain aging.

In this study, the effect of retrogression and reaging (RRA) treatment on dry sliding and corrosive wear properties of 7075 aluminum alloy, which was received originally in the T6 temper condition, has been investigated. Retrogression was carried out at four different temperatures between 170 and 380 °C for 60 s. Following the retrogression, alloys were reaged at 120 °C for 24 h. Wear tests were conducted on a ball-on-disc-type wear tester by rubbing Al 2 O 3 balls against the surfaces of the alloys. Corrosive wear tests were carried out in a 30 g/l NaCl+10 g/l HCl solution. Retrogression at 220 and 240 °C improved the dry sliding wear resistance when compared to the T6 temper. However, RRA-treated alloys exhibited higher corrosive wear rate than that of the T6-tempered alloy. Worn surface examinations revealed the wear mechanisms as adhesion for the dry sliding wear and abrasion for the corrosive wear.

In the present study the effect of Hf addition up to 21% on the tribological performance of ZrN coating with the use of reciprocating wear tester was investigated. The coatings were deposited on hardened AISI D2 quality cold work tool steel by Arc-Physical Vapour Deposition technique. Alloying of ZrN with Hf did not change the hardness significantly, where as achieved an improvement on adhesion strength between the coating and the substrate. According to the results of reciprocating wear tests, the wear resistance of the ZrN coating increases with the addition of Hf.

The influence of titanium additions up to 0.38% and heat treatment on the abrasion resistance of a commercial 15% Cr–3% Mo white cast iron were examined. The wear resistance of as-cast commercial alloy was improved about 30% by addition of 0.38% titanium after austenising at 1050°C for 6 h and quenching in air. Tempering of quenched alloys at 250°C for 6 h yielded a decrease in hardness and abrasion resistance relative to the as-quenched condition.