摘要:

AbstractCrNand (Ti, Al) N coatings have been deposited by high rate sputter deposition. CrN is one of the most uncritical coatings to produce, neither microhardness nor sputtering stability being influenced by sputtering conditions. Depending upon the nitrogen partial pressure during deposition and the aluminium content, (Ti, Al) N coatings with maximum microhardness values of 2200–3000 HV0.01 can be obtained. Such coatings have superior oxidation and wear resistance compared to normal sputtered TiN coatings.

ISSN:0267-0844    

DOI:10.1179/sur.1987.3.1.47

出版商:Taylor&Francis    

年代:1987

数据来源: Taylor

摘要:

AbstractA screw fed, gravity flow, carrier gas aided powder delivery system was used to produce laser surface alloys using chromium and nickel powders on AISI 1016 steel. A 10 kW continuous wave CO2laser was used for alloying, at incident power densities up to 1.2×1010W m−2and traverse speeds up to 0.03 m s−1. Ten overlapped passes were used to make alloyed zones 0.05 m long by 0·015 m wide. Alloys with up to 80 wt-%Cr and 58%Cr + 26%Ni were obtained. Surface roughness and corrosion resistance measurements were made. The microstructure was characterized by transmission and scanning electron microscopy. Smoother surfaces were obtained by increasing traverse speed and beam diameter. Corrosion samples passivated spontaneously in a 3.5%NaCI solution in distilled water, but were susceptible to pitting corrosion when uneven su;faces were subjected to corrosion testing. Microstructures were highly refined with a high dislocation density. These results are related to process mechanisms. The reported method of powder delivery is versatile, flexible, and reproducible, and can be used to make useful alloys.

ISSN:0267-0844    

DOI:10.1179/sur.1987.3.1.53

出版商:Taylor&Francis    

年代:1987

数据来源: Taylor

摘要:

AbstractResidual stresses in chemically vapour deposited (CVD) TiC and TiN coatings on various substrates were measured using X-ray diffraction. A quantitative prediction of the vaiue of the strain (and stress) was obtained from the difference in thermal shrinkage between layer and substrate on cooling from the CVD temperature to room temperature. The sign of the strains measured always agreed with the prediction, but in a number of cases the absolute value of the elastic strain measured was smaller than that predicted. For layers on iron and Fe-1.0 wt-%C substrates this difference is caused by strain accommodating processes in the substrate, mainly during phase transformations. For TiN layers on molybdenum and tungsten substrates, strain accommodating processes occur in the layer, and these may originate in the microstructure of the layer.

ISSN:0267-0844    

DOI:10.1179/sur.1987.3.1.59

出版商:Taylor&Francis    

年代:1987

数据来源: Taylor

摘要:

AbstractPeening is a technique commonly used to improve fatigue resistance, but it is not always appreciated that excessive peening may be detrimental to fatigue behaviour. The present work demonstrates this effect in three different alloys: a mild steel, stainless steel, and a commercial copper alloy. The dependence of fatigue behaviour on peening intensity is shown to reach a maximum beyond which high intensity peening reduces fatigue life; at very high intensities the fatigue life can be reduced below the unpeened value. This reduction in fatigue life is shown to coincide with an increase in surface roughness, as measured by the parameter Ra, and the onset of a distinct damage mechanism revealed by scanning electron microscopy. The varying effect of peening intensity in the different materials is related to their tensile, fatigue, and wear properties; a model is advanced to explain the observed behaviour, based on the change from an initiation dominated mechanism to a propagation dominated mechanism as peening intensity is increased. A limited number of results is also presented showing the effect of peening time on fatigue behaviour.

ISSN:0267-0844    

DOI:10.1179/sur.1987.3.1.64

出版商:Taylor&Francis    

年代:1987

数据来源: Taylor

摘要:

AbstractMicrohardness indentation of thin PVD wear resistant films usually results in deformation of both the coating and the substrate and such tests lead to a‘composite’hardness number. Previous attempts at separating the contributions from coating and substrate to measured hardness will be reviewed and a new thin layer hardness model proposed. Examples of the use of this model for the determination of‘true’coating hardness will be given. These include an investigation of the effects of substrate bias on hardness of ion plated titanium nitride and the modelling of the hardness behaviour of soft nickel coatings and ion bombardment amorphized silicon.

ISSN:0267-0844    

DOI:10.1179/sur.1987.3.1.69

出版商:Taylor&Francis    

年代:1987

数据来源: Taylor